V OL U M E 5 6 NUMB ER 3 , 2 0 01

ICAOJ O U R N A L

Data link simulations highlight benefits

SAFETY FIRST:P ro ficiency in a common ATC language

SAFETY FIRST:P ro ficiency in a common ATC language

APRIL 2001VOL. 56, NO. 3

ICAO Jou rnal

FEATURES5 ATM projects now under way in Europe may have far-reaching implications

for concepts such as free flight.

10 Simulations indicate that implementation of data link services has a beneficialeffect on controller workload as well as potential safety gains.

15 A fleet of light aircraft is being equipped for a real-world evaluation of the safety benefits arising from the use of advanced technologies.

20 The opening of a new air route structure over the North Pole promises significant reductions in flight times and cost.

24 A study group is examining ways to strengthen provisions for English languageproficiency among ATC personnel and flight crews.

27 Technological innovations are having a positive impact on search and rescueservices, but also redefine the scope for human error.

30 Safety issues highlighted by report on TWA Flight 800 include fuel tank flammability, fuel tank ignition sources, and design and certification standards.

ICAO UPDATE34 Environmental colloquium facilitates exchange of views; ICAO releases

preliminary safety statistics for the year 2000.

COVERMost of our feature articles this month focus on air traffic management, including anarticle on the need to strengthen provisions for proficiency in a common aviationlanguage (see page 24). The potential consequences of an aviation mishap as a resultof ambiguous communication or lack of language proficiency are serious enough thatexperts are reviewing ways to address the issue as a matter of priority.Cover photo courtesy of The Boeing Co.

The magazine of the International Civil Aviation Org a n i z a t i o n

THE ICAO COUNCILP re s i d e n tD r. ASSAD K O TA I T E1st Vi c e - P re s i d e n tS.W. GITHAIGA2nd Vi c e - P re s i d e n t–3 rd Vi c e - P re s i d e n tS.N. AHMADS e c re t a ryR. C. COSTA PEREIRA

S e c re t a ry General

ALGERIAT. ChérifARGENTINAJ.L. BacarezzaAUSTRALIAJ. AleckBOTSWANAK.J. MosupukwaBRAZILA.M. CunhaCAMEROONT. Te k o uCANADAG. RichardCHINAY. ZhangCOLOMBIAJ.M. Pulido UribeCUBAM. Molina MartínezEGYPTM.A.A.A. ElbagoriFRANCEJ.-F. DobelleGERMANYDr. H. MürlINDIAA.P. SinghINDONESIAJ. Sjioen ITALYG.L. CornadoJAPANA. AokiKENYAS.W. GithaigaLEBANONR. AbdallahME X I C OR. Kobeh GonzálezNETHERLANDSM.A. KraanNI G E R I AD.O. EniojukanNORWAYO. M. RambechPA K I S TA NS.N. AhmadPA N A M AR.E. García de ParedesRU S S I A N FE D E R AT I O NV.P. KuranovSA U D I AR A B I AS. Al-GhamdiSE N E G A LB. GueyeSLOVAKIAO. FabriciSPA I NL. AdroverUN I T E D KI N G D O MD.S. EvansUN I T E D STAT E SE.W. StimpsonUR U G U AYC.A. Borucki

Editor: Eric MacBurnie Production Clerk: Sue-Ann RapattoniEditorial Assistant: Regina Zorman Design Consultant: Rodolfo Borello

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fined separation of three nautical miles(NM) from the lead aircraft, a pro c e s sthat is similar to today’s visual appro a c hp ro c e d u res during visual meteoro l o g i c a lconditions (VMC). The dif f e rence in thiscase is that surveillance information is made available electronically to thepilots, thus allowing VMC-like pro c e-d u res to be applied during instru m e n tm e t e o rological conditions (IMC).

The DAS simulation clearly demon-strated that station-keeping in the arr i v a lphase contributes to a significantlyi n c reased capacity in air traf fic andreduced ATC workload. This is a typical

example of how new pro c e d u res basedon new techniques can be applied to airt r a ffic management (ATM) in order tofulfil the goals defined by the ICAOC N S / ATM concept. The new techniquein this example is automatic dependents u rv e i l l a n c e - b roadcast (ADS-B).

What is ADS-B?Automatic dependent surveillance is

one of the new features introduced bythe ICAO CNS/ATM concept. It wasdeveloped as a new means for surv e i l-lance, filling the gaps in the traditional

g round-based surveillance systems whicha re limited by line of sight. A data link isused to provide ATC with airc r a f t - d e r i v e ddata such as position and intent.

Long range data communications usingthe aeronautical mobile-satellite serv i c e(AMSS) and high frequency (HF) data linka re available today to support operationsover areas lacking adequate ground infra-s t ru c t u re. These systems provide aero n a u-tical telecommunication network (AT N )compatible air-ground data link. In princi-ple, any ATN compatible air-ground datalink can be used to support ADS, includ-ing very high frequency (VHF) digital link

(VDL). The initial version of ADS, calledADS contract (ADS-C), is based on point-to-point communications between applica-tions on-board the aircraft and on theg round, and can only support traditionalg round-based surveillance functions. Atp resent, ADS-C is used as a re p l a c e m e n tfor voice position re p o rts over the Atlanticand the Pacific .

A D S - b roadcast evolved as a new func-tion providing surveillance data to flightc rews as well as ATC. With ADS-B, sur-veillance data broadcast from aircraft aswell as by airport ground vehicles can be

N aircraft is being sequencedbehind another on its appro a c h

to Stockholm’s Arlanda Airport ,with an unusual exchange between theair traffic controller and pilot.

ATC: “Scandinavian 123, Point out,Delta Lima Hotel 456 at one o’clock,keep 3 NM target trail.” Pilot: “3 NM target trail Delta LimaHotel 456, Scandinavian 123.”Pilot: “Delta Lima Hotel 456 in sight atone o’clock distance 6, Scandinavian1 2 3 ”P i l o t : “Locked on 3 NM target trailDelta Lima Hotel 456, Scandinavian1 2 3 . ”ATC: “SAS123, keep separation.”

The above communication betweenpilot and controller is taken from a sim-ulation of delegated airborne separation(DAS) which took place at the SwedishATS Academy (SATSA) in Malmö,Sweden on 19-20 May 2000. The simula-tion, focusing on the approach andclimb-out phases of flight, was based onthe new thre e - runway configuration atthe Stockholm Arlanda Airport and wasp e rf o rmed by using an air traffic contro l( ATC) simulator manned by operationalc o n t rollers. In the above communicationexample, separation between two airc r a f ton approach is established and main-tained by ATC. After initiation of a pro-c e d u re known as station keeping, thea i rc rew of the trailing aircraft acceptsresponsibility for maintaining the de-

AIR TRAFFIC MANAGEMENT

ATM projects in Europe may have far- re a c h i n gimplications for concepts such as free fli g h t

A number of re s e a rch projects that use emerging satellite, air- and ground-based technologies to support a future ATM concept are in pro g ress worldwide, including several in Europe that a re based on ADS-B supported by VDL Mode 4.

LA R RY JO H N S S O N

LU F T FA RT S V E R K E T

( SW E D E N)

5NUMBER 3, 2001

Cockpit displays featuring moving airport map and ground track representation,left, and flight plan, moving map and CPDLC information, right.

A

with other traf fic. This arr a n g e m e n tmakes it possible to utilize the airspacem o re eff i c i e n t l y.

ICAO has developed two sets of com-p l e m e n t a ry standards supporting ADS-B.The Secondary Surveillance Radar Im-p rovements and Collision Av o i d a n c eSystems Panel (SICASP) developedMode S extended squitter as an enhance-m e n t of the airborne collision avoidancesystem (ACAS), while the Aero n a u t i c a lMobile Communications Panel (AMCP)developed VHF digital link Mode 4 ins u p p o rt of surveillance applications.

A collision avoidance system is thelast safety net, and is supposed to

p revent collision whenother measures for pro-viding aircraft separa-tion have failed. It istypically based on therapid exchange of posi-tion data within shortranges. ASAS applica-tions are based onexchange of data overlonger ranges in sup-p o rt of the orderly flowof air traf fic that is char-acteristic for air traff i cmanagement. For safetyreasons, it is import a n tto maintain a clear divi-sion between these two

functions. There f o re, the collision avoid-ance system should not be based on sametechnology as other ATM functions.

The availability of surveillance data inthe cockpit will allow the airc rew to takea more active role in the ATM pro c e s s .With this information on hand, it will bepossible for pilots and controllers tos h a re separation tasks in a new way.

ADS-B is expected to become one ofthe cornerstones of ASAS. The availabili-ty of surveillance data in the cockpit isone of the most significant impro v e m e n t smade in aviation in the past 50 years.

System development Tr a d i t i o n a l l y, systems on board air-

craft and systems on the ground havetheir own lives and have been developed

i n d e p e n d e n t l y. They emerged as uniquesolutions for aviation, strictly within oneof the three domains: communications,navigation or surveillance (CNS).

The main on-board navigation system,the flight management system (FMS),exists in many diff e rent versions and lev-els of sophistication. Emerging versionsp rovide the airc rew with advanced toolsfor optimum operation of the aircraft ina c c o rdance with parameters set by thepilot. These tools will make it possible toachieve the perfect balance betweeneconomy and perf o rmance for the spe-cific flight. The FMS gives the pilot totalc o n t rol over the aircraft and its flight tra-j e c t o ry, allowing arrival over waypointswith an accuracy of within a few seconds.

Scandinavian Airlines System (SAS)and the Swedish company, AVTECH, incooperation with FMS manufacture rSmiths Industries, are currently con-ducting a study to investigate the accu-racy of touchdown time pre d i c t i o n smade prior to take-of f. The companiesanticipate it will be possible to pre d i c ta rrival time to within 10 seconds. FMScapabilities make it possible for the air-c rew to agree on very precise contractswith ATC, provided that appro p r i a t eoperational pro c e d u res are put in place.

The present ground-based ATC sys-tems, based on radar technology and air-craft positions having an accuracy ofh u n d reds of metres and flight plan sys-tems that define timing in minutes, notseconds, are limiting the possibilities ofs u p p o rting accurate planning and confli c tdetection. Early and accurate planning isone of the key elements in the ATM sys-tem envisaged in the CNS/ATM concept.With today’s ATC system, it is not possi-ble to take advantage of the capabilities ofa modern aircraft with an advanced fli g h tmanagement system. More o v e r, for sys-tem consistency, all phases of flight haveto be included in an accurate planningp rocess, from gate-to-gate or en-ro u t e - t o -e n - route, as some prefer to describe thep rocess to better re flect that aircraft turn -a round time is included.

To d a y, the only “technical” connectionbetween airborne and ground-based sys-

received and used by any pro p e r l yequipped user. In ATC centres it is pos-sible to present ADS-B data in a form a tresembling today’s displays of radardata. ADS-B data is useful as a comple-ment to radar information, and in are a swithout radar infrastru c t u re it can pro-vide radar-like functionality, hence elimi-nating the need to pro c u re radar systemswhen traffic gro w s .

A surveillance picture based on ADS-Bcan be presented to the pilots on a cock-pit display of traffic information (CDTI).As ADS-B is transmitted by means of adata link, other data link functions canalso be supported. These may include a

two-way exchange of intent inform a t i o n ,downlink of aircraft parameters (DAP),uplink of surveillance inform a t i o nderived from other surveillance systems(TIS-B), uplink of weather and flighti n f o rmation (D-FIS), and contro l l e r – p i l o tdata link communications (CPDLC).Such varied information can be transmit-ted on the same or more data links.

The two types of automatic dependents u rveillance, ADS-B and ADS-C, com-plement one another. In areas withoutg round infrastru c t u re, ADS-C can pro-vide ATC with the information neededfor the sur veillance functions, while air-b o rne separation assurance system(ASAS) applications based on ADS-Bwill allow the flight crew to assumeresponsibility for maintaining separation

AIR T RAFFIC MANAGEMENT

ICAO JOURNAL6

The Swedish ATS Academy at Malmö, Sweden is equippedwith an advanced multirole ATM research and trainingsimulator known as SMART, which is capable of assessingscenarios involving up to 500 simultaneous flights.

E u ro c o n t rol, in line with its “AT M2000+” strategy for Europe, is develop-ing a cooperative ATS (COOPATS) con-cept. This is a concept of air traff i cmanagement that enhances the pro d u c-tivity and safety of air traf fic serv i c e s( ATS) through the optimum involvementof controllers, airc rew and airlines byusing integrated data communicationsand improved forms of surveillance andautomation. The aim is to support con-t rollers, pilots and all potential AT M

users in all phases offlight and eventuallyachieve autonomousflight operations in“ f ree flight” airspace.This can be accom-plished by pro g re s-sively implementingfully seamless com-munications, data ex-change, situational awareness andautomation capabilities, together withassociated pro c e d u res and ru l e s .

This initiative is closely coord i n a t e dwith the work of the Euro c o n t rol ADSp rogramme, which is developing an oper-ational concept and re q u i rements forADS (including both ADS-C and ADS-B)as well as developing a transition plan fori n t roducing ADS in Europe supported bysafety and cost-benefit analyses.

New facilities will probably first bei n t roduced in areas lacking surv e i l l a n c e

functions today. In other areas, new func-tions will complement the traditional func-tions. The ATM system will continue toevolve when confidence is gained in thenew technologies, techniques and pro c e-d u res. In other words, the introduction ofnew technology will be incre m e n t a l .

R&D pro j e c t sA number of projects using emerg i n g

satellite, air and ground technologies tos u p p o rt a future ATM concept are ongoing

worldwide. Several large-scale Euro p e a np rojects focus on the use of data links tos u p p o rt a range of user applications andscenarios across the CNS domains. Someof the achievements of these projects mayhave far-reaching implications for thedevelopment of future ATM systems andconcepts such as cooperative air traf f i cs e rvices and free flight. All of theE u ropean programmes, described brieflyb e l o w, are based on ADS-B supported byVDL Mode 4.

NEAN update pro g r a m m e. The NEAN

tems is the secondary surveillance radar(SSR) transponder that provides for limitedexchange of data. Data links are stillv e ry rare in ATC and provide only basics e rvices such as pre - d e p a rt u re clear-ances, weather and position re p o rts overremote areas through ADS-C. To achievethe real benefits expected from the newtechnologies, applications on-board air-craft and applications in the gro u n d - b a s e dATM systems have to be developed inclose cooperation. Accurate aircraft per-f o rmance, contracts reached byc o n t rollers and pilots, and trans-p a rent data exchange betweeng round-based and airborne sys-tems, are some of the key feature sin the emerging systems.

Operational implementationImplementation of the ICAO

C N S / ATM systems is ongoing.The technical components area l ready in place or are in thep rocess of being standard i z e d .They will form the technical foun-dation for aviation in the timeframe 2010-15. Systems not yets t a n d a rdized will not be availablein this time frame.

ADS-B is often considered to be oneof the key enablers for the CNS/AT Msystems. There are several reasons whythis is the case: as stated pre v i o u s l y,ADS-B consists of elements from allt h ree CNS domains. It provides theflight crew with better situational aware-ness, and provides ATC with accuratea i rcraft-derived data. What’s more, theCNS elements are available for otherATM applications.

To benefit from the new technologicalsystems, both the operational workingmethods and the legal framework willhave to be adjusted. Various groups ofe x p e rts are working on defining detailsof the future concept, developing opera-tional pro c e d u res and defining newapplications. When ground and airborn esystems are linked together technicallyin a transparent way, the operational pro-c e d u res and applications will have to bedeveloped jointly.

AIR TRAFFIC MANAGEMENT

7NUMBER 3, 2001

Displays based on ADS-Bimprove situational aware-ness for operators ofground vehicles as well asthe tower controller andpilot. The situation dis-plays featured here areinstalled in a ground vehi-cle based at the StockholmArlanda Airport, the ArlandaAirport control tower anda SAS Fokker F28.

g round and airborne equipment will bereplaced by cert i fiable equipment compli-ant with ICAO standards. The upgradedi n f r a s t ru c t u re will enable continued andi m p roved support for activities perf o rm e din other projects, and will allow the VDLMode 4 ground network to be expanded.

NUP objectives include the develop-ment of an operational concept for ADS-Bbased ATM, and the identification, inves-tigation and development of re l a t e dapplications. With the addition of theD i rectorate General of Civil Aviation ofFrance and Airbus Industrie/Aero s p a-

tiale, NUP includes the same core part-ners as NEAN and NEAP.

The programme is proceeding in coor-dination with the Euro c o n t rol ADS pro-gramme. The first phase of NUP will becompleted by mid-2001 and will be fol-lowed by a second phase, with the objec-tive of establishing a European ADS-Bnetwork “based on global standards sup-p o rting certified applications and equip-ment in synergy with the European AT Mconcepts providing benefits to AT Ms t a k e h o l d e r s . ”

The schedule calls for stand-alone,local implementations to be in place in2003 and fully integrated Euro p e - w i d eimplementation to be achieved in 2006.In phase II, more partners and a newa rea of special interest, integration withATC systems, will be added.

The core element of NUP is the oper-ational development team. These expertteams, consisting of pilot, ATC, airport ,general aviation and industry re p re s e n-tatives, are called “Tiger Teams”. Ino rder to cover diff e rent phases of flightand ATM environments, seven suchteams have been established thro u g h o u tE u rope. Each has its own specific task.The aggregated development work per-f o rmed by the teams, whose activitiesa re described briefly below, forms thebasis for analysis of operational and costb e n e f i t s .

Tiger Team Stockholm. T h eteam leader SAS is, together withATC and Stockholm Arlanda Air-p o rt Authority, investigating thepossibilities of using ADS-B fori m p roved approach and depar-t u re pro c e d u res. The basic con-cept is called “station keeping”.The anticipated benefits includea 20 to 30 percent increase ind e p a rt u re and arrival capacity.

Tiger Team Copenhagen. T h eDanish CAA is leading a teaminvestigating the use of ADS-Bfor helicopter traf fic in theN o rth Sea. This environment isp robably one of the mostdemanding in commercial avia-tion. The main objective is to

i m p rove safety and regularity for the hel-icopter traffic between the mainland ando ff s h o re oil rigs in non-radar airspace.

Tiger Team Frankfurt . Led by Luf-thansa, this team is investigating thepotential of using improved situationa w a reness based on ADS-B during thea rrival and approach phase, calledenhanced visual acquisition (EVA ) .E l e c t ronic means (i.e. CDTI) are used toa c q u i re preceding traffic. It is anticipat-ed that airborne visual separation could

update programme (NUP) is a follow upof the North European ADS-B network(NEAN) project, which was sponsore dby the European Commission (EC) andcompleted in 1999. In NEAN, ADS-Bcapability was created through a net-work of ground stations and mobile pro-totype VDL Mode 4 equipment installedin commercial aircraft and airport vehi-cles. The network is still in place andextends over Denmark, Sweden, Ger-many and beyond, providing VHF cover-age for data link communications acro s sa large part of nort h e rn Europe. Positionre p o rts received by a gro u n dstation are distributed thro u g h-out the network to ATC and toother users.

The air and ground infrastru c-t u re created by NEAN compris-es some 15 ground stations, 25equipped commercial airc r a f t ,and some 30 airport vehicles.NEAN was a collaborative ven-t u re between the Swedish, Ger-man and Danish civil aviationadministrations with the activep a rticipation of Lufthansa, SASand regional airlines. After at ime, the NEAN i n i t i a t i v ef o rmed the baseline concept i nthe North Atlantic ADS-B net-work (NAAN).

NEAN provided the infrastru c t u re forthe extensive testing of specific CNS/ AT Mapplications conducted in other pro j e c t ssuch as the North European CNS/AT Mapplications project (NEAP), also com-pleted in 1999. In NEAN, the followingapplications were evaluated:• enhanced surveillance through thedownlink of aircraft parameters;• pilot situational awareness in flight andon the gro u n d ;• global navigation satellite system(GNSS) precision navigation capabilityfor en-route and appro a c h ;• extended helicopter surveillance inN o rth Sea operations; and• runway incursion monitoring.

The NEAN update programme, NUP, isupgrading the ADS-B infrastru c t u re cre-ated by NEAN. Prototype VDL Mode 4

AIR T RAFFIC MANAGEMENT

ICAO JOURNAL8

Larry Johnsson is the Senior Systems Engineer/ Pro-grammer in the Air Navigation Services Division of theSwedish Civil Aviation Administration (Luftfartsverket),and works from the ATC Systems Logistic Office inMalmö-Sturup, Sweden. He has been a member of theICAO Aeronautical Mobile Communication Panel(AMCP) since his nomination by Sweden in 1994. Mr.Johnsson may be contacted by fax at 46 40 6131378 or46 708 151382 or email (larry. j o h n s s o n @ l f v. s e ) .

continued on page 37

In recent years ADS-B has been used to improve the eff i-ciency of the snow removal process, especially duringlow visibility conditions. Improved control of the snow-clearing vehicles leads to increased airport capacity.

impact of data link services on contro l l e rworkload. Other secondar y objectivesw e re developed to assist in achieving themain goal. These sub-objectives includ-ed assessments of:the subjective workload associated withRTF and data link usage;•the ef fect of data link on speech work-l o a d ;•the relative effects of each service, sin-gularly and in combination with theother data link services; and•the relative safety of the data link serv i c e s .

The gathering of controller feedbackon the data link HMI, roles and re s p o n-sibilities, and data link concepts and pro-c e d u res, were also included.

The prototype aeronautical telecom-munication network (ATN) user demon-strator and evaluation system, known asPRELUDE, was used to collect both sub-jective and objective data for all thre eN ATS EOLIA simulations. PRELUDEf o rms part of the NATS fast and re a l -time simulation capabilities located atthe Air Tr a ffic Management Develop-ment Centre in Bournemouth. Thesefacilities are used by NATS and its cus-tomers to develop and assess new AT M

tools and to evaluate, and train on, newairspace design and pro c e d u re s .

The simulation focused on the use ofdata link ser vices that off e red potentialworkload benefits through automation ofroutine “housekeeping” tasks. Thes e rvices selected included DLIC, theenabling service; ACM, the transfer ofcommunication ser vice; DSC, for thep rovision of standard arrival inform a t i o n ;and the flight plan consistency (FLIPCY)s e r vice for the automated checking ofroute inform a t i o n .

The data link equipage ratio was set at70 percent for all data link exercises (70 percent was also used by pro j e c tp a rtners in other EOLIA evaluations).

Six operationally experienced and cur-rently validated controllers took part inthe simulation. Since the PRELUDE sys-tem is a small scale re p resentation of theplanned Swanwick system, it was are q u i rement that all of the contro l l e r shad completed courses on HMI familiar-ization at the New En-Route Centre atSwanwick, and there f o re had an under-standing of the underlying platform. Aperiod of training was conducted at thebeginning of the simulation to ensurethat controllers were familiar with thedata link extensions to the HMI and theconcept of data link ser vices beforecommencing the measured exerc i s e s .

A total of 27 measured exercises wereachieved during the nine-day simulation.The design of the timetable enabled thedata link services to be simulated indi-v i d u a l l y, in pairs and in triplet. Thisa p p roach enabled the relative ef fects ofeach service and of the diff e rent combi-nations of services to be quantified. Thesimulation included measured exerc i s e s

N A LYSIS of a series of simula-tions of the data link human-

machine inter face (HMI)indicates that the implementation ofselected data link ser vices can re d u c ethe workload of the controller as well asradiotelephony (RTF) usage.

The simulations and their analysis,p e rf o rmed by the U.K. National Air Tr a f-fic S e rvices (NATS) Research and Devel-o p m e n t G roup as part of the Euro p e a nEOLIA project*, involved a team ofhuman factors specialists, software engi-neers, cost-benefit specialists, safety spe-cialists and simulation scientists.

The first of the NATS simulations tookplace in December 1998 with the purposeof obtaining initial controller feedback onthe prototype data link HMI for thre es e rvices, specifically data link initiationcapability (DLIC), air traffic control com-munications management (ACM), andair traf fic control clearances (ACL).

The second simulation, which tookplace in April 1999, focused on obtainingf u rther controller comment on theenhanced HMI and the associated datalink pro c e d u res. In addition, the down-s t ream clearance service (DSC) wasexposed to controllers for the first time.

The third simulation in this series,described in detail below, took place inJ a n u a ry 2000.

Focus on workloadThe prime objective of the third simu-

lation was to measure and assess the

D ATA LINK SIMULAT I O N S

ICAO JOURNAL10

Simulations study the impact of variousdata link services on controller workload

Simulated exercises involving data link services which are intended to automate routine tasks haverevealed that implementation of data link has a beneficial effect on controller workload. The re s u l t salso point to potential safety benefit s .

MA R K GR E E N • GA RY CO L L E D G E

NAT I O N A L AI R TR A F F I C SE RV I C E S LT D.

( UN I T E D KI N G D O M)

Maastricht London

CDA Link• ACM• ACL

DDA Link

Voice RTF

• DSC(STAR Delivery)

▲

F i g u re 1. Types of data links used in theN ATS simulations.

A

request. Prior to the simulation part i c i-pating controllers stated that they wouldaccept having such a message automati-cally generated and uplinked, there b yeliminating the need for response from ac o n t ro l l e r. Compared to the current situ-ation in the United Kingdom, where thee n t ry sector controller provides the stan-d a rd arrival route to the aircraft, the useof DSC STAR off e red the potential forless radio communication and re d u c e dc o n t roller workload.

F i g u re 1 illustrates the types of AT Nlink used in the NATS simulations. Inthis example, the aircraft in Maastricht’sairspace is in RTF contact with thea p p ropriate Maastricht sector contro l l e rand also has established a current dataauthority (CDA) link with Maastricht.ACL and ACM messages can be exchan-ged over this link. In addition, the a i rcraft has established a downstre a mlink with the London control centret h rough which it can obtain standarda rrival information prior to entering U.K.a i r s p a c e .

Air traffic control communicationsm a n a g e m e n t. The ACM service pro v i d e sautomated assistance to airc rew and con-t rollers for the transfer of ATC commu-

nications. Two versions of ACM, term e d“ p a rtial” and “full,” were used during thes i m u l a t i o n s .

P a rtial ACM is a combination of cur-rent practice together with future data linkp ro c e d u res. The airc re w, having beent r a n s f e rred by the previous sector, makean initial RTF call to the contro l l e r. Thec o n t roller acknowledges the RTF call andthe flight then pro g resses norm a l l yt h rough the sector. When the contro l l e rno longer re q u i res that the flight re m a i non the fre q u e n c y, he selects the airc r a f tand presses the “OutComm” button onthe keyboard. The flight data pro c e s s i n gsystem identifies the next sector nameand RTF frequency and automatically pre-p a res a message, known as a voice chan-nel instruction (VCI), which is uplinked.Once the airc rew has received t h i si n s t ruction, a “will comply” (WILCO) m e s-sage is sent to the transferring contro l l e r

using radiotelephony only so as to estab-lish a baseline against which the datalink exercises could be compare d .

It was ensured during developmentthat the PRELUDE system data linkHMI retained the philosophy and con-cepts of the Swanwick platform. Forexample, the colours presented are thesame, with orange used in the data linkextensions to highlight the need for con-t roller action.

Following is a brief description of datalink services involved in the simulation.

Data link initiation capability. DLIC isthe pre requisite service for exchanginga d d ress information between the air andg round systems. After an aircraft haslogged onto the ground system, the con-t roller was notified of this event by pro-vision of a data link specific symbol inthe track data block (TDB). The symbol,which appears at the left of the airc r a f tcall sign, is re f e rred to as the “data linkstatus indicator” (or “data flash” as it ism o re commonly known). The appear-ance of a grey data flash informs the con-t roller that an aircraft has logged ontothe ground system.

The other information depicted in thetrack data block includes the airc r a f t ’ scall sign, the secondar y surv e i l l a n c eradar (SSR) Mode level, the planned sec-tor level, the exit fix and the gro u n dspeed of the flight.

D o w n s t ream clearance serv i c e. TheDSC service enables airc rew to obtainclearances and information from an airt r a ffic services (ATS) unit that is fart h e ralong the route of the flight; in otherw o rds, it facilitates contact with a unitthat is not yet in control of the flight.

The establishment of a downstre a mlink is indicated to the controller bymeans of a white data flash symbol. Inaddition, notification is provided in a sta-tus list window, which shows the data linkstatus of all flights logged onto the sector.

For the purpose of the simulation,N ATS selected one specific subser v i c eof DSC, known as DSC STAR, whichentails the automatic uplink of the stan-d a rd ar rival route and active ru n w a yin response to an airc re w - g e n e r a t e d

D ATA LINK SIMULAT I O N S

11NUMBER 3, 2001

Real-time simulation facilities at the ATM Development Centre in Bournemouth,U.K. can be used for ATM demonstration, assessment, validation and training. Thefacilities incorporate an advanced recording system to capture any objective datarequired. The scale of simulation can range from a single sector to all 36 work-stations plus three unmanned support positions.

*The European pre-operational data link applications(EOLIA) project comprises a wide series of AT N -based data link development studies and trials. Thep roject, with funding from the European Commissionand Euro c o n t rol, had five main partners: NATS Ltd.;NLR, the Dutch aviation re s e a rch agency; Sofréavia;and the aerospace companies of Airsys-ATM andA e rospatiale-Matra Airbus. Airbus, British Airw a y sand Air France acted as consultants over the durationof the programme, which concluded in June 2000after a period of four and a half years.

of the SAMON waypoint. The orange “R”in the target label indicates that a ro u t ed i s c repancy exists. In addition, both theroute over the ground and the FMSroute are depicted on the contro l l e r ’ sd i s p l a y. The air route is shown in whitewhile the ground-held route is indicatedin blue.

M e a s u rements and analysesVarious measurements were taken

during the simulation and subsequentlyanalysed. They included radiotelephonyusage — thus allowing the duration andp e rcentage of time each contro l l e rspent transmitting and listening to radiomessages to be calculated.

The subjective workload of the con-t roller was determined bymeans of a tool known asinstantaneous self assessment(ISA), which re c o rds a con-t roller’s perception of thelevel of workload at re g u l a ri n t e rvals during an exerc i s e .Wi th I SA , t he c on tr o l l e rresponds every two minutesto a prompt on the display byselecting one of five buttonsthat re p resent the level of per-ceived workload, rangingf rom too little to excessive.

Analysis also focused on theimpact on the point of transfer ofcommunications. A comparisonwas made between those transfera reas w h e re aircraft were hand-ed over from one sector toanother using data l ink, andthose wher e the t r a n sfer wasaccomplished through radiotele-p h o n y. Another focal point was thenumber or severity of conflicts fol-lowing introduction of data links e rv i c e s .

The data link messages them-selves were examined to deter-mine the average response timeand evaluate how many of the mes-sages went unanswered. Thelength of time that the airc r a f twas not in communication withthe controller (i.e. the time lapse

between pressing Outcomm and I n c o m mon the keyboard) was calculated a n dc o m p a red to data f rom the RT F - o n l ye x e rc i s e s .

In addition, information was com-piled through questionnaires completedby participating controllers. One ofthese took the form of a workbookdesigned to gather opinions about thebenefits of the EOLIA ser vices and thedata link HMI and associated pro c e-d u res, as well as the safety issues. Thesecond questionnaire, the softwareusability measurement inventory, wasused to quantify c o n t roller satisfactionwith various aspects of the human-machine interf a c e .

The controllers were debriefed bothindividually and in groups. The debrief-ings considered human factors, safetyissues and benefits. Participants also hadthe opportunity to raise any pro b l e m se n c o u n t e red during the simulation exer-cises and to comment on the data linkp ro c e d u res used.

Safety issues were identified by study-ing the workbooks and compiling notesf rom the controller debriefings, with sup-p o rting data from the conflict analysis.The debriefings made it possible toe x p l o re the questionnaire responses ing reater detail.

and radio contact is established withthe next sector contro l l e r.

The full ACM ser vice extendsthis functionality furt h e r, re m o v i n gthe need for the initial RTF contact.As such, the pilot no longer makesan initial RTF call to the re c e i v i n gc o n t ro l l e r, but instead downlinks adata link message known as themonitoring RTF message (MRT ) .This message informs the con-t roller that the crew is listening fori n s t ructions on the local sectorRTF fre q u e n c y.

The receipt of an MRT messageis highlighted to the controller bythe data flash, which begins pulsat-ing in an orange colour. This HMIhighlight is removed once theflight is accepted by the contro l l e r,and the colour of the data flashchanges to green, indicating that thec o n t roller has become the current dataauthority for the flight.

Flight plan consistency. The FLIPCYs e rvice is designed to draw the con-t roller’s attention to discrepancies be-tween the route over the ground and theroute as stored in the aircraft’s flightmanagement system (FMS).

Once a discrepancy is detected, it isp resented to the planner and then thetactical controllers. F i g u re 2 is re p re s e n-tative of the display seen by the tacticalc o n t roller should a discrepancy in theroutes still exist when the aircraft entersthe sector. The aircraft with the ro u t ed i s c repancy in this example, Delta 77,has entered Sector 11 and is in the vicinity

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ICAO JOURNAL12

F i g u re 2. Example of a discrepancy display. In this case, theorange "R" informs the controller that there is a discre p-ancy between the planned routing held by the local AT Csystem and the airc r a f t ’s intentions. Both planner andtactical controllers are alerted to such discrepancies ata p p ropriate stages of the fli g h t .

Figure 3. Bars show impact of different data linkservices and combinations of services on RT Fusage in Sector 11 (left) and Sector 10.

Baseline A D F AD AF DF ADF ADF0

10

20

30

When the data link services were sim-ulated individually, FLIPCY produced aworkload reduction, while the individualimpact of the ACM and DSC services onc o n t roller workload was negligible.

In addition to analysis of workload rat-ings provided by the controllers duringthe exercises, workload-re l a t e dquestions in the workbooks showedthat the participating contro l l e r sbelieved the use of data link in thesimulation was largely beneficial int e rms of workload. However, addi-tional workload did accrue from thevisual scanning needed to locatedata link equipped aircraft on the sit-uation display. Work was also gener-ated by some additional interf a c etasks re q u i red for data link use. Thec o n t rollers believed that the effi-ciency of the human-machine inter-face would be important in futuresystems incorporating data link.

The majority of the participating con-t rollers did not believe that the data links e rvices that had been simulated had animpact on the pace at which they carr i e dout their tasks.

All of the participants indicated thatuse of the fully automated DSC STA Rs e rvice resulted in fewer repetitive taskswhen compared to the RTF enviro n-ment. This was because the contro l l e r sdid not have to provide airc rew with thes t a n d a rd arrival routes, as this inform a-tion was relayed to the crew by the DSCs e rvice before the aircraft entered U.K.airspace. The controllers stated thatthey would want the provision of stan-d a rd arrival route information to be fullya u t o m a t e d .

F i g u re 4 shows how the contro l l e r srated the individual services in terms oftheir operational benefit. The dotted h o r-izontal red line shows the point abovewhich services are considere d to havean operational benefit. As can be seen,the controllers rated the automated DSCS TAR service as having the gre a t e s toperational benefit. The only service tofall below the red line was partial ACM,although controllers rated this service ashaving specific safety benefits.

Safety benefits and issuesThe controllers stated that the simula-

tion of data link services showed there isthe potential to enhance safety, especiallyby reducing the risk of an airc rew takingthe wrong call or misunderstanding amessage. No conflicts or losses of separa-

tion were attributed to the use of data link.A majority of participants believed

that the data link services in generalwould reduce errors by of fering the abil-ity to uniquely address a specific flight.

The ACM service was singled out aso ffering a significant safety benefit as ito ff e red the potential to eliminate thesending and receiving of incorrect RT Ff requencies, a possibility that has in-c reased with the introduction of six-digitf requencies. As aircraft would be unique-ly addressed, the problem of the wro n gc rew taking the call and leaving the fre-quency pre m a t u rely would be re s o l v e d .The controllers stated that they liked thec o n fidence gained by initial voice contact,and recommended that the “voice in”

General findingsThe first of the findings concern e d

RTF workload. As one would expect, thenumber of RTF messages and the timespent communicating via radiotelephonydeclined with the introduction of datalink serv i c e s .

Although the introduction of data links e rvices generally saw a reduction inR TF workload, there was a s ingleinstance when the use of radiotelephonyi n c reased. However, the increase associ-ated with the use of the DSC serv i c ea p p e a red to be spurious and pro b a b l yresulted from a diff e rent style of contro l-ling by one of the participants. Thei n c rease in RTF workload for this exer-cise is not believed to be related to thei n t roduction of the DSC serv i c e .

As a general indication of RTF usage,statistics were gathered from all 27m e a s u red exercises. The mean timespent using radiotelephony during all ofthe exercises, averaged across both sec-tors, was calculated as 21 percent. Theaverage duration of an RTF messagewas between three to four seconds.

The reduction in RTF usage wasg reater as more services were added(F i g u re 3). The DSC and FLIPCY serv i-ces were only applicable for Sector 11, the FIR entry sector. Changes in RT Floading for Sector 10 during DSC andFLIPCY exercises were due to the vari-ability of results and dif f e rent styles ofc o n t ro l l i n g .

The reduction in RTF usage experi-enced in the exercises in which all of thedata link services were used can also beseen in Figure 3.

C o n t roller workloadThe scores collected during the series

of exercises indicates that contro l l e rworkload would benefit from the intro-duction of data link services. A gre a t e rreduction in controller workload wasachieved by using a combination of datalink ser vices rather than any one serv-ice. Further studies will be re q u i red tod e t e rmine which combinations of datalink services are likely to provide theoptimum controller workload benefit.

D ATA L INK SIMULAT I O N S

13NUMBER 3, 2001

At the time the work described in this article was inprogress, Mark Green was an ATC Systems Specialistand Gary Colledge was a Technical Group Leader in theResearch and Development Group of National AirTr a ffic Services Ltd. Mr. Green is now an ATC Planner inTerminal Control Projects, and Mr. Colledge is an AT MExpert-Datalinks in the Department of ATM Policy andP e r f o r m a n c e .

This article is an adaptation of a presentation madeby the authors at the ATN 2000 Conference inSeptember 2000 at the Institute of Electrical Engineers(IEE), London. Further information about this and otherN ATS simulations can be obtained from the simulationproject manager, Cheryl Kilner, at the Air Tr a ff i cManagement Development Centre in Bournemouth.

continued on page 42

FLIPCY DSC STAR DSC STAR ACM ACM0

1

2

3

4

(Semi-automatic) (Fully-automatic) (Partial) (Full)

Figure 4. Controller perception of the opera-tional benefit associated with individual datalink services.

3.673.33

4.20

2.803.25

with the aviation world, is not the onlyunusual aspect of this safety initiative.Capstone is unique in both how it start-ed and what it set out to achieve.

Understanding Capstone re q u i re ss o m e b a c k g round on Alaska. Among the50 states comprising the United States,Alaska is the largest in area, but withonly 600,000 people it is one of the small-est in population. One out of every 58people in the state is a pilot, and therea re six aeroplanes for every 10 pilots.While aviation has emerged as Alaska’smost important transportation system,h o w e v e r, the vital infrastru c t u re sup-p o rting this essential system falls shortof the standards commonly expected orfound elsewhere .

The Yukon-Kuskokwim Delta area ofs o u t h - w e s t e rn Alaska, the focal point forCapstone’s initial activities, typifies mostof the state in terms of transport a t i o ni n f r a s t ru c t u re. There are no roads con-necting the more than 50 villages in the1 0 0 , 0 0 0 - s q u a re-mile area, and even with-in the villages themselves there are fewroads. The community of Bethel, the avi-ation operating hub and largest settle-ment in the area, has only 15 miles ofmostly unpaved roads — all ending atthe edge of town.

Many of the villages of the region arewithout cars. During winter, when thetundra is frozen, personal t r a n s p o rt a t i o nfor short distances isby snowmobile or dogsled. During summerthe tundra conditionslimit travel to all-terr a i nv e h icles within the vil-lage itself. The majormode of transport a t i o nbetween the villages

and the rest of the state is air transport ,meaning that the villages depend on avi-ation for all of their essentials.

Despite the importance of aviation toAlaskan communities, runways are oftens h o rt, narro w, made of gravel, unlightedand without weather re p o rting systemsor instrument approach capability. ManyAlaskan communities are served only bysmall single-engine aircraft which areusually limited to daytime visual flightrules (VFR) operations.

This environment has made Alaskastand out in terms of the number of air-craft accidents and fatalities. On averaget h e re is an accident-related fatality everynine days. More than one third of theannual air commuter accidents of theUnited States occur in Alaska, and morethan 10 percent of the professional pilotsworking there do not survive a 30-yearc a reer (F i g u re 1). More o v e r, they sel-dom die alone.

It is the lack of useable instru m e n tflight rules (IFR) infrastru c t u re or radarcoverage, combined with the harshweather conditions, that causes Alaska tohave such a high rate of CFIT accidents.Pilots, departing for VFR-only destina-tions with the intention of maintainingvisual separation from the terrain, c o n-tinue t o w a rds their destination aftere n c o u n t e r i n g m a rginal weather thatwould normally call for IFR operations.

HE harsh operating enviro n-ment of Alaska contributes to anaverage of one aircraft accident

e v e ry other day. To combat this unusual-ly severe accident rate, a safety initiativethat makes use of advanced technologiesto enhance situational awareness is nowunder way. A “real world” evaluation ofthe ef fectiveness of these new techno-logies in improving safety, as well as p roducing other benefits, was initiated inJ a n u a ry 2001.

An avionics package comprised ofmany of the same systems envisaged forglobal communications, navigation, sur-veillance and air traf fic management( C N S / ATM) is at the heart of the A l a s-kan initiative, known as the Capstonep rogramme. The bundle of avionics isc u rrently being installed on some 150a i rcraft used for commuter, charter andmail flights in an area of south-west Alaska with the primary goal of pre v e n t-ing controlled flight into terrain (CFIT)a c c i d e n t s .

Need for actionA geologic “capstone” is a large ro c k

or other object of mass pressing downon, and thereby stabilizing, a foundationof otherwise loose material. This namewas chosen for the Alaskan initiativebecause of the re q u i rement to holdtogether and stabilize loosely re l a t e dtechnologies and programmes in muchthe same way a capstone holds togetherloose material. The name, at first seem-ing to have more to do with geology than

SAF ETY PROGRAMME

Innovative safety initiative in Alaskaputs spotlight on advanced technologies

A fleet of small aircraft is being equipped for a “real world” evaluation of the safety benefits arisingf rom the use of advanced technologies in Alaska’s high-risk operating enviro n m e n t .

JO H N HA L L I N A N • JA M E S CA L L

FE D E R A L AV I AT I O N AD M I N I S T R AT I O N

( UN I T E D STAT E S)

15NUMBER 3, 2001

All accidents All fatal accidents

37%Alaska

21%Alaska79%

U.S. States(except Alaska)

63%U.S. States(except Alaska)

F i g u re 1. Commuter and air taxi accidents in the United Statesand in Alaska, 1990-98.

T

Tackling the pro b l e mN u m e rous studies have long addre s-

sed Alaska’s aviation needs, but actualchange has occurred at a painfully slowpace. Capstone is changing that; in 1998it sparked the beginning of a part n e r s h i pbetween the U.S. Federal Aviation Ad-ministration (FAA) and the state’s avia-tion community in tackling the safetyissue. Aviation leaders agreed that get-ting something accomplished re q u i re dtaking action rather than simply study-ing the pro b l e m .

Highlighted in these aviation studieswas the role that new and emerg i n gtechnologies might play in ef fecting asafety improvement. But most tech-

nology demons t r a t i o n sfoc us on a “ p roof of concept,” and are there-f o re carefully orc h e s t r a t e dl a b o r a t o r y or academice x e rcises involving a lim-ited number of airc r a f tand specifically trainedflight crews. In the eff o r tto prove or disprove aconcept, strict adhere n c eto carefully scripted flightp rofiles e n s u res dataa c c u r a c y, f ree of unac-counted for variables orintangible elements. Such

assessments fall short of measuringthe “bottom line” impact in re a l -world operations. Safety managershave long known that the actualbottom line for safety includes thevariable and intangible elementse n c o u n t e red daily in the re a le n v i ro n m e n t .

Phase I of the Capstone initiativeinvolves up to 150 commercial air-c r a f t based in the Yu k o n - K u s k o k-w i m Delta that are being equipped,on a voluntary basis, with govern-m e n t - f u rnished avionics. Serv i c e sp rovided via the advanced avionicswill improve pilots’ flight capabili-ties and situational awareness. Par-ticipating aircraft receive an IFR-

c e rtified GPS navigation re c e i v e r,ADS-B transmitter and re c e i v e r, and

a multi-function colour display (MFD).The MFD has a moving map displayfunction with terrain advisory capabilityand displays broadcasted weather infor-m a t i o n .

A network of data link ground stationsa re being installed at up to 12 existingFAA and joint-use facilities in the re g i o n ,connected via existing communicationssystems to FAA air traffic control (AT C )facilities. The existing automated radartracking system (Micro - E A RTS) at theAnchorage area control centre (ACC)has been programmed to depict ADS-Bt a rgets, fused with radar targets, on theair traf fic controller displays (F i g u re 2) .ADS-B aircraft position re p o rts will alsobe made available to operators for flightfollowing purposes.

As part of the Capstone initiative, FA Ahas undertaken to purchase, install andmaintain the avionics on part i c i p a t i n ga i rcraft for the evaluation period. Inre t u rn, aircraft operators assist the pro-gramme by providing evaluation data sothat safety and operational benefits canbe identified and documented.

Installation of the equipment began inDecember 1999 following a pro o f - o f - c o n-cept demonstration earlier in the year.The evaluation began in January 2000,and concentrated initially on pro v i d i n gan aff o rdable means to reduce CFIT,

Enhanced situational aware n e s scan improve the safety of suchoperations. The Capstone avionicspackage, which includes an intu-itive, high-resolution colour displaythat re p resents terrain in fourcolours (black, green, yellow andred) indicating the proximity to thea i rcraft, is intended to provide thisa w a reness. The avionics continu-ously monitors the aircraft’s alti-tude, its global positioning system(GPS) derived position, gro u n dspeed and flight route, and com-p a res this to a built-in database oft e rrain elevation. The display auto-matically provides a terrain advi-s o r y if the aircraft is within twominutes of a close encounter withthe gro u n d .

Second in number to CFIT accidentsis mid-air collisions. Capstone seeks tochange this by employing automatic de-pendent surv e i l l a n c e - b roadcast (ADS-B)t e c h n o l o g y. ADS-B equipped airc r a f tb roadcast their position whether theya re flying or taxiing on the airport sur-face. Using the multifunction display,ADS-B gives pilots in the cockpit a clearview of traffic around them. Addition-a l l y, ADS-B receivers on the ground canrelay aircraft position information in real time to airport ground contro l l e r s,a p p roach controllers and en-route con-t rollers. This low-cost solution can p rovide radar-like surveillance whereradar is not feasible.

SAFETY PROGRAMME

ICAO JOURNAL16

F i g u re 2. Radar contro l l e r ’s display at Anchorage ACCf e a t u res radar and ADS-B targets.

F i g u re 3. Capstone programme data link arc h i t e c t u re.

n e a r - t e rm safety benefits and pro d u c edata for validation of the overall benefitsexpected from modernization. In somecases, the targeted technologies (e.g.AWOS) were already well established,but under-utilized. In other cases, such aswith ADS-B and aff o rdable CFIT avoid-ance capability, Capstone has engaged ins i g n i ficant developmental activities.

Fielding a bundle of avionics in a re a l-istic validation ef f o rt offers multiple ben-efits. First, the improvements can yieldimmediate safety benefits. Second, theresulting infrastru c t u re permits initialp ro c e d u res development while familiar-izing flight crews andc o n t rollers with modernequipment and concepts.T h i rd, this infrastru c t u redevelopment also accel-erates the identificationand resolution of cert i fi-cation issues and perm i t sv a l idation of numero u sp reviously i d e n t i fied con-c e p t s, such as the use ofADS-B in lieu of radar in non-radar airspace.F i n a l l y, real-world valida-tion permits the disco-v e r y and assessment ofmany o t h e rwise intan-gible elements, i n c l u d-ing issues of flight crew acceptanceand operator reliance, display sym-b o l o g y, air traf fic controller accepta n c e ,interaction of “bundled” technologies,and so fort h .

Since real-world validation can onlytake place in a normal day-to-day envi-ronment, reliable results are possibleonly if there is participation by enougha i rcraft and flight crews over a longenough period. The validation mustinvolve a variety of aircraft types, pilotshaving a wide range of knowledge, skilland ability, and combinations of weatherand other environmental extre m e s .

Key element is ADS-BThe natural boundaries of the Yu k o n -

Kuskokwim Delta confine the operationof most of the locally based aircraft to

the area, with Bethel as the hub, andalso limit radar coverage below 6,000 feetmean sea level (MSL). Capstone will pro-vide an IFR infrastru c t u re for Bethel andbeyond to nine additional airports in theYukon/Kuskokwim Delta, making radar-like ADS-B coverage possible thro u g h-out this are a .

To document the results, Capstonehas enlisted the help of the University ofAlaska at Anchorage (UAA). The univer-sity will document a baseline of curre n toperations and will track, evaluate anddocument the improvements as theyo c c u r. UAA will also provide flight cre w

training in Capstone’s technologies.A key element in the Capstone pro-

gramme that may eventually change the face of aviation worldwide is ADS-B.Although some concepts envisage ab road ADS-B deployment in support off u t u re ATM systems, no long-term deci-sion on ADS-B data link technology hasyet been made by the United States.C u rre n t l y, three data-link systems —Mode S, VDL Mode 4 and universalaccess transceiver (UAT) — are underconsideration for the U.S. national air-space system (NAS).

A data link decision expected laterthis year may provide for one or more ofthe three systems. Instead of waiting onthis decision, however, the aviation com-munity in Alaska decided that the safetybenefits from early deployment of an

enhance capability to see and avoid near-by traffic, and relay weather inform a t i o nto the cockpit. Additional enhancementswill be evaluated as part of the Capstoneinitiative through 2002. The pro g r a m m ealso provides special training for thepilots, operators, safety inspectors, AT Cspecialists, and technicians involved toe n s u re that the evaluation will generatethe maximum benefits. At the end of theevaluation, avionics equipment will bereclaimed or left with participants ina c c o rdance with agreements and gov-e rnment re g u l a t i o n s .

In order to support the most eff e c t i v euse of this technology, 19 stand-aloneGPS non-precision instrument appro a c hp ro c e d u res are being pre p a red and pub-lished for one or more runways at 10remote village airports within the evalu-ation area. Also, automated weathero b s e r vation systems (AWOS) will beinstalled at these airports to support airc a rrier use of the new non-precision GPSi n s t rument approach pro c e d u re s .

The AWOS is a suite of sensors whichm e a s u res, collects and disseminatesweather data to help meteoro l o g i s t s ,pilots and flight dispatchers pre p a re andmonitor weather forecasts, plan flightroutes, and provide necessary inform a-tion for take-offs and landings. AW O Sp rovides minute-to-minute updates topilots by a ver y high frequency (VHF)radio on a frequency between 118 and136 megahertz (MHz) or via telephone.AWOS III measures wind direction andspeed (including gusts), temperature ,dew point, altimeter setting, density alti-tude, visibility, and cloud amount, heightand type.

Real-world validationA real-world validation involves field-

ing multiple safety-enhancing tech-n ologies in such a manner that theire f fectiveness can be assessed. Thisre q u i res stepping immediately from ap roof-of-concept stage through cert i f i c a-tion to suf ficient system-wide equipage.Capstone, there f o re, brings together themost promising new and emerging tech-nologies into a programme to leverage

SAFETY PROGRAMME

17NUMBER 3, 2001

Figure 4. An aircraft fitted with avionics used in theCapstone programme. Some 150 aircraft are expected tobe equipped by mid-2001.

radar airspace, including use in IFR conditions. Early last year the FAA re s-ponded favourably to this request pro-vided that ADS-B could be shown to beat least as accurate and reliable as r a d a r. This triggered sev-eral activities, includingdevelopment of a draft min-imum operational perf o rm-ance standards (MOPS)document for the UATsystem and certification tothat new standard. Initialsystem testing was con-ducted at the FAA Wi l l i a mJ. Hughes Technical Center in New Jerseyin May 2000, followed a few monthslater by flight testing of the entire sys-tem in Bethel (F i g u re 5). Additional data were collected and analysed over a 30-day period to further ensure accuracyand end-to-end system re l i a b i l i t y.

P ro c e d u res were developed for theuse of ADS-B by both ATC and the flightc rews. Generally, the ADS-B pro c e d u re s

used in the Capstone pro g r a m m ea re identical to radar pro c e d u re s .Instead of being issued a discre t efour-digit transponder “beaconcode” by ATC, when fitted withADS-B each aircraft transmits itsown permanent airframe addre s s .This permanent address is pro-grammed into an aircraft’s UATsystem during installation. TheU AT design also includes a privacymode which transmits a randomlygenerated address for each flightrather than the aircraft specifica d d ress. This provides the f u n c-tional equivalent of a 1200 t r a n s-p o n d e r code with a tradi tionalradar system. Pilots desiring AT C

s e rvice must ensure their equipment istransmitting the aircraft-specific addre s sprior to contacting AT C .

The last item to be accomplished wasto move the Capstone system from itsoriginally assigned spectrum at 966 MHzto a “protected” spectrum at 981 MHz.This involves replacing cards in each ofthe equipped aircraft, a process thatbegan in January 2001. Only airc r a f t

operating on 981 MHz are able toreceive the radar-like ATC serv i c e .

All of these eff o r ts culminated, on 1 January 2001, in the use of ADS-B tosequence and separate aircraft, the first

time in over half a centurythat a new air traf fic toolwas introduced for sur-veillance in the UnitedStates. After a year of datagathering and testing, theFAA and its industry part-ners initiated the first useof ADS-B technology totrack and service traffic in

a reas that have no radar coverage. On 31 December 2000, while most Alaskansw e re preparing to ring in the New Ye a r,Alaskan region airway facilities special-ists enabled the Anchorage ACC dis-plays to receive ADS-B surv e i l l a n c ei n f o rmation from the airspace aro u n dBethel. At 15:18 local time (00:18 UTCon 1 January 2001), a Yute Air C-212 andN o rt h e rn Air Cargo DC-6 cargo flightbecame the first passenger and carg oflights respectively to receive vectorsbased on ADS-B. This radar-like serv i c econtinues in use today at Bethel.

Next stepsThe equipment installed in Capstone

a i rcraft, although fully certified, re m a i n sg o v e rnment owned and private copiesa re not available for sale. Although thebenefits of ADS-B for air-to-air and air-t o - g round applications are intuitively obvious, the data link portion of thisequipment remains out of reach of pri-v a t e individuals pending the planned datalink and long-term spectrum decisions.

Radio frequency spectrum is muchlike real estate in that someone or otherhas staked a claim to every bit of it and none is left for homesteading. For m o d e rnization to actually take place,

ADS-B system far outweighed the riskassociated with delay. Thus, Capstonepublished its re q u i rements in Marc h1999 and, following the proof- of-conceptdemonstration, accepted a proposal byUPS Aviation Technologies. This pro-posal, based on the MITRE Corp. UATdesign, was chosen in light of the systemcapability and overall cost. Capstone’soverall ADS-B arc h i t e c t u re is shown inF i g u re 3.

UPS Aviation Technologies designedthe ground broadcast transceiver (GBT)used to transmit aircraft position infor-mation to the Anchorage ACC automatedradar tracking system. For an ADS-Bequipped aircraft, each ground bro a d-cast transceiver enables the functionalequivalent of radar-like surveillance forabout one-fiftieth of the cost.

Following completion of cert i f i c a t i o nactivities in Januar y 2000, airc r a f tequipage commenced. At the time ofwriting (January 2001), a fleet of over 75 aircraft operate in commercial serv i c e

e v e ry day in the Yu k o n / K u s k o k w i mDelta using ADS-B as an enhancementto VFR situational awareness. It wasanticipated that the entire fleet of 150 air-craft will have been equipped for thiscapability by mid-2001 (F i g u re 4) .

Recognizing the potential benefits, the aviation community requested that ADS-B be approved for use by ATC inp roviding sur veillance ser vices in non-

SAFETY PROGRAMME

ICAO JOURNAL18

John Hallinan, the Capstone Programme Manager, isbased in Anchorage, Alaska at the Capstone ProgrammeO ffice. James Call is the Flight Standards OperationsSpecialist coordinating data collection and analysis andfuture Capstone plans for the next demonstration insouth-east Alaska.

For further information about the Capstone programme,visit the FAA website (www. a l a s k a . f a a . g o v / c a p s t o n e ) .

continued on page 42

key element of

Capstone that

may change the face

of aviation worldwide

is ADS-B

A

F i g u re 5. Comparison of ADS-B reports and radarre t u rns typical of results of tests conducted invicinity of Bethel, Alaska in summer 2000.

and operational challenges, but alsonational and political matters of a deli-cate and often complex nature . ”

The opening of the four polar airroutes to commercial air traffic on 1F e b ru a ry 2001 was preceded by morethan 450 airline demonstration flightsdating back to 1998. The new ro u t e sa ff o rd significant economic benefits toairlines and their passengers.

The first initiative aimed at developingthe polar air routes was taken in the fallof 1997 with the decision to create ahigh-level steering group to coord i n a t ethe ef f o rt. The ICAO Informal Tr a n s -A s i a / Tr a n s - S i b e r i a / C ross-Polar RoutesHigh Level Steering Group (ITA S P S ) ,c h a i red by Dr. Kotaite, is made up of o f ficials from Canada, China, Finland,G e rm a n y, Iceland, Japan, Mongolia,N o rw a y, the Russian Federation and theUnited States. IATA, which is also amember of the group, re p resents the air-

lines concern e d .The polar routes developed by

I TASPS link North America andE u rope with Asia through the air-spaces of Canada, China, Iceland,Mongolia, the Russian Federationand the United States, and formone of six air traffic services (AT S )transit route systems thro u g hRussian airspace.

In a parallel and complementa-ry initiative, Nav Canada and theFederal Aviation Authority ofRussia (FAAR) jointly conducteda polar routes feasibility study,published in August 2000, whichlooked at many factors including:• t r a f fic levels between Nor t hAmerica and Asia;•wind patter ns af fecting the

polar re g i o n ;•the demand and capacity of the pro-posed ro u t e s ;•operational and technical re q u i re m e n t s ;•costs, revenues, economic ef f i c i e n c yand other financial data; and •airline and passenger benefits.

The objective of the joint study was tod e t e rmine whether a business case couldbe made for opening and operating fourATS routes identified as Polar Routes 1,2, 3 and 4 by assessing the viability ofpolar routes between North America andAsia, as well as the economic and techni-cal impact on the Russian Federation andCanada, whose airspace the routes, inp a rt, traverse. The feasibility study alsoweighed the impact of the new routes onthe airline industry.

The study came to the conclusion thatimplementation of polar routes was bothfeasible and desirable. Following is abrief description of the key elements ofthe study.

City-pair analysis. The feasibility studyidentified 33 potential city pairs thatcould benefit from implementation ofpolar routes. Statistics were compiled tod e t e rmine the actual number of passen-gers that travelled between the selectedcities with distances greater than 6,600nautical miles, during a one-year period.

Wind analysis. An extensive windanalysis was perf o rmed for each of the33 city pairs. The study examined fuelre q u i rements, airports, wind and tem-p e r a t u re for each month of the yearbased on 10 years of weather observ a-tions supplied by the U.S. Navy and theU.S. Weather Service. Twenty-four mini-mum time tracks were produced fro mthese data, one per month from Nort hAmerica to Asia, and one from Asia to

DIRECT polar air routes thats h o rten distances between citiesin North America, Europe and

Asia recently became operational follow-ing a series of high-level meetingsbetween re p resentatives of several coun-tries, ICAO and the International AirTr a n s p o rt Association (IATA). The gro u pa g reed in late January to open a new airroute stru c t u re over the North Pole (see“New polar air routes to reduce flighttimes,” Issue No. 1/2001, page 32).

The milestone agreement was madepossible by a remarkable spirit of coop-eration. As ICAO Council President D r. Assad Kotaite stated following themeeting in Paris on 24 Januar y, theStates involved had made considerablee ff o rt to address “not only the technical

POLAR AIR ROUTES

ICAO JOURNAL20

New air route structure over North Pole off e r smajor reduction in flight times, costs

The opening of four polar routes in Febru a ry 2001, after a successful demonstration period in which more than 450 airline flights were made, promises some significant economic benefit s .

DO N MA CKE I G A N

N AV CANADA

N av Canada has taken another major step towardestablishing fully functioning polar air routes bytracking an aircraft from the Canadian - U. S. borderto 84 degr ees north, and then again in Russian air-space. Nav Canada engineers used leading - edgetechnology to monitor the first dir ect, non - stopservice betw een Newark and Hong Kong on 1 March 2001.

The flight, operated by Continental A irlines asC OA99, follow ed Polar Route 2, which comes with-in 64 nautical miles of the North Pole. The trackingin the far north was made possible by advancedtechnology curr ently being tested for introductioninto the transatlantic and northern airspace airtraffic control (ATC) systems. Implementation ofthis technology will allow significant improvementsin safety and service for non - radar environments.

N ew technology used to trackflight over the pole

Continued on page 41

included gradual implementation of newtechnologies in the Russian area contro lc e n t res (ACCs) that provide air traff i cs e rvices to polar route traffic. Thiswould ensure that modernization, alongwith construction work and the trainingof personnel, would coincide with the

g rowth in traffic demand and with there q u i rement for additional route capaci-t y. These technologies include the globalnavigation satellite system (GNSS), auto-matic dependent sur veillance (ADS),CPDLC, ATS interfacility data communi-cation (AIDC), flight data pro c e s s i n gand new radar systems.

Economics of polar routes. A detailedeconomic analysis was perf o rmed forthe Russian and Canadian portions ofthe polar routes. This included the cal-culation of associated costs — includingcapital, operating and maintenance costs— for the Russian Federation and Nav

Canada, the Canadian air navigations e rvices (ANS) pro v i d e r. It also includedan assessment of the potential re v e n u e ,taking account of the loss of re v e n u e sthat could occur because of the re -routing of some traffic away from AT Stransit routes across the far east re g i o n

of the Russian Federation. By way ofexample, traffic from Chicago to HongKong will likely shift from the trans-e a s t e rn routes to the polar routes to takeadvantage of more favourable winds.

Aviation user benefits. The polar ro u t e sallow new non-stop flights between Nort hAmerica and Asia that reduce both traveltime and airline costs, in part through ad e c rease in the distance flown and the

N o rth America for each city pair, basedon Boeing 747-400 data.

Demand assessment. An assessment ofc u rrent and potential traf fic was madefor each city pair. Flight movementequivalent (FME) units were created toequal 275 passengers or 150,000 poundsof cargo. All of the collected data, pas-senger and cargo movements for a yearbetween selected city pairs were con-v e rted into FME units. Using the mini-mum time track information, traffic fro meach city pair was allocated to one of thefour polar routes, to the Russian trans-e a s t e rn routes (A218-B337 and G583) orto other routes, such as the Nort hPacific (NOPAC) route system. Fro mthis information, scenarios were devel-oped to predict the traffic demand on thepolar route system.

Operational assessment. The opera-tional concept for the four polar ro u t e swas based on the demand analysis and af o recast of 5 percent traf fic growth pery e a r. It was expected that traffic wouldbuild gradually and that route capacitywould be increased to meet this demand.The study introduced a phased appro a c hto air traffic management (ATM) im-p rovements that would be necessar y toaccommodate anticipated traf fic. Thefirst phase, involving services re q u i re dfor airline demonstration flights, was com-p l e t e d on 31 January 2001. In the secondphase, under way since 1 Febru a ry, re g-ular flights are supported by the existingATM system, with technical impro v e-ments under development to meet thef o recast traf fic demand. The next phasewill see certain enhancements to theRussian air traffic control (ATC) system,including the introduction of contro l l e r -p i lot data link communications (CPDLC),which may be phased in over severalyears. Later phases will intro d u c eadvanced communications, navigation,s u rveillance (CNS) and air traf fic man-agement in limited parts of the airspace,followed by the full implementation ofC N S / ATM technologies within theRussian airspace concern e d .

Technical concept. A compre h e n s i v etechnical concept was developed that

POLA R AIR ROUTES

21NUMBER 3, 2001

Communications and surveillance cover-age over northern Canada. Using newt e c h n o l o g y, Nav Canada recently moni-t o red the pro g ress of a flight as far northas 84 degre e s .

that polar routes implementation is notonly feasible but desirable. The demandfor the service exists, the operationaland technical concepts for support i n gthe safe and efficient management ofpolar traffic have been developed, andthe project is economically viable.

Operations on the polar routes is inmany ways similar to en-route oceanicoperations with respect to the availabilityof suitable alternate and emerg e n c ylanding airpor ts. There are suf f i c i e n tsuitable airports in the nort h e rn andpolar areas to meet the re q u i rements forextended range operations by twin-engined aeroplanes (ETOPS) altern a t e swithin 180 minutes from any point along

the route of the flight on the polarroutes. These airports are located in n o r-t h e rn Canada, Denmark (Gre e n l a n d ) ,the Russian Federation and Norw a y.

The opening of the four polar ro u t e sfor operational use will see an increase int r a ffic over that experienced during thedemonstration phase, with the majority ofthe flights from North America to Asiausing Polar Routes 3 and 4. While thedemonstration flights were conducted forthe most part by Boeing 747-400s serv i n gChicago–Hong Kong and Detro i t - B e i j i n g ,since 1 March 2001 the Boeing 777 hasbeen used on extended range operationsby twin-engined aeroplanes (ETOPS)between Newark and Hong Kong.

G e n e r a l l y, head winds are not a factorin the polar region, and together withs h o rter distances result in reduced fli g h ttimes from North America to Asia.C o n v e r s e l y, there are no tail winds in thea rea, so traf fic from Asia to Nort hAmerica, for the most part, continues touse the Pacific routes to take advantageof the prevailing westerly winds.

Polar flights operating through Cana-dian, Icelandic and U.S. controlled air-space can specify user-pre f e rred pro f i l e son their flight plans, and can choosef rom one of the four polar routes on theday of operation as well as route seg-ments through Russian, Chinese andMongolian airspace.

In addition to the emphasis on thepolar areas, the entry and exit points andthe associated route stru c t u re linkingthe southern segments of the polarroutes in Russia to Mongolia and Chinaalso forms a critical part of the system.As part of the ongoing eff o rt to meetf o recast demand, China, Mongolia andthe Russian Federation are looking atways to more fully utilize the segmentsof the polar routes in their re s p e c t i v eflight information regions (FIRs), withs u p p o rt from ICAO and IATA .

A i r - g round communications on thepolar routes, when outside of very high

elimination of stop-overs at locationssuch as Tokyo, Anchorage, London andF r a n k f u rt. The following examples showthe estimated time savings using polarroutes compared to today’s routes viathe North Atlantic or Pacific, for six ofthe 33 city pairs for which a wind analysiswas carried out:•Atlanta-Seoul, 124 minutes;•Boston-Hong Kong, 138 minutes;•Los Angeles-Bangkok, 142 minutes;•New Yo r k - S i n g a p o re, 209 minutes;• Vancouver-Beijing, 108 minutes; and• Vancouver-Hong Kong, 125 minutes.

On the basis of the various findings,the State Civil Aviation Authority ofRussia (SCAA) and Nav Canada agre e d

POLAR AIR ROUTES

ICAO JOURNAL22

Don MacKeigan is the Senior Advisor ATS, Domesticand Oceanic Operations at Nav Canada headquarters,Ottawa. Mr. MacKeigan was a member of the Canadiandelegation to the ITASPS High Level Steering Group.

continued on page 39

China, Mongolia and the Russian Federation are currently looking at ways to more fullyutilize the segments of the polar routes in their respective flight information re g i o n s .

dation that English be used whenevern e c e s s a ry.

“Pending the development and adop-tion of a more suitable form of speechfor universal use in aeronautical radio-telephony communications,” the annexstates, “the English language should beused as such and should be available, onrequest from any aircraft ... at all stationson the ground serving designated air-p o rts and routes used by intern a t i o n a lair services.” In the years since ICAOestablished the provisions for languageuse in the early 1950s, however, littlep ro g ress has been made in the develop-ment of a more suitable form of speech.

Fifty years on — and faced with enor-mous growth in international air travel —

the aviation communityre q u i res more stringentp rovisions for the com-mon use of the Englishlanguage in intern a t i o n a lradiotelephony commu-nications. Evidence fro mseveral incidents andaccidents highlightst h e c o n t r i b u t o r y role of communication mis-takes. With safety inmind, the 32n d I C A OAssembly held in 1998u rged that the matterbe given priority. Theresolution it a d o p t e d

called for the relevant provisions in ICAOAnnex 1, Personnel Licensing, and inICAO Annex 10, A e ronautical Te l e c o m -m u n i c a t i o n s, to be strengthened. Con-tracting States would have an obligationto take steps to ensure that air traffic con-t rol (ATC) personnel and flight cre w s

involved in operations where English is re q u i red are proficient in perf o rm i n gradiotelephony communications inEnglish (see “Safety issues related to lan-guage use have come under scru t i n y, ”Issue 2/2001, page 15).

Even before the 32n d ICAO Assemblyresolved that the language issue shouldbe given high priority, an ef f o r t wasunder way to develop provisions for s t a n d a rdized English-language testingre q u i rements and pro c e d u res, and mini-mum skill level re q u i rements in the com-mon usage of the English language. Soonafter the 1998 Assembly concluded, theICAO Air Navigation Commission (ANC)established a group of experts, known asthe Proficiency Requirements in Com-mon English (PRICE) Study Group, toassist the ICAO Secretariat in accom-plishing this task.

The original task defined in the 1950s— to develop and adopt “a more suitablef o rm of speech for universal use in aero-nautical radiotelephony communication”— has proved elusive. It is a testament tothe unique qualities of language that dur-ing the half century since adoption of the original provisions in support of acommon aviation language no furt h e rp ro g ress on development of a more suit-able form of speech has been made.

To understand why this is the case, itis important to understand the nature oflanguages. Even the best and mostthoughtful linguists do not agree pre-cisely on the nature of human language,on how humans first developed thecapacity for language, or how childre na c q u i re a first, and adults a second, lan-guage. Knowing a language means re c-ognizing the concrete thing or abstract

HOSE involved in setting inter-national standards re c o g n i z e df rom early on that a common lan-

guage for radiotelephony communica-tions was needed in the interests ofsafety and eff i c i e n c y. Within aviation,English has become firmly entre n c h e das the de-facto common language ofi n t e rnational communication. It is alsothe only practical choice at this time fordesignation as the official first languageof international radiotelephony commu-n i c a t i o n s .

Although Annex 10 to the ChicagoConvention recommends that air-gro u n dradiotelephony communications be con-ducted in the language normally used bythe station on the ground, it also re c o g-nizes that this is not always practical.Annex 10 elaborates with a re c o m m e n-

AERONAUTICAL COMMUNICAT I O N S

ICAO JOURNAL24

P rovisions for pro ficiency in common aviationlanguage to be stre n g t h e n e d

The potential consequences of an aviation mishap resulting from ambiguous communications or lack of language pro ficiency are serious enough that experts are reviewing ways to address the issue as a matter of priority.

EL I Z A B E T H MAT H E W S

EM B RY RI D D L E AE R O N A U T I C A L UN I V E R S I T Y

( UN I T E D STAT E S)

In the case of international aviation, the need to use a single, common language is universally acknowledged.

T

collision between KLM and Pan American747s at Tenerife with heavy loss of life, apilot’s choice of words (“we are now att a k e - o ff”) contributed to the uncert a i n t ys u rrounding the accident.

C e rt a i n l y, in the Tenerife accident in1977, as in all aviation accidents, a num-ber of factors and circumstances con-tributed to the error chain. When anAvianca airliner destined for New Yo r k ’ sJFK International Airpor t ran out offuel and descended into a suburb inJ a n u a ry 1990, clearly one of the con-tributing factors was the insuff i c i e n tquantity of fuel; another factor, however,seems to have been the breakdown ofe f fective communication between thec re w and ATC about the urgency of thelow-fuel situation. Following theAmerican Airlines accident near Cali,Colombia in 1995, the air traf fic con-t roller told investigators that he knewthe information given by the flight cre wwas inconsistent with the intent of theclearance he had issued. If the contro l l e rhad shared a common language with thepilot, he would have been able to seekclarification from the cre w. In fact, clari-fication and negotiation of meaning isone of the higher level language skillsmost important for clear communication.

E x p e rts predict that a further re d u c t i o nin the airline accident rate is dependent, in

l a rge measure, on adopting improved pro-c e d u res that take account of human fac-tors. In this context, the convening of thePRICE Study Group is considered timely.It provides an opportunity for an appro p r i-ate international and multilateral eff o rt top ropose a common language for inter-national operations, a development thatwould promote safety.

A l t e rnatives that circumvent the needto establish use of a common languagemay fail to enhance safety. At times,i n t e r p reters have been employed on theflight deck to facilitate communicationsbetween airc rew and ATC. Long flightssometimes make this option impractical,but more import a n t l y, interpreters addan additional layer between the two keyagents — controller and pilot — furt h e rcomplicating communication. In ro u t i n esituations, the use of an interpre t e rmight suffice. In unusual circ u m s t a n c e sor during an emerg e n c y, however, anyp ro c e d u re that slows down communica-tion becomes unacceptably cumbersomeand even dangero u s .

Some experts hope that data link sys-tems will mitigate the need for a com-mon language. While data link systemswill no doubt improve aviation commu-nications on some levels, possiblyi m p roving efficiency and safety, it is notat all clear that such systems will obviate

concept re p resented by its symbols (i.e. the words); it also means knowingpossible connotations to words andunderstanding their surrounding socialc o n t e x t .

Language is a highly complex and stilllittle understood interplay between theminds of the speaker and listener. It is ap rocess in constant flux. Languages con-vey infinite combinations of words andphrases because human thought ande x p ression is infinite and unpre d i c t a b l e .It is often highly ambiguous and depend-ent upon context, culture and share di n f o rmation among speakers. Art i f i c i a llanguage development groups admit that natural language, while being thesimplest form of communication forhumans, is the hardest for a computer to master. This is indicative of thee x t remely complex nature of the com-munication systems most humans takee n t i rely for granted.

Understanding the very complex natureof language assists in understandingwhy little or no pro g ress has been madein the development of a more suitablef o rm of speech. There simply is no moresuitable form of speech than natural l a n-guages for human communication. None-t h e l e s s, the need to achieve impro v e dradiotelephony communication ande n h a n c e d aviation safety by establishinga common radiotelephony language isv e ry clear. Current practice, with Eng-lish not always being used for a i r -g round communications and withoutuniversally applied standards for Eng-lish language pro f i c i e n c y, is pro v i n gi n c reasingly inadequate as the volume ofi n t e rnational air traffic rises. Indeed, itis possible to cite numerous incidentsattributable at least in part to inadequateEnglish language pro f i c i e n c y.

The importance of good communica-tion can be expressed in two ways. Poorcommunication, or lack of a mutual pro-ficiency in a shared common language,can be a causal factor in an accident.Equally important, good communicationcan play a role in preventing a safetyb reakdown which has a non-languagerelated cause. In the seconds before the

AERONAUTICAL COMMUNICAT I O N S

25NUMBER 3, 2001

Experts predict that a further reduction in the airline accident rate largely dependson adopting procedures that take account of human factors.

need to continue their work to impro v ep ro c e d u res and phraseologies, identify-ing and possibly changing standard i z e dphraseologies which may lend them-selves to ambiguity.

The field of aviation communicationsis ripe for further serious inquiry tobuild upon the useful work alre a d yaccomplished by some linguists andhuman factors specialists, and the avia-tion community might well considerfunding the re s e a rch of linguistic expert s .

The burden for improved communica-tion falls as much on native speakers asit does on second language users. Wi t hthe establishment of English as the lan-guage for international aviation com-m unications comes a re q u i rement tore i n f o rce strict adherence to standardphraseology on the part of pro f i c i e n tspeakers, and to apply effective radio-telephony techniques (e.g. desirableenunciation and rate of speech). There ismuch anecdotal evidence of the diff i c u l-ties caused by the use of non-standardp h r a s e o l o g y, particularly for users ofEnglish as a second language. Againstthe background of a linguistic educationcampaign within the aviation c o m m u n i-t y, the need for closer conf o rmity tos t a n d a rd phraseology and for gre a t e rc a re in communication on the par t ofnative and non-native speakers alikebecomes readily appare n t .

The implementation of an ICAO stan-d a rd for English language pro f i c i e n c yhighlights a number of needs within theaviation community. The first is to estab-

lish the re q u i rement for p ro f i-ciency in ever y-day English.While ATC communication is, atleast superf i c i a l l y, distinct fro mv e rnacular speech, the need foran understanding of commonEnglish can arise quickly in non-routine or emergency situations.Such circumstances may re q u i rethat a controller or pilot re a c hbeyond the scope of standard-ized phraseologies. In addition,a pilot or controller not infre-quently encounters the need to clarify communications, to

e x p l o re intent or to negotiate for mean-ing. All such linguistic demands might lie beyond the abilities of an individualwhose language proficiency is limited to the specific realm of standard i z e dp h r a s e o l o g i e s .

The second overarching considerationis the amount of instruction that pro-duces the level of proficiency re q u i re dfor safe operations. There is, alas, no sil-ver bullet, no magic pill for languagel e a rning. While re s e a rch does not seemto bear out the conventional wisdom thatc h i l d ren learn more readily than adults,it is undeniable that acquisition of stro n glanguage skills among adult learn e r stakes a considerable investment of timeand concentrated ef f o rt. An adult begin-ner might re q u i re a year of intensivetraining to attain the appropriate level ofp ro f i c i e n c y. Experience shows that 200hours of intensive language training isre q u i red to demonstrate marked impro v e-m e n t in language pro f i c i e n c y.

In order to facilitate compliance withan English language proficiency stan-d a rd, States will need access to a univer-sal rating scale of language pro f i c i e n c y.The PRICE Study Group is surv e y i n gthe existing rating scales — and therea re many — to determine their appro p r i-ateness to aviation. There is also the

the re q u i rement for good oral commu-nication skills. There will continue to bea need for oral communication in non-routine or emergency situations and asa backup for system failure. Secondly,c u rrent data link technology makes useof English. Pilots and controllers mustbe able to read the language, for transla-tion technology remains unproven giventhe rigorous demand for re l i a b i l i t y.

Attempts to create and pro m u l g a t ea rtificial languages — Esperanto, forinstance — have had little impact.

The case for English as the languageof international civil aviation is highlypragmatic. Because language is soclosely tied to our sense of national andcultural identity, people are naturally sen-sitive to issues of language use and policy.Although language policies are nevercompletely neutral, it is equally true thata language in itself is neither good norbad. In the case of international aviation,the need for a single, common languageis universally acknowledged.

The choice of English for intern a t i o n a laviation communications is more a toolfor enhancing safety than anything else,and the re q u i rement to use a commonlanguage is simply one more safety tool.

Establishment of a single commonlanguage for universal use in ATC com-munications will not eliminate all com-munication problems, however. English,after all, has long been available “onrequest” in international aviation, yetp roblems exist with standards of Englishp ro f i c i e n c y. Communication misunder-standings occur even between nativespeakers because any language givesrise to aviation’s greatest communicativechallenge: ambiguity.

Many incidents resulting from theambiguous use of ATC phraseology havebeen documented. Establishing a singlecommon language for inter n a t i o n a lradiotelephony communications will cer-tainly not eliminate the potential for thisp roblem, but it will in time significantlyi m p rove communication pro c e d u re soverall. Meanwhile, aviation specialists— perhaps increasingly seeking inputf rom the linguistic community — will

AERONAUTICAL COMMUNICAT I O N S

ICAO JOURNAL26

Elizabeth Mathews is Director of academic and avia-tion English language programmes at Embry RiddleAeronautical University, Daytona Beach, Florida,United States. Currently on a leave of absence fromEmbry Riddle, she is working as an aviation Englishc o n s u l t a n t .

continued on page 41

While ATC communication is distinct from vern a c u-lar speech, the need for a wider understanding ofEnglish can arise quickly in a non-routine situationwhich demands use of nonstandard phraseology.

Full Pro fic i e n c y

Advanced Pro fic i e n c y

Moderate Pro fic i e n c y

Limited Pro fic i e n c y

A b n o rm a lS i t u a t i o n

user in distress. The vast area covered bysatellites and the rapidity of satellitetracking have transformed SAR serv i c e sall over the globe. Since the SAR system’sb re a k t h rough into the space age, bothe m e rgency transmitters and theC O S PA S - S A R S AT satellite system havebeen dramatically impro v e d .

In the first working application of spacetechnology for SAR, several satellitesw e re put in low-altitude earth, near polar,orbits (LEO). Their purpose was to re c e i v etransmissions from emergency beaconsand to relay these to a network of dedi-cated ground stations. This system is nowenhanced by a constellation of geosta-t i o n a ry (GEO) satellites which can re-ceive signals from 406 megahertz (MHz)beacons and are capable of pro v i d i n galmost immediate distress alerts for the406 MHz beacons in their field of view.While the geostationary satellites do notp rovide coverage of the poles (their foot-print extends only from 75 degrees nort hto 75 degrees south), global coveragecontinues to be provided by the 406 MHzsystem utilizing the LEO satellites. ADoppler location pro-cessing system p ro v i d e san ac cur acy r a n g i n gf rom 12 to 20 k i l om e t re sfor 121.5 MHz b e a c o n sand three to five kilo-m e t res for 406 MHzb e a c o n s .

The SAR system basedon geostationary satel-lites provides detectiono n l y, but new generation406 MHz beacons mayp rovide a location whenthe transmitting beacon

is encoded with position data, either byway of a built-in satellite navigation re c e i v-er or by external navigation data input.To g e t h e r, the two satellite systems pro v i d ea comprehensive, complementary arr a n g e-ment for SAR: extensive coverage on 121.5MHz, and more accurate global cover-age on 406 MHz, with virtually instanta-neous coverage for 406 MHz beaconswhen transmitting between the 75-degre ep a r a l l e l s .

As the overall COSPA S - S A R S AT sys-tem has come to offer increased eff i c i e n-cies, the elements of older technology arebeing left behind. Consequently, the 121.5 MHz beacons, despite being avail-able at very low cost, have come to bec o n s i d e red a poor investment. They arethe source of a very large number of falsea l e r ts; in fact, over 98 per cent of all 121.5 MHz aler ts prove to be false.F u rt h e rm o re, these beacons have noautomatic identification facility and theirengineering specifications cannot be eas-ily improved. With recent amendments to annexes to the Chicago Convention,ICAO re q u i res carriage of emerg e n c y

HE essence of successful searc hand rescue (SAR) lies in the time-liness of the alert, location and

rescue eff o rt, and satellite technology pro-vides the most ef fective tool yet in locat-ing a crash site. However, while suchtechnological innovations are having apositive impact on SAR effectiveness, theyalso redefine the scope for human erro r.

Satellite detection has vastly impro v e dthe usability of emergency beaconswhich, until the COSPA S - S A R S AT* s y s-tem was commissioned in 1984, relied ono v e rflying aircraft for crash detection.

The cooperative initiative driving theC O S PA S - S A R S AT system is altogether inkeeping with SAR philosophy. Four Statep a r ties are funding the SAR space seg-ment packages: Canada, France, theRussian Federation and the United States.In all, 32 countries and organizations aref o rmally associated with the pro g r a m m e ,and 20 par ticipants provide and operateg round stations.

The COSPA S - S A R S AT ground stationscomprise local user terminals (LUTs) andmission control centres (MCCs). Thelocal user terminals resolve the signalsreceived from emergency beacons via thesatellites into distress positions, while themission control centres coordinate anddistribute alert and location data.

The COSPA S - S A R S AT system is avail-able to all States on a non-discriminatorybasis and is free of charge for the end-

SEARCH AND RESCUE

Satellite technology has transformed searc hand rescue services all over the globe

Advances in technology have greatly improved the effectiveness of search and rescue eff o rts. Toobtain the full benefit of this technology, however, the functioning of the human elements in the system needs to be carefully assessed.

BR I A N DAY

ICAO SE C R E TA R I AT

27NUMBER 3, 2001

Satellite detection has vastly improved the usability ofemergency beacons. The 121.5 MHz beacons, however, arethe source of a very large number of false alerts, and systemp rocessing of these ELTs may be discontinued after 2008.

* C O S PAS: space system for search of vessels in dis-t ress; SARSAT: search and rescue satellite-aidedt r a c k i n g .

T

SEAR CH AND R ESCUE

ICAO JOURNAL28

simultaneous access to position dataderived from both radar and ADS. Whenan alerting signal is received, for exam-ple, the two presentations of aircraft posi-tion and track appear very close together.The normal ADS signal re p o rting rate isonce every 45 seconds, although the con-t roller can increase the rate to once every15 seconds during an emerg e n c y.

While Norway has been able to intro-duce these arrangements because of thelocation of a suitable satellite, it is notlikely that many similar systems will beestablished specifically for SAR purposes.An ADS facility cannot be considered as asubstitute for the carriage of an ELT. Inthe event of a crash, ADS-derived signalswould stop transmitting, while the ELTcontinues to transmit a position afterimpact and, at sea, identifies the actualposition of survivors re g a rdless of thee ffect of drift.

Digital elevation mappingAnother application of satellite tech-

nology likely to have increasing applica-tion to all kinds of tactical operations,including SAR, is satellite-derived digitalelevation mapping. A digital elevationmodel (DEM) is an ord e red array of pointm e a s u rements of elevation above a p a r ticular re f e rence. This grid may alsobe re f e renced to some geographic c o o r-

dinate system that d e f i n e sthe horizontal position ofthe points, thus pro v i d i n ga three-dimensional dis-p l a y. Digital elevation mod-elling now available ishighly precise and incre a s-ingly af f o rdable, beingavailable “off the shelf.”

DEM technology israpidly changing the meth-ods by which tactical opera-

tions are planned, trained for, andultimately exercised. They provide rapidacquisition, dissemination and analysis ofdata. These are important factors in pro-viding tactical teams with up-to-date intel-ligence, and are a decided operationaladvantage. Their application to aero n a u t i-cal SAR is easy to envisage, part i c u l a r l y

during the rescue and re c o v e ry phase, andone of the applications currently beingevaluated in Europe is in alpine re s c u e .

DEM technology, in other words, couldallow searches with more precision andc e rt a i n t y. Variables such as sweep width,track spacing and search altitude may bed e t e rmined with greater exactness. Inestablishing forw a rd field bases, line-of-sight communications facilities may besited more accurately and rapidly, thussimplifying radio frequency pro p a g a t i o nanalysis and reducing clutter. Routing ofg round parties can be optimally deter-mined before personnel enter the field.

System stabilityWith implementation of advanced tech-

nologies, the task of finding a crash site isnot only simpler and quicker, but per-formed with fewer resources than in thepast, thus reducing the cost. More impor-tant still, the essential goal of SAR — savinglives — is more likely to be successfullymet. This does not mean, however, thatSAR planners can now rest on the benefit sof technology and let the system benignlyevolve to greater effic i e n c i e s .

While recent technological innovationsa re increasing SAR effectiveness, thepotential remains for human error toc o m p romise system re l i a b i l i t y. Av i a t i o n ,and SAR in part i c u l a r, is a domain inwhich failures are hard to predict and dif-ficult to prevent. The civil aviation indus-t ry is extraordinarily safe, but theconsequences of errors and violationsmay be extreme. For this reason, highreliability is very important in all aspectsof aviation. To achieve re l i a b i l i t y, a systemmust also have stability — that is, the sys-tem’s pro c e d u res, functions and re s p o n-sibilities need to be clearly established,fully understood, expertly perf o rmed andsmoothly coord i n a t e d .

The effectiveness of communication isa vital aspect of team coordination and is,p e rhaps, the most vital activity in the re s-cue coordination centre. Managers musttake responsibility for developing stro n gteam communication skills. The key ele-ment in effective team coordination isverbal communication.

locator transmitters (ELTs) operating on406 MHz by all new aircraft from 2002,and all aircraft beginning in 2005. Thesebeacons are also re q u i red to be fittedwith a low power transmitter operating on121.5 MHz to allow final homing bys e a rch aircraft once they reach the vicinityof the crash site. System processing of121.5 MHz ELTs may be discontinuedf rom 2008.

The capacity of 406 MHz ELTs totransmit their identification is, in itself, amajor advance. Once the rescue coord i-nation centre (RCC) has the encodedi n f o rmation on hand, it usually takes onlya short time to establish contact with thea i rcraft owner or operator, verify the alertand initiate SAR action. This process, sim-ple and direct though it is, re q u i res thatall ELTs be properly coded and re g i s-t e red by users in formal databases, asre q u i red by ICAO pro v i s i o n s .

N o rwegian innovationThe Norwegian Civil Aviation Adminis-

tration has made an innovative applicationof automatic dependent sur v e i l l a n c e(ADS) that greatly facilitates any searc hfor helicopters shuttling to oil rigs in theN o rth Sea. (ADS is a surveillance applica-tion in which position information from ana i rcraft’s flight management system istransmitted via data link to the ground sys-tem and presented to airt r a ffic controllers as airc r a f tsymbols on a traffic situa-tion display. )

The weather conditionsover the cold North Seaa re frequently extre m e ,and survival time in theevent of an aircraft ditch-ing is limited. The purposeof Norway’s ADS-basedsystem is to provide a re a l -time flight information and SAR alert i n gs e rvice for helicopter operations in thisinhospitable area. The typical timere q u i red for satellite processing of ADSre p o rts is four seconds, providing a veryaccurate, virtually continuous update ofthe aircraft’s position. This accuracy isevident when the air traffic controller has

hile recent

t e c h n o l o gical

innovations are

increasing SAR

effectiveness, the

potential for error

r e m a i n s

W

fic controllers and SAR mission coord i n a-tors alike. This ability, however, is sus-ceptible to disturbance by other visuali n f o rm a t i o n .

In the automated environment, SARc o o rdinators are subject to an incre a s i n gnumber of displays of information. Butt h e re is a point beyond which the displayof data becomes more of a burden thanbenefit, and RCC perf o rmance will deteri-

orate after that point is reached. RCCplanners need to bear this in mind.

Workload and perf o rm a n c eThe problem with workload for the

f ront-line operator is one of matching sup-ply (cognitive re s o u rces) with demand(the tasks of understanding, re m e m b e r-ing, decision making and taking action).With the introduction of new technology,some senses are stimulated more thanb e f o re and the distribution of workloadon the senses changes, with the pro s p e c tof one or more senses becoming over-loaded. An easy coping strategy has beento give complicated functions to the“machine” and force menial functionsonto the operator. Among these menialfunctions is the monitoring role. There isan irony in this, for while there are manyactivities in which human perf o rmance isinnately superior to that of a machine,

monitoring is not one of them.One concern with human perf o rm a n c e

is that short - t e rm memory may not beadequate. A person’s working memory iseasily compromised by the constant dis-traction of repetitive information fro me x t e rnal sources. Operations personnelwho are bombarded with graphic infor-mation are susceptible to mental over-load, diminishing their ability to fill a

monitoring role. On the other hand, theirs e n s o ry domain may remain highlyreceptive to speech and audio alarm ,meaning that a capacity to communicatet h rough phone lines or via radio may wellbe under-utilized. The work place, then,should be re a rranged to take account ofthese human limitations and capabilitiesand ensure that human re s o u rces aredeployed eff e c t i v e l y.

In summary, the introduction of moreautomated systems — whether satellite-or information-based — will have aninevitable impact on the job functions per-f o rmed in the rescue coordinating centreand on the skills re q u i red of operational

One newly introduced communicationsinnovation is the practice of “silent” hand-overs, a relay of information by meansother than the human voice. One of theoutcomes of silent hand-overs is thatsome parties previously involved in thep rocess can now be excluded. This canbe both beneficial and problematic. Onthe positive side, it may obviate one linkin a communication chain and remove as o u rce of e rro r. On the otherhand, i t downgrades whatmight be called aggregate sit-u a t i o n a l a w a re n e s s .

The matter of situationala w a reness is of critical impor-tance to RCC operations in twosignificant ways. The SAR mis-sion coordinator’s decision-making ability is dependent onit, and the RCC staff as a wholecan only properly integratetheir activities if they are accu-rately aware of the facts of thee m e rgency and how the situa-tion is evolving.

Situational awareness is ap re requisite for the safe opera-tion of any complex dynamicsystem. The safe separation ofs e a rch aircraft, a critical aspectof SAR mission coordination, re q u i re sclose concentration and highly developedmental skills. Teamwork in a re s c u ec o o rdination centre promotes situationala w a reness, which is essential to eff e c t i v ei n f o rmation processing and decisionmaking. Communication, as the connec-tor between every link in the pro c e s s ,may be the most vital RCC functionrequiring reassessment in an automatede n v i ro n m e n t .

T h e re are other, similarly critical con-nections. As much as anything, situationala w a reness depends on the capacity ofs h o rt - t e rm memory. Researchers tell usthat the part of memory concerned withmaintaining pictorial or image re p re s e n-tations (“getting the picture”) can onlyretain information in this form for shortperiods without active rehearsal. Thecompilation and retention of a mental pic-t u re is fundamental to the work of air traf-

SEARCH AND RESC UE

29NUMBER 3, 2001

Brian Day is a Technical Officer in the Air Tr a ff i cManagement (ATM) Section of the Air NavigationBureau at ICAO headquarters, Montreal. Mr. Day isresponsible for search and rescue matters, and is alsothe Secretary of the ICAO Proficiency Requirements inCommon English (PRICE) Study Group.

continued on page 41

Using advanced technologies, the task of finding a crash site is not only simpler and quicker,but performed with fewer resources than in the past.

800 was to be the first leg of a scheduledthree-day trip sequence for the four flightcrew members. A captain occupied theleft front seat, a captain/check airmanoccupied the right front seat, a flightengineer occupied the right aft seat(flight engineer position), and a flightengineer/check airman occupied the leftaft seat (cockpit jump seat). TWA Flight800 was scheduled to depart JFK forCDG about 1900; however, the flight wasdelayed because of a disabled piece ofground equipment and concerns about asuspected passenger/baggage mis-match. According to the cockpit voicerecorder (CVR), at 1959:44, gate agentpersonnel advised the flight crew that,although a passenger’s bag had beenpulled because they suspected that it wasunattended, they subsequently con-firmed that “the passenger was on boardthe whole time.” The CVR recorded thesound of the cockpit door closing at1959:59, and the flight crew continued toprepare for departure.

T WA Flight 800 was pushed back fro mthe gate about 2002. According to the

CVR, between 2005 and 2007:46, the fli g h tc rew started the Nos. 1, 2, and 4 enginesand completed the after-start checklist. At2007:52, the captain/check airm a nadvised the JFK gate hold controller thatT WA Flight 800 was “ready to taxi.” About2008, the flight crew received taxi instru c-tions from air traffic control (ATC) andbegan to taxi to Runway 22R, the depar-t u re ru n w a y. While the aircraft was taxi-ing (about 2014), the CVR re c o rded theflight crew starting the No. 3 engine andconducting the delayed engine-start andtaxi checklists.

At 2017:18, the CVR recorded ATCstating, “TWA 800 heavy caution waketurbulence from a 757, Runway 22R, taxiinto position and hold.” The CVR tran-script indicated that the captain/checkairman acknowledged the ATC clearanceand that the aircraft was taxied into posi-tion on the departure runway. At 2018:21,ATC advised the pilots of TWA Flight 800that the wind was out of 240 degrees ateight knots and cleared Flight 800 fortakeoff on Runway 22R. The CVR record-ed the flight crew conducting the beforet a k e - o f f checklist and the sound ofi n c reasing engine noise; flight datarecorder (FDR) and CVR informationindicated that the aircraft became air-borne about 2019.

During the aircraft’s departure fromJFK, the pilots of TWA Flight 800received a series of (generally increas-ing) altitude assignments and headingchanges from New York Terminal RadarApproach Control and Boston air routet r a ffic control centre (ARTCC) con-t rollers. At 2025:41, Boston ART C Cadvised the pilots to “climb and maintain[19,000] feet and expedite thro u g h

ON 17 July 1996, about 2031 east-e rn daylight time, Trans Wo r l dAirlines, Inc. (TWA) Flight 800,

a Boeing 747-131 crashed in the AtlanticOcean near East Moriches, New Yo r k .T WA Flight 800 was operating as ascheduled international passenger flightf rom John F. Kennedy International Air-p o rt (JFK), New York, New York, toCharles de Gaulle International Airport(CDG), Paris, France. The flight depart-ed JFK about 2019, with two pilots, twoflight engineers, 14 flight attendants and212 passengers on board. All 230 peopleon board were killed, and the airc r a f twas destroyed. Visual meteoro l o g i c a lconditions prevailed for the flight, whichoperated on an instrument flight ru l e s(IFR) flight plan.

On the day of the accident, the airc r a f td e p a rted from Athens, Greece, as TWAFlight 881 about 0537, landed at JFKabout 1631, and arrived at Te rminal 5,Gate 27 about 1638. The flight crew thathad flown the aircraft from Athens,G reece, to JFK told National Tr a n s-p o r tation Safety Board (NTSB) investi-gators that they had not observed anyoperational abnormalities during thatflight. A scheduled flight crew changeo c c u rred at JFK. The accident airc r a f twas refuelled at JFK and remained atGate 27 with the auxiliary power unit(APU) and two of its three air condition-ing packs operating (for about 2.5 hours)until it departed as TWA Flight 800.

According to company records, Flight

ACCIDENT R EPORT

ICAO JOURNAL30

NTSB issues report on TWA Flight 800i n flight breakup over Atlantic Ocean

The probable cause of the inflight breakup of the Boeing 747-100 was an explosion of the centre wingfuel tank resulting from ignition of the flammable fuel/air mixture in the tank, although the sourc eof the ignition energy could not be determined with cert a i n t y.

NAT I O N A L TR A N S P O RTAT I O N

SA F E T Y BO A R D

( UN I T E D STAT E S)

T WA FLIGHT 800 REPORTThis article comprises extracts from the U.S.NTSB re p o rt on the accident involving TWAFlight 800, which experienced an inflightb reakup and then crashed into the Atlantic Oceannear East Moriches, New York on 17 July 1996( A i rcraft Accident Report NTSB/AAR-00/03). The re p o rt was adopted by the NTSB on 23 August 2000.

The full accident report can be viewed at theNTSB website (http://www.ntsb.gov) and may bepurchased in paper form from the NationalTechnical Information Service (Report No. PB2000-910403); tel. (800) 553-6847 or (703) 605-6000.

loud sound” for a fraction of a second(0.117 second) on all channels immedi-ately before the recording ended. Theaccident aircraft’s last re c o rded radartransponder return occurred at 2031:12,and a review of the FDR data indicatedthat the FDR lost power at 2031:12.

A c c o rding to the Boston ARTCC tran-script, at 2031:50, the captain of anEastwind Airlines Boeing 737 (StingerBee Flight 507) re p o rted that he “just sawan explosion out here.” About 10 secondsl a t e r, the captain of Stinger Bee Flight 507f u rther advised “we justsaw an explosion up aheadof us here ... about 16,000feet or something like that,it just went down into the water. ”2 S u b s e q u e n t l y,many ATC facilities in theNew York/Long Islanda rea received re p o rts of anexplosion from other pilotsoperating in the are a .

Many witnesses in thevicinity of the accidentstated that they sawand/or heard explosions,accompanied by a larg ef i reball over the ocean, and observ e ddebris, some of which was burn i n g ,falling to the water. According to witnessdocuments, about one-third of these wit-nesses reported that they observed astreak of light, resembling a flare, mov-ing upward in the sky to the point wherea large fireball appeared. Several wit-nesses reported seeing this fireball splitinto two fireballs as it descended towardthe water.

Pieces of the aircraft wreckage wered i s c o v e red floating on and beneath thes u rface of the Atlantic Ocean about eightmiles south of East Moriches, New Yo r k .The main wreckage was found on theocean floor, between 40°37’42” and40°40’12” north latitude and 72°40’48”and 72°35’38” west longitude. The acci-dent occurred in dusk lighting conditions.

Investigation findings1. The flight crew was properly certifica-ted and qualified and had received the

training and off-duty time prescribed byfederal regulations. No evidence indicatedany pre-existing medical or behaviouralconditions that might have adverselyaffected the flight crew’s performance.2. The aircraft was certificated, equippedand dispatched in accordance with federal regulations and approved TWAprocedures.3. At the time of the accident, there werelight winds and scattered clouds in thearea, but there were no significant mete-o rological conditions that might have

disrupted the flight.4. The infli g h tb reakup of TWA Flight 800was not initiated by a pre-existing condi-tion resulting in a structural failure anddecompression.5 . The inflight breakup of TWA Flight 800was not initiated by a bomb or a missile strike.6. The fuel/air vapour in the ullage ofTWA Flight 800’s centre wing fuel tank(CWT) was flammable at the time of theaccident.7. A fuel/air explosion in the centre wingfuel tank of TWA Flight 800 would havebeen capable of generating suf f i c i e n tinternal pressure to break apart the tank.8 . The witness observations of a stre a kof light were not related to a missile, andthe streak of light re p o rted by most ofthese witnesses was burning fuel fro mthe accident aircraft in crippled flightduring some portion of the post-explo-sion pre-impact breakup sequence. Thewitnesses’ observations of one or moref i reballs were of the aircraft’s burn i n g

[15,000 feet]”; the pilots acknowledgedthe instructions at 2025:47. According tothe CVR, at 2026:24, Boston ART C Camended TWA Flight 800’s altitude clear-ance, advising the pilots to maintain13,000 feet mean sea level (msl). At2027:47, the CVR recorded the sound ofthe altitude alert tone, and the FDR dataindicated that the aircraft reached itsassigned altitude.

At 2029:15, the CVR recorded the cap-tain stating, “Look at that crazy fuel flowindicator there on number four ... seethat?” At 2030:15, Boston ART C Cadvised, “TWA 800 climb and maintain[15,000 feet msl].” The CVR recorded thecaptain stating “climb thrust” and thecaptain/check airman acknowledgingthe ATC clearance at 2030:18. At 2030:25,the captain repeated “climb thrust” andat 2030:35, the flight engineer responded“power’s set.” The CVR recording of thenext 30 seconds from the cockpit areamicrophone (CAM) includes the follow-ing sounds:•a sound similar to a mechanical move-ment in the cockpit (at 2030:42),•an unintelligible word (at 2031:03), and•sounds similar to recording tape dam-age noise (at 2031:05).1

At 2031:12, the CVR recording ended.A sound spectrum study of the informa-tion recorded by the CVR revealed thattwice within the last second of the CVRrecording (about 0.73 and 0.68 secondsbefore the recording stopped), the cap-tain’s channel recorded harmonic tonesat the 400 Hertz (Hz) frequency, but itdid not record other electrical systembackground noise that it had recordedp reviously throughout the re c o rd i n g .These other electrical system back-g round noises were re c o rded on theother CVR channels without interrup-tion. The CVR then recorded a “very

ACCIDENT REPORT

31NUMBER 3, 2001

T WA Flight 800 wreckage location relative to the airc r a f t ’sflight path, JFK International Airport, and Long Island.

1. Subsequent examination of the CVR tape indicat-ed that these sounds were likely the result of waterdamage to the tape head. Because of the position ofthe tape on the reels, the portion of the tape that con-tained sounds from the last seconds before the CVRstopped re c o rding was exposed to water after thea c c i d e n t .2. Radar data and ATC re c o rds indicated that StingerBee Flight 507 was about 20 to 25 miles northeast ofT WA Flight 800, on a southwesterly heading.

13. Electromagnetic interference frompersonal electronic devices played norole in igniting the fuel/air vapour inTWA Flight 800’s centre wing fuel tank.14. It is unlikely that electromagneticinterference from aircraft system wiringplayed a role in igniting the fuel/airvapour in TWA Flight 800’s centre wingfuel tank.15. Existing standards for wire separa-tion may not provide adequate protectionagainst damage from short circuits.16. A short circuit producing excess

voltage that was transferred to the centrewing tank fuel quantity indication systemwiring is the most likely source of igni-tion energy for the TWA Flight 800 cen-tre wing tank explosion.17. Silver-sulfide deposits on fuel quanti-ty indication system components insidefuel tanks pose a risk for ignition of flam-mable fuel/air vapour.18. The ignition energy for the centrewing fuel tank explosion most likelyentered the centre wing tank through thefuel quantity indication system (FQIS)wiring, and, although it is possible thatthe release of ignition energy inside theCWT was facilitated by the existence ofsilver-sulfide deposits on an FQIS com-ponent, neither the energy release mech-anism nor the location of the ignition

inside the CWT could be determinedfrom the available evidence.19. Failure modes and effects analysesand fault tree analyses should not berelied upon as the sole means of demon-strating that an aircraft’s fuel tank systemis not likely to experience a catastrophicfailure.2 0 . A fuel tank design and cert i f i c a t i o nphilosophy that relies solely on the elimina-t i o n of all ignition sources, while acceptingthe existence of fuel tank fla m m a b i l i t y, isfundamentally flawed because experi-ence has demonstrated that all possibleignition sources cannot be predicted andreliably eliminated.2 1 . Operating transport - c a t e g o r y air-craft with flammable fuel/air mixtures infuel tanks presents an avoidable risk ofan explosion.2 2 . The placement of heat-generatingequipment under a fuel tank containingJet A fuel can unnecessarily increase theamount of time that the aircraft is operat-ing with a flammable fuel/air mixtureunless measures are in place to either (1)p revent the heat from entering the centrewing fuel tank or (2) eliminate the fla m-mable vapour inside the centre wing tank.23. The condition of the wiring systemin the aircraft was not atypical for an air-craft of its age, and the aircraft was main-tained in accordance with pre v a i l i n gaccepted industry practices.24. Until recently, insufficient attentionhas been paid to the condition of aircraftelectrical wiring, resulting in potentialsafety hazards.2 5 . The issues defined in the FederalAviation Administration’s Aging Tr a n s-p o r t Non-Structural Systems Plan arei m p o rtant safety issues that must befully addressed through appro p r i a t echanges, including ru l e m a k i n g .

P robable causeThe NTSB determines that the pro b a-

ble cause of the TWA Flight 800 acci-dent was an explosion of the centrewing fuel tank, resulting from ignition ofthe flammable fuel/air mixture in thetank. The source of ignition energy forthe explosion could not be determ i n e d

w reckage falling toward the ocean.9. The TWA Flight 800 inflight breakupwas initiated by a fuel/air explosion inthe centre wing fuel tank.10. Boeing’s design practice that per-mits parts less than three inches long inany direction to be electrically unbondedmay not provide adequate pro t e c t i o nagainst potential ignition hazards createdby static electricity generated by light-ning or other high-energy discharges.11. It is very unlikely that the flammablefuel/air vapour in the centre wing fuel

tank on TWA Flight 800 was ignited by alightning or meteor strike; a missile frag-ment; a small explosive charge placed onthe CWT; auto ignition or hot surfaceignition, resulting from elevated temper-atures produced by sources external tothe CWT; a fire migrating to the CWTf rom another fuel tank via the vent(stringer) system; an uncontained en-gine failure or a turbine burst in the airconditioning packs beneath the CWT; amalfunctioning CWT jettison/overr i d epump; a malfunctioning CWT scavengepump; or static electricity.12. Electromagnetic interference fromradio frequency sources external to TWAFlight 800 did not produce enough ener-gy to ignite the fuel/air vapour in the cen-tre wing fuel tank.

ACCIDENT REPORT

ICAO JOURNAL32

A photograph of the right side of the large three-dimensional reconstruction, withthe support scaffolding visible.

a d d ress (through rulemaking or othermeans) all of the issues identified in theAging Tr a n s p o rt Non-Structural SystemsPlan, including: the need for impro v e dtraining of maintenance personnel toe n s u re adequate recognition and repair ofpotentially unsafe wiring conditions; theneed for improved documentation andre p o rting of potentially unsafe electricalwiring conditions; and the need to incor-porate the use o f newt e c h n o l o g y, such asa rc-fault c i rcuit bre a k-ers and automated wiretest e q u i p m e n t .

P reviously issued re c -o m m e n d a t i o n s. As aresult of the TWA Flight800 accident investiga-tion, the Safety Boardissued the following safe -ty recommendations to the FAA on 13December 1996:• R e q u i re the development and imple-mentation of design or operationalchanges that will preclude the operationof transport-category aircraft with explo-sive fuel/air mixtures in the fuel tanks:(a) Significant consideration should begiven to the development of airc r a f tdesign modifications, such as nitro g e n -i n e rting systems and the addition of insulation between heat-generatingequipment and fuel tanks. Appro p r i a t em o d i fications should apply to newly cer-t i ficated aircraft and, where feasible, toexisting airc r a f t .(b) Pending implementation of designm o d i fications, re q u i re modifications inoperational pro c e d u res to reduce thepotential for explosive fuel/air mixture sin the fuel tanks of transport - c a t e g o rya i rcraft. In the 747, consideration shouldbe given to refuelling the centre wingfuel tank before flight whenever possiblef rom cooler ground fuel tanks, pro p e rmonitoring and management of theCWT fuel temperature, and maintainingan appropriate minimum fuel quantity inthe CWT.•Require that the 747 Flight Handbooksof TWA and other operators of 747s andother aircraft in which fuel tank tempera-

t u re cannot be determined by flightcrews be immediately revised to reflectthe increases in centre wing fuel tankfuel temperatures found by flight tests,including operational pro c e d u res toreduce the potential for exceeding CWTtemperature limits.•Require modification of the centre wingfuel tank of 747 aircraft and the fuel tanksof other aircraft that are located near

heat sources to incorpo-rate temperature probesand cockpit fuel tank tem-perature displays to per-mit determination of fueltank temperatures.

As a result of this acci-dent investigation, theSafety Board also issuedthe following recommen-dation to the FAA on 18

February 1997:•Develop and implement pro c e d u re s ,including a checklist of safety-re l a t e ditems, for the handling and placement ofexplosive training aids by K-9 explosivesdetection teams to prevent contamina-tion of aircraft and airport facilities and toensure an effective K-9 explosives detec-tion programme.

As a result of this accident investiga-tion, the Safety Board also issued the fol-lowing recommendations to the FAA on7 April 1998:•Issue, as soon as possible, an airw o rt h i-ness directive to require a detailed ins-pection of fuel quantity indication systemwiring in Boeing 747-100, -200, and -300series aircraft fuel tanks for damage, andthe replacement or the repair of any wire sfound to be damaged. Wi res on HoneywellSeries 1-3 probes and compensatorsshould be removed for examination.•Issue an airw o rthiness directive torequire the earliest possible replacementof the Honeywell Corporation Series 1-3terminal blocks used on Boeing 747 fuelprobes with terminal blocks that do nothave knurled surfaces or sharp edgesthat may damage fuel quantity indicationsystem wiring.•Conduct a sur vey of fuel quant ity

with cert a i n t y, but, of the sources evalu-ated by the investigation, the most likelywas a short circuit outside of the centrewing fuel tank that allowed excessivevoltage to enter it through electricalwiring associated with the fuel quantityindication system.

Contributing factors to the accidentwere the design and certification conceptthat fuel tank explosions could be pre-vented solely by precluding all ignitionsources, and the design and certificationof the Boeing 747, with heat sourceslocated beneath the centre wing fuel tankwith no means to reduce the heat trans-ferred into the tank or to render the fuelvapour in the tank nonflammable.

The safety issues raised by the investi-gation include fuel tank flammability, fueltank ignition sources, design and certifi-cation standards, and the maintenanceand aging of aircraft systems. Safety rec-ommendations concerning these issuesare addressed to the Federal AviationAdministration.

NTSB re c o m m e n d a t i o n sNew recommendations issued to the

FAA. As a result of the investigation ofthe TWA Flight 800 accident, the NTSBmakes the following recommendationsto the Federal Aviation Administration(FAA):•Examine manufacturers’ design prac-tices with regard to bonding of compo-nents inside fuel tanks and re q u i rechanges in those practices, as necessary,to eliminate potential ignition hazards.•Review the design specifications for air-craft wiring systems of all U.S.-certifiedaircraft and (1) identify which systemsare critical to safety and (2) require revi-sions, as necessary, to ensure that ade-quate separation is provided for thewiring related to those critical systems.•Require the development and imple-mentation of corrective actions to elimi-nate the ignition risk posed by silver-sul-fide deposits on fuel quantity indicationsystem components inside fuel tanks.• R e g a rdless of the scope of the AgingTr a n s p o rt Systems Rulemaking AdvisoryCommittee’s eventual re c o m m e n d a t i o n s ,

ACCIDENT REPORT

33NUMBER 3, 2001

continued on page 39

he most likelysource of ignition

e n e r gy for the explosion was a shortcircuit outside of thecentre wing fuel tank

T

D i ff e rent policy options for pursuing ways to limit orreduce emissions of greenhouse gases are currently unders t u d y. One possibility under consideration is to expand ICAOAnnex 16 to specifically address emissions of global con-c e rn. Participants also were informed about the developmentof guidance material on the operational opportunities forreducing fuel consumption and emissions, and work ondeveloping a methodology for calculating the emissions ben-efits associated with the introduction of advanced CNS/AT Msystems. The substantial work that has been done on thepossible use of market-based measures — such as levies,emissions trading and voluntary measures — was alsore v i e w e d .

The various presentations that were made at the colloquium,as well as the summary presented by the ICAO CouncilP resident, can be viewed at ICAO’s website (www.icao.int) byfollowing the link to the meetings and conferences page. ■

Regional planning gro u pto meet in Cape Ve rd eThe next meeting of the Africa-Indian Ocean regional plan-ning and implementation group (APIRG/13) will take placef rom 25 to 29 June 2001 on Sal Island, Cape Ve rde. Theg roup, formed by ICAO in 1980 to ensure the continuous andc o h e rent development of the African regional plan, is meetingfor the 13t h time. Agenda items that will have a high priorityinclude a review of the Africa-Indian Ocean region air navi-gation plan and survey of each State’s shortcomings anddeficiencies in the area of air navigation services, the devel-opment of human factors strategies and the need for furtheri m p rovement in inter- regional coordination. ■

Over 200 participants from more than 50 States and some 20i n t e rnational organizations took part in an ICAO colloquiumon the environmental aspects of aviation which concluded on11 April. The event served to exchange views on enviro n-mental issues, and to familiarize States with the work of theICAO Committee on Aviation Environmental Pro t e c t i o n(CAEP), particularly the results of the Committee’s last meet-ing, in January 2001 (see “CAEP recommends further meas-u res for reducing aircraft noise, engine exhaust emissions,”Issue 1/2001, page 30).

The first two days of the three-day conference focused pri-marily on aircraft noise, with a general recognition of the needto address noise issues on a global basis, and widespre a dsupport for a balanced approach to noise management com-prised of four equally important elements: a reduction of air-craft noise at source; effective land-use planning and contro l ;wider use of noise abatement operating pro c e d u res; andoperating restrictions for the noisier aircraft types.

The colloquium re a ffirmed that ICAO, and particularlyC A E P, remains the most appropriate forum in which toa d d ress noise issues on an international basis.

In summarizing the views expressed at the closing of thecolloquium, ICAO Council President Dr. Assad Kotaite indi-cated that the balanced approach to the noise issue wouldlikely be re flected in a new resolution to be considered by the3 3rd ICAO Assembly this fall. In drafting a resolution on ICAOpolicies and practices for environmental protection, theCouncil, he stated, would bear in mind several principles thathad been enunciated at the colloquium, including the con-clusions that:•noise management should be considered only in the con-text of a balanced pro g r a m m e ;•the process for implementing the programme and balanc-ing its elements would be decided by States; and•the goal should be to achieve the maximum enviro n m e n t a lbenefit in the most cost effective manner.

The colloquium heard a wide range of views on the deli-cate question of possible operating restrictions on Chapter 3a i rcraft. While some States expressed the need to re s t r i c tcertain Chapter 3 aircraft at their airports, others re m a i n e ds t rongly opposed to any restrictions on aircraft that complywith the current Chapter 3 standards, which were adopted in1977. There is hope that a consensus on this complex issuewill be reached before the Assembly session in September.

N u m e rous factors would need to be considered by theCouncil in proposing any resolution that includes operatingrestrictions, Dr. Kotaite concluded, urging States to workwithin ICAO and on a bilateral and inter- regional basis in themonths ahead to find compromises that will enable the ICAOAssembly to resolve the pro b l e m .

The colloquium also devoted substantial time to theimpact of aircraft engine emissions on the environment, withfocus on global concern s .

ICAO JOURNAL34

ICAO U P D ATE E n v i ronmental colloquium facilitates exchange of views

I CAO Council President Dr. Assad Kotaite (centre) with ICAOS e c r e t a ry General R.C. Costa Pereira (right) and Jo n a t h a nA l e ck , Colloquium Moderator and Chairman of the A i rTransport Committee and Rep r e s e n t a t ive of Australia on theCouncil of ICAO . The colloquium of 9-11 April at ICAO head-q u a r t e rs in Montreal attracted over 200 participants from morethan 50 States and some 20 international orga n i z a t i o n s.

I FATCA has safety role to play,Council President tells gatheringAv i a t i o n ’s enviable safety re c o rd is the product of a deep-ro o t-ed commitment to optimum aviation safety on the part of oper-ators, manufacturers, regulators and service providers, ICAOCouncil President Dr. Assad Kotaite emphasized in his addre s sto the International Federation of Air Tr a ffic Contro l l e r s ’Associations (IFATCA) at a meeting in Geneva on 23 Marc h2001 that commemorated the federation’s 40t h a n n i v e r s a r y.

Among those active in aviation, “air traffic controllers carryout a particularly demanding task,” the Council Pre s i d e n tobserved. Although controllers may be supported by sophis-ticated systems and pro c e d u res, “they are ultimately alone inmaking critical control decisions. ... Without their dedicationand professionalism, civil aviation as we know it might note x i s t . ”

ICAO Council has recently granted IFATCA, the pro f e s s i o n-al organization that re p resents some 40,000 air traffic con-t rollers in more than 100 countries, status as an observer ata p p ropriate ICAO meetings. IFATCA plays a key role in pro-moting safety, the Council President stated, and its re g u l a rparticipation in ICAO regional and international meetings, pan-els and working groups will be a valuable contribution to theongoing effort to re fine and modernize the standards and re c-ommended practices contained in the technical annexes tothe Convention on International Civil Aviation (Chicago, 1944).

Given a forecast of 5 percent growth in passengers anda i rcraft movements per year over the next decade, the col-lective challenge of managing air traffic safely and eff i c i e n t l yin the years ahead will not be easy to address, Dr. Kotaiteacknowledged. “Bold, concerted and imaginative action” will

Name of panel changed toreflect new work pro g r a m m eThe Review of the General Concept of Separation Panel(RGCSP), which last met in Montreal in May 2000, has beengiven a new name that better reflects its activities. Nowknown as the Separation and Airspace Safety Panel (SASP),the ICAO Air Navigation Commission (ANC) agreed to thename change because the panel’s new work programme ismainly in the area of determining separation minima andexamining related airspace safety issues.

SASP is tentatively scheduled to hold its first meeting in late2003. The panel, whose members are nominated byContracting States, will advise the ANC on technically practicaland operationally feasible ICAO provisions that may be need-ed to meet the objectives specified in its work programme. ■

M o re safety oversight audit summaryreports disseminatedSeveral summary reports resulting from safety oversightaudits conducted by ICAO in the past year were disseminat-ed to the org a n i z a t i o n ’s Contracting States in recent months.The latest reports cover audits carried out for Chile, Côted ’ I v o i re, Kyrgyzstan, Senegal (a revised report) and Ta j i k i s t a n .Another 99 summary reports have been issued pre v i o u s l y.

Since ICAO audit activities commenced in March 1999, atotal of 161 States have been audited. As of 30 April 2001,131 correction action plans had been submitted by theStates audited. The goal of the ICAO universal safety over-sight audit programme is to complete audits of allContracting States by September 2001, when the 33rd I C A OAssembly will convene. ■

Council adopts amendments to annexes of the Chicago ConventionThe ICAO Council has adopted amendments to the standard sand recommended practices contained in several technicalannexes to the Convention on International Civil Aviation(Chicago, 1944). Most of the revisions, which were re c e n t l ydisseminated to States, will become applicable in November2001 with the exception of the amendment to Annex 8, whichdoes not become applicable until March 2004.

States that disapprove of any part of an amendment areexpected to register their disapproval with ICAO by 16 July2001. States are also expected to indicate by a certain datewhether any diff e rences exist between their national re g u l a-tions or practices and the amended annexes, as well as thedate by which they expect to achieve compliance with thep rovisions of the revised annexes.

The amendments adopted recently concern the followingannexes: Annex 1, Personnel Licensing; Annex 2, Rules ofthe Air; Annex 3, Meteorological Service for International AirN a v i g a t i o n; Annex 4, Aeronautical Charts; Annex 6, O p e r a t i o nof Aircraft; Annex 8, Airworthiness of Aircraft; Annex 10,Aeronautical Te l e c o m m u n i c a t i o n s; Annex 11, Air Tr a f f i cS e rv i c e s; Annex 12, Search and Rescue; Annex 13, A i r c r a f tAccident and Incident Investigation; Annex 14, A e r o d r o m e s( Volume 1, Aerodrome Design and Operations); Annex 15,Aeronautical Information Serv i c e s; and Annex 18, The SafeTransport of Dangerous Goods by Air. ■

35NUMBER 3, 2001

AIR LAW INSTRUMENTSThe Montreal Convention of 1999 was ratified byParaguay on 29 March 2001, bringing the number of rat-ifications to 11. Paraguay also ratified Article 83 b i s(Lease, charter or interchange) and Article 3 b i s ( N o n - u s eof weapons against aircraft), air law instruments whicha re already in force. The Montreal Convention was adopt-ed in May 1999 as the new regime to govern air carrierliability and will enter into force after it has received 30ratifications. To mark the occasion, Helena Felip Salazar,the Chargé d’Aff a i res of the Embassy of Paraguay inOttawa, is pictured with ICAO Acting Secretary GeneralVivek Pattanayak (centre) and Silvério Espínola of theICAO Legal Bure a u .

ICAO JOURNAL36

be re q u i red to deal effectively with the present and expect-ed airport and airspace congestion, he stated.

D r. Kotaite’s address focused on the key initiatives underway to promote safety and achieve a reduction in the num-ber and rate of aviation accidents worldwide. The global avi-ation safety plan that ICAO oversees is currently comprised oft h ree pillars: the universal safety oversight audit pro g r a m m e ,which consists of re g u l a r, mandatory, systematic and harmo-nized safety audits carried out by ICAO in all of itsContracting States; the flight safety and human factors pro-gramme, which seeks to further the understanding of the ro o tcauses of both human and organizational errors; and thec o n t rolled flight into terrain (CFIT) prevention pro g r a m m e ,which addresses systemic flaws and is directed at decisionmakers in the aviation system.

By assuming a global coordinating role, ICAO strives toh a rness the synergies of safety initiatives of groups ando rganizations worldwide that pursue similar objectives, Dr.Kotaite explained. In addition to coordinating the globale ffort, the global aviation safety plan determines priorities forI C A O ’s own safety-related activities, with emphasis on thoseactivities that offer the best safety dividends.■

Comments sought on proposed review of licensing and training standard sICAO Contracting States have been asked to comment by 20July 2001 on ICAO’s plan to review personnel licensing andtraining standards. If the response from States is positive,ICAO will proceed with establishment of a panel of expertsthat will review the flight crew training and licensing standard scontained in two of the annexes to the Chicago Convention— Annex 1, Personnel Licensing and Annex 6, Operation ofA i r c r a f t. Although the original review would be limited to fli g h tc rew licensing and training, it may be followed by similarreviews for other categories of aviation personnel.

ICAO perceives a need to review the standards becauseof the major developments in aircraft operations and trainingthat have taken place since the last revision to Annex 1 flightc rew specifications was initiated 20 years ago. Operators arenow using highly sophisticated aircraft operated by two cre w

members in an environment of increasing complexity. At thesame time, general aviation continues to use aircraft of atechnology that largely derives from the 1950s. Licensings t a n d a rds need to be able to cater for the widening spre a dbetween the diff e rent sectors of aircraft operation and the dif-f e rent aircraft and equipment being used.

In a number of States, ab initio training has taken on anew importance as the supply of pilots from general avia-tion and the military fails to keep up with demand. Thee m e rgence of training tools with the potential for better andfaster training calls for a careful re-examination of thelicensing credits based on these technologies. Finally, theneed for more effective training has compelled severalStates to develop competency training and licensingre q u i rements that incorporate more explicit criteria formeasuring competence.

While Annex 1 re q u i rements have stood the test of timesince the basic framework of the annex was first developed inthe 1940s, the absence of common criteria against which tom e a s u re the competence of flight crews has led to signific a n tvariations in the diff e rent performance standards which havebeen developed by States. In addition, an informal re v i e wcarried out by the ICAO Secretariat has revealed that the cur-rent standards have not been fully kept in line with the devel-opment of aviation both in terms of the content of trainingand in the use of modern training devices. ■

ICAO safety statistics for 2000The number of fatal aircraft accidents experienced in sched-uled air services worldwide last year declined slightly to 18,c o m p a red to 20 accidents in 1999, according to the latestICAO analysis of safety statistics. However, the pre l i m i n a r yf i g u res also show that the number of passenger fatalitiesi n c reased last year to 755 from 499 fatalities in 1999. Becauseof the higher number of fatalities in 2000, the passenger fatal-ity rate also rose, from approximately 0.020 fatalities per 100million passenger- k i l o m e t res in 1999 to 0.025 in 2000.

In non-scheduled services there were 22 fatal accidents in2000, unchanged from 1999. These accidents accounted for291 passenger deaths in 2000, compared to 129 fatalities in1999. (The figures cited here cover only those accidentswhich resulted in passenger fatalities and involved airc r a f thaving a maximum take-off mass of more than 2,250 kilo-g r a m s . )

T h e re were 27 acts of unlawful interference officially re p o r t-ed in 2000 in which 53 people were killed and 46 injured. Insome cases, the acts of unlawful interference resulted in air-craft accidents. ■

Boeing 747 did n o t crash in QatarAn article in ICAO Journ a l Issue 1/2001 (“New system allowsfor detection of unsafe aircraft loadings shortly before take-off , ”page 14), contained incorrect information about a Boeing 747accident that was reported to have occurred in Qatar in 1993. Infact, the aircraft involved, a Boeing 747-100 freighter re g i s t e re din Germany, did not crash as reported but experienced sub-stantial damage following a take-off incident at Doha, Qatar on4 July 1993. According to a report filed with ICAO by Germany,c a rgo pallets that shifted during the airc r a f t ’s take-off run atDoha caused substantial damage to the rear pre s s u re bulkheadand failure of the pressurization system. ■

TECHNICAL COOPERAT I O NSixty-five participants from 24 States of the Americas,Africa and Europe participated in a seminar on technicalcooperation matters at ICAO headquarters, Montreal, fro m2 to 6 April 2001. The seminar included presentations onwork flo w, activities in the field and project coord i n a t i o n .

37NUMBER 3, 2001

avoid” applications and pro c e d u res based on the use of ADS-B,t r a ffic information serv i c e - b roadcast and CDTI, to improve themixed operation of IFR and VFR traffic (helicopters and gener-al aviation aircraft). The main objective is improved safety butalso possible increase of capacity. DGAC/Sofreavia leads thet e a m .

In addition to the seven tiger teams, numerous activities areunder way in dif f e rent areas of Europe. A review of the signifi-cant developments follows.

Modified ADS. The development of the satellite- and AT N -based modified ADS (M-ADS) application in Norwegian air-space had been launched initially to enhance the provision of aflight information service and alerting service for helicopteroperations in the North Sea. The term “modified” was usedbecause of the utilization of the SSR transponder code in theADS messages in lieu of the aircraft identification. Positioni n f o rmation is transmitted to the Stavanger, Trondhiem andBodø ATC centres. The Kongsberg Co. is now extending thep roject to include M-ADS as well as ADS-B based on VDLMode 4 (i.e. combining the traditional ADS over ATN withADS-B in the same system). Testing of this implementation isincluded in the EC-sponsored downlinking of aircraft derivedi n f o rmation Phase II (DADI2) programme. Norway is one ofthe new countries to participate in NUP Phase II.

M e d i t e rranean free flight project (MFF). Another pro j e c ts p o n s o red by the European Commission and building on VDLMode 4 ground and aircraft infrastru c t u re, MFF will investi-gate, simulate and ultimately implement airborne traffic situa-

European ATM projects continued from page 8

be maintained when weather conditions are close to minimumfor VMC approach and, after further developments, belowVMC values.

Tiger Team Paris. This team is looking into the use of ADS-Bto improve safety and efficiency of operations on the airports u rface, especially during reduced visibility conditions, in sup-p o rt of an advanced surface movements guidance and contro lsystem (A-SMGCS). The work, whose application is known ass u rface enhanced visual acquisition (SEVA), also involves air-p o rt ground vehicles. The DGAC and Sofreavia lead the team.

Tiger Team Reykjavik. This team’s task is to look into ADS-Bbased ASAS applications in the non-radar environment of Nort hAtlantic airspace. The Icelandic CAA leads the team togetherwith airlines from both Europe and Canada, bringing the expe-riences from two continents together. The intention is tod e c rease the separation between aircraft by up to 50 perc e n t b yusing station-keeping pro c e d u re s .

Tiger Team Maastricht. In cooperation with the Euro c o n t ro lADS programme and Maastricht upper area control centre, thisteam will explore the potential benefits of ADS-B in high-densi-ty airspace with a well-developed SSR Mode-S infrastru c t u reand relatively advanced level of ATC automation. The main goalis to investigate possibilities to share the workload betweenATC and the cockpit.

Tiger Team Nice. The Nice team is developing “see and

nomic benefits and cer tification re q u i rements in order toenable more autonomous aircraft operation in the Euro p e a nATM system. To gain early benefits, there must be a capabilityto install improved equipment in existing aircraft. The MA-A FAS project there f o re is focusing on aircraft re t rofit, whileA FAS focuses on arc h i t e c t u res in new aircraft. The FMS studycited above is a part of the AFAS pro j e c t .

S i m u l a t i o n s . Simulations are one of the key tools used indeveloping new operational environments. Following the suc-cessful simulation of station-keeping at Malmö in May 2000, fullADS and data link capability is being implemented thro u g hS M A RT, an advanced multirole ATM re s e a rch and training sim-ulator located at the Swedish ATC Academy. This facility pro-vides a fully simulated ATC environment featuring up to 500simultaneous flights. With SMART, ATC operators are able towork in a modern ATM environment that provides possibilitiesto develop, test and verify new ATM applications and opera-tional pro c e d u res. At a later stage it will be possible to connectS M A RT to flight simulators so controllers and pilots will belinked in the same simulated ATM environment. This will pro-vide re s e a rchers with unique opportunities when developingnew ATM functions and operational pro c e d u re s .

Russian Federation. Russia’s Federal Service for AirTr a n s p o rt (FSAT) signed an order in 1999 approving the imple-mentation of an ADS-B system for civil aviation based on VDLMode 4. The order demands that the Russian ADS-B systembecome fully operational by the beginning of October 2005 inthe Tyumen region, between the Ural Mountains and Siberia,an area which is equal in size to France, Germ a n y, Italy and theUnited Kingdom combined. The regional ATC authority,Ty u m e n c o n t rol, oversees the air routes across this terr i t o ry.

The system installation will cover both en-route and term i n a lairspace as well as five of the major airports in the region, andan A-SMGCS system based on ADS-B will be installed atSamara International Airport. It is expected that the Russianc e rtification authority, MAK, will approve these installationsb e f o re 2002. Plans are available for an expanded infrastru c t u rea c ross the whole country.

The Russian State Research Institute for Aviation Systems(GosNIIAS) is conducting extensive activities in support ofADS-B implementation in the Russian Federation.

Activities in Sweden. L u f t f a r tsverket, the Swedish civil avia-tion administration, has embarked on a three-year implementa-tion programme of VDL Mode 4 based ADS-B starting at Kiru n aA i r p o rt, the nort h e rn-most airport in Sweden. Currently ATC isapplied through procedural control in this sparsely populatedand mountainous area, which is served by a limited number ofa i rcraft, often operating VFR. Scheduled services are conduct-ed with a limited number of individual airc r a f t .

Unmanned aerial vehicles (UAV) tested in this remote area willbe equipped with ADS-B. Because of the climate, aircraft manu-f a c t u rers often use the airport for cold-weather testing of new air-craft. It is expected that these “visiting” aircraft can easily beequipped with VDL Mode 4 equipment. New surveillance capa-bilities through ADS-B will provide a considerable safety enhance-ment and excellent support for search and rescue operations.

At Stockholm Arlanda Airport a new surveillance system is

tional awareness (AT S AW) and ASAS applications and fre eflight in a live traffic environment in the Mediterranean are a .The project is led by Ente Nazionale de Assistenza al Vo l o( E N AV), the Italian government agency for air traffic and aero-nautical services. Partners include civil aviation administrationsand re s e a rch organizations from France, Spain, Greece, Maltaand Sweden.

MFF is based on updated infrastru c t u re established thro u g hthe FA R AWAY projects. The objective of these EC-sponsored pro j-ects was to investigate the enhanced operational perf o rmance ofg round surveillance and aircraft navigation made possible thro u g hthe fusion of radar and ADS-B data. The project involved AT Ms e rvice providers and airlines in Italy, Germany and Sweden. Afollow-on project focused on extending the ground infrastru c t u reto give complete ADS-B coverage in Italian airspace.

S o u t h e rn ring air routes phase II project. This project is a partof the European Commission support given to republics of thef o rmer Soviet Union and Mongolia since 1991. It promotes thesafe and ef ficient operation of aircraft in the countries ofA rmenia, Azerbaijan, Georgia, Kazakhstan, Kyrgystan, Moldovia,Mongolia, Tajikistan, Turkmenistan and Uzbekistan. A nadvanced demonstration of ADS-B was held in Tblisi, Georg i aand Baku, Azerbaijan. The European Commission is curre n t l yconsidering a third phase.

Autonomous aircraft in future ATM system (MA-AFAS andA FA S ) . These two EC-sponsored projects are selecting and val-idating key airborne elements of CNS and defining their eco-

ICAO JOURNAL38

NAV CANADA , in partnership with ICAO, will host the prestigiousI n t e rnational Oceanic Conference 2001 in Banff, Alberta, Canada.The IOC conference is an annual event aimed at providing a foru mfor ANS service providers, aviation and airline org a n i z a t i o n s ,re g u l ators and industry to address oceanic airspace issues.

This year’s theme, “Improving Customer Service Through AdvancedTe c h n o l o g y,” will showcase leading edge keynote speakers, exhibits,technology presentations and panel discussions. Over 300 delegatesfrom around the world are expected to attend the three-day c o n f-e rence, making it an excellent forum for cooperative eff o rt andconsultation on all aspects of oceanic air operations.

The Banff Springs Hotel, in the picturesque mountain re s o rt ofB a n ff, Alberta, will be the site of IOC 2001. This World HeritageSite combines wild alpine beauty with first-class amenities for itsvisitors. Banff is accessible from the Calgary International Airportvia rental car or shuttle bus/limousine.

Plan now to attend this important conference in one of the most sce-nic areas of Canada and the world. The conference programme, withits knowledgeable speakers and international delegates, will ensurethat IOC 2001 is the most rewarding and productive event that youattend this year.

For more information on the conference and how to register,contact the ICAO European and North Atlantic Office

at ICAOEURNAT@Paris.ICAO.int or visit the NAV CANADA conference website at www.navcanada.ca/ioc2001.

INTERNATIONAL OCEANICCONFERENCE (IOC) 2001

October 2-5, 2 0 0 1

advantage of satellite technology, where available, as well asother possible alternatives.

The new polar routes create an opportunity to change thenature of air travel between the continents through shortertravel times resulting from direct flights between city pairs, andalso make it possible to develop new city pairs that can beserved by the next generation of aircraft. The potential of thenew routes will be realized provided that the appro p r i a t eresources are put in place to ensure that the route capacity with-in the Russian airspace will meet the forecast demand.

Nav Canada will accommodate the forecast traffic demandt h rough equipment enhancements at the Edmonton ACC,which has been fitted with a northern airspace display system(NADS) that has ADS and CPDLC capability. ■

Accident report continued from page 33

indication systems probes and wires in Boeing 747s equippedwith systems other than Honeywell Series 1-3 probes and com-pensators and in other model aircraft that are used in Title 14Code of Federal Regulations Part 121 service to determinewhether potential fuel tank ignition sources exist that are simi-lar to those found in the 747. The survey should include remov-ing wires from fuel probes and examining the wires for damage.Repair or replacement procedures for any damaged wires thatare found should be developed.

being installed for surface surveillance. ADS-B will be one ofthe surveillance data sources processed by the system and pre-sented to the operators.

In recent years, ADS-B has been used to improve the eff i-ciency of the snow removal process, especially during low visi-bility situations when the control tower would otherwise havelimited information about the position of the snow-clearingvehicles and the pro g ress of the operation. Full control of vehi-cle positions allows significantly improved timing of theresumption of take-off and landing operations, and hencei n c reased airport capacity.

The technical ATC systems in Sweden are in the process ofbeing replaced. Input of ADS-B data is part of the early modifi-cations planned for the new systems.

The way ahead. Among the factors that could slow downe ff o rts by the aviation community to take advantage of thecapabilities off e red by new technological systems are frag-mented solutions, incompatibility between airborne andg round-based systems, lack of operational pro c e d u res andincompatibility with the legal framework.

Several important elements are still missing before a fullydeveloped ATM system based on advanced CNS technologies isoperationally available and generating all of the anticipated ben-e fits. What is needed is a flexible and adaptable operational con-cept supported by appropriate operating pro c e d u res and legalframework as well as acceptance by all those involved — thepilots, controllers, service providers, operators and authorities.A safe system can be developed and implemented only if thereis confidence and trust.

The realization of ICAO’s CNS/ATM concept into an opera-tional environment is an iterative process. New elements will bei n t roduced gradually. Components, elements and pro c e d u res willcontinue to evolve as the re q u i rements change. Established stan-d a rds will be modified. The iteration will continue until it is timeto replace the “new” system with an even newer system. ■

Polar routes continued from page 22

frequency (VHF) coverage, are through HF voice in the north-ern part of Canadian airspace, the Reykjavik FIR and in theoceanic and northern continental areas of the Russian airspace.The effect of ionospheric disturbances in the polar area candecrease the availability of useable HF frequencies, a factorwhich is taken into account in determining route capacity.

The polar route capacity within Russian airspace is currentlylimited to one aircraft every 30 minutes on each route at eachavailable altitude at specified times predicated by communica-tions capability and the availability of English-speaking con-trollers. Before capacity can grow, more English-speaking con-trollers are needed as well as improvements in both communi-cations and flight data processing and display systems in theRussian ACCs.

Aside from looking at options for improving HF voice com-munications, emphasis will be placed on the use of HF data linkin support of ADS and CPDLC. There is also a need to improveg ro u n d - g round communications between ACCs by taking

39NUMBER 3, 2001

N EW PUBL I CAT I O N SFROM ICA O

ICAO’s Policies on Charges for Airports and Air Navigation Services (Document 9082)6th edition, 2001; 32 pagesAvailable in Arabic, English, French and SpanishOrder No. 9082...$10

Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services (Document 8585)116th edition, March 2001; 244 pagesPublished in English, French, Russian and SpanishOrder No. 8585/116...$65

Manual of Aircraft Ground De-icing/Anti-icingOperations (Document 9640)2nd edition, 2000; 37 pagesAvailable in English, French, Russian and SpanishOrder No. 9640...$11

Digest of Statistics No. 478Traffic-Commercial air carriers, 1995-1999Series T-No. 59; 371 pagesPublished in English, French, Russian and SpanishOrder No. DIG478...$122

Aeronautical Information Services Provided by States (Document 7383)89th edition, April 2001; 136 pagesPublished in English, French, Russian and SpanishOrder No. 7383/89...$38

CD-ROM Manual of Airport and Air Navigation Facility Tariffs (Document 7100)This CD-ROM incorporates the 2000 edition of the Manual of Airport and Air Navigation Facility Tariffs(Document 7100) published by ICAO.Published in English, French, Russian and SpanishOrder No. 7100-CD...$250

Airport Characteristics Data Bank (ACDB)2001 edition, six volumes (1,802 pages)Published in English, French, Russian and SpanishOrder No. 175022 (all volumes)...$487Note: Volumes covering different geographic regions may be acquired sepa-rately, however, the explanation contained in Volume 1 is necessary for under-standing content in other volumes. The ACDB is also available on diskette(ASCII format); the price for all data (Order No. ACDB-D) is $487 and forextracts (Runway Characteristics, Order No. ACDB-R; Taxiways, Order No.ACDB-T; Obstacles, Order No. ACDB-O) is $200 each.

Location Indicators (Document 7910)99th edition, January 2001; 192 pagesPublished in English, French, Russian and SpanishOrder No. 7910/99...$49

Technical Instructions for the Safe Transport ofDangerous Goods by Air, 2001-2002 Edition(Document 9284)2001; 688 pagesAvailable in English, French, Russian and SpanishOrder No. 9284...$88

The World of Civil Aviation, 1999-2002 (Circular 279)2000; 142 pagesAvailable in Arabic, English, French, Russian, and SpanishOrder No. CIR279...$50

Digest of Statistics No. 483Financial data-commercial air carriers, 1999.Series F-No. 53; 491 pagesPublished in English, French, Russian and SpanishOrder No. DIG483...$161

Regional Differences in International AirlineOperating Economics, 1997 (Circular 280)2000; 56 pagesAvailable in English, French, Russian and SpanishOrder No. CIR280...$18

Convention on International Civil Aviation (Document 7300)8th edition, 2000; 111 pagesPublished in English, French, Russian and SpanishOrder No. 7300...$29

Handbook on the International Airways VolcanoWatch (IAVW). (Document 9766)1st edition, 2000; 125 pagesAvailable in English, French, Russian and SpanishOrder No. 9766...$32

Digest of Statistics No. 480On-flight origin and destinationYear and quarter ending 30 September 1999Series OFOD-No. 91; 151 pagesPublished in English, French, Russian and SpanishOrder No. DIG480...$60

To order documents or obtain a complete list of ICAO publications and audio-visual training aids, contact:

Document Sales Unit, International Civil Aviation Organization, 999 University St., Montreal, Quebec, Canada H3C 5H7Telephone: 514-954-8022 • Facsimile: 514-954-6769 • Sitatex: YULADYA • E-mail: sales_unit@icao.int

The 2001 edition of the Catalogue of ICAO Publications and Audio-Visual Training Aids

can be found at ICAO’s website (http://www.icao.int)

41NUMBER 3, 2001

Language proficiency continued from page 26

need for reliable testing methods. Although there are manyc o m m e rcially available general English tests, few aviation-spe-cific English tests are widely available. The study group is eval-uating various English proficiency tests to determine theira p p ropriateness for aviation and eventually will propose amend-ments to the ICAO pro v i s i o n s .

The potential consequences of communication errors areserious enough that the matter of language pro ficiency must bea d d ressed. Half-measures would be inappropriate; rather, thebenefits in improved operational safety and ef ficiency arisingf rom a common language for ATC communications is a moti-vation for the aviation community to explore ways to achieveuniversal English language pro f i c i e n c y.

I n t e rnational civil aviation has a long history of cooperation.It is precisely this spirit which must be tapped into once again inthe search for solutions to the worldwide need for communica-tion pro f i c i e n c y. ■

S e a rch and rescue continued from page 29s t a ff. This needs to be understood in the context of the capaci-ties and limitations of human perf o rmance. In complex andintegrated systems, human perf o rmance is limited by two mainfactors: the functionality of the machinery and the functionalcapacity of the human. Managers need to be aware of these lim-itations and compensate for them.

With the essential principles of organizational change inplace and, in part i c u l a r, an active re g a rd for the human-at-the-c e n t re, States can expect to realize the maximum benefits oft e c h n o l o g y. In an environment of manageable risk, operationalincidents arising from both technical malfunctioning andhuman error can be minimized. States can anticipate both gre a tgains in operational regularity and economy and, with the inputof a highly functional SAR system, the safety and ef f i c i e n c yessential to the world community. ■

•Require research into copper-sulfide deposits on fuel quantityindication system parts in fuel tanks to determine the levels ofdeposits that may be hazardous, how to inspect and clean thedeposits, and when to replace the components.• R e q u i re in Boeing 747 aircraft, and in other aircraft with fuelquantity indication system wire installations that are co-ro u t e dwith wires that may be powered, the physical separation and elec-trical shielding of FQIS wires to the maximum extent possible.• R e q u i re, in all applicable transport aircraft fuel tanks, surge pro-tection systems to prevent electrical power surges from enteringfuel tanks through fuel quantity indication system wires. ■

New technology continued from page 20

The new technology utilized by Nav Canada is comprised oftwo key components: controller-pilot data link communications(CPDLC) and automatic dependent surveillance (ADS), bothusing satellite communications. CPDLC provides direct com-munication in areas where line-of-sight communication is notpossible, while ADS permits surveillance of aircraft that arebeyond line-of-sight range of radar systems without the needfor pilot interaction.

The combination of these capabilities is expected to pro v i d eair traffic controllers with significant improvements in eff i-ciency and effectiveness over the current system, which useshigh f requency (HF) radio. The technology will also helpNav Canada to control large amounts of airspace more safelyand eff e c t i v e l y, par ticularly in trans-oceanic areas and inCanada’s far north. (In addition to implementing advancedt e c h n o l o g y, Nav Canada is in the process of installing newradar sites across the far north. Four sites are under con-s t ruction and it is likely additional sites will be announced inthe coming year. )

During the flight of COA99 on 1 March, CPDLC communica-tions took place between the aircraft and Nav Canada’s technicalsystems centre located in Ottawa. The ADS connection with thea i rcraft was interrupted while it was flying over the pole becauseof the lack of satellite coverage in the far north. Future imple-mentation of airborne and ground-based data communicationstechnology will help provide the necessary coverage for this are a .

ADS has already had an impact on transatlantic operations.Its introduction over the North Atlantic is reducing reliance onHF communications, and it is anticipated that CPDLC willreduce the remaining portion of routine HF communication. Atp resent 18 per cent of the 1,000 aircraft flying the Nort hAtlantic each day are equipped for ADS and CPDLC.

N o rth Atlantic trials of ADS capabilities began in mid-1999, withp a rticipation from eight airlines. ADS waypoint position re p o rt i n gwent into full operation in the Gander and Shanwick FIRs on 29J a n u a ry 2001, meaning that aircraft which use ADS are no longerre q u i red to provide position updates via voice communications.

Nav Canada is working with the United Kingdom’s NationalAir Tr a ffic Services (NATS) to investigate the practicality ofdeploying CPDLC technology in the Shanwick (EasternAtlantic) FIR. The first U.K. CPDLC contact was establishedwith Continental COA99 on 6 Marc h . ■

I N T E R N AT I O N A L M E E T I N G S

North Atlantic Systems Planning Group (NAT SPG/37) 12-14 June 2001, Paris

Working Group of the Whole of the Operations Panel(OPSP) 26-29 June 2001, Montreal*

Africa-Indian Ocean Planning and ImplementationRegional Group (APIRG/13)25-29 June 2001, Sal Island, Cape Verde

Asia/Pacific Air Navigation Planning andImplementation Regional Group (APANPIRG/12)20-24 August 2001, Bangkok

33rd Session of the ICAO Assembly (A33)25 September - 5 October 2001, Montreal

*dates to be confirmed

ICAO JOURNAL42

Capstone initiative continued from page 18

some of this spectral “real estate” must be freed up by coordi-nating a permanent spectrum assignment as part of the standards process. The industry standards process is nowunder way, with the recent creation of an RTCA working grouptasked with the development of a MOPS document for the UAT.

Capstone will begin working in the terrain-constrained area ofsouth-east Alaska in early 2001 to improve safety and access tothat area using lessons learned from the tests performed atBethel, as well as incorporating other technologies to improvesurveillance and navigation capability. Additionally, the workprogramme will include demonstrating technology aimed atreducing runway incursions. ■

Data link simulations continued from page 13

f e a t u re of partial ACM be retained rather than the monitoringRTF indication given when full ACM is used.

The participants also stated that the FLIPCY service off e re da safety benefit as it provides early warning of discrepancies inro u t i n g s .

S u m m a ry. The NATS simulations have shown that the com-bination of data link services generally resulted in a decrease inc o n t roller workload. When simulated individually, the flight planconsistency service resulted in the largest workload re d u c t i o n .

The introduction of data link services in the simulation exer-cises resulted in less time spent communicating via radiotele-p h o n y. This reduction was greatest when the implemented datalink services were used in combination.

The par ticipating controllers expressed concern about theresponse times involved in some data link communications. Forinstance, the average time taken by flight crews to respond toan ACM instruction to change frequency ranged from 40 to 105seconds, while the response via radiotelephony is virt u a l l yinstantaneous. The controllers indicated that they felt a changein culture on the flight deck would be necessary before pilotswould react to data link messages as quickly as they do to voicei n s t ru c t i o n s .

Despite the concern about potential delays in crew re s p o n s etimes, the participating controllers stated that the data links e rvices simulated would be suitable for perf o rming “house-keeping” tasks. They also concluded that potential safety bene-fits were off e red by the data link services, and pointed out thatthe introduction of data link may re q u i re changes to the ro l e sand responsibilities assumed by operational staff .

Feedback from the participants indicates that they would likethe FLIPCY service to evolve into a controller tool that not onlydetects discrepancies in aircraft routes but also enables the dis-c repancies to be resolved. This could be achieved by pro v i d i n gthe ability to uplink the ground system route to the airc r a f t .This recommendation has been relayed to the Euro c o n t ro lg roup responsible for the operational definition of initial air-g round data link communications — ODIAC — which initiallydefined the services implemented by EOLIA. ■

P romoting the Development of I n t e rnational Civil Av i a t i o nThe International Civil AviationOrganization, created in 1944 to promotethe safe and orderly development of civilaviation worldwide, is a specialized agency ofthe United Nations. Headquart e red in Montre a l,ICAO develops international air transport stan-dards and regulations and serves as the medium for cooperation in all fields of civil aviation among its 187 Contracting States.

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