Communications Facilities, Procedures and PhraseologyCommunications facilities utilized by Air Traffic Services (and these may vary with the characteristics of the sectorentered by aircraft) are either recorded or reported in listening logs by the services concerned. However, the Air TrafficService investigation must not overlook the possibility of obtaining further communications evidence from other sourcessuch as the aircraft flight data and cockpit voice recorders, other aircraft whether on the ground or in-flight and/or othercivil or and/or military ground stations listening on the same frequency(ies). Furthermore, when appropriate, all voice anddata link communications on the operator’s communication network should also be investigated including commercialproviders of aeronautical communications information.

• With either kind, simultaneous multi-track recorders allow for the input of synchronized time signals in any of a number of forms (hook-up with a talking clock provided as an accessory to the recording machine or for other purposes: coded or plain language time signals). This provides an exact chronological reference datum as the recordings on the different tracks are naturally synchronized. National regulations governing the preservation of such recordings vary somewhat, the minimum period being in the order of 30 days.

• Where such recordings exist, they represent a very important source of information for the Air Traffic Service investigation. The read-outs are as a rule fairly easy but call for certain essential precautions:

• a) extreme care must he exercised in handling and storing master records (the risk of deterioration or obliteration must always be borne in mind)

• b) a wise precaution is to make, wherever possible, one or more copies of the master record and to use these copies for most of the playbacks when it is not essential to use the original recording

• c) in reconstructing the timing for all documentation, the same reference datum must naturally be used throughout, and the Air Traffic Service investigation will therefore be responsible for fixing the datum point and establishing any differences between times quoted or used in the recordings from various sources

• d) it will be necessary to synchronize all communications recording time datum with that on the flight recorders from the aircraft. The transcripts of the readouts are likely to be used by persons who have not listened to the tapes which, moreover, may come from various air traffic service centres and/or units; certain specific data should therefore be provided with each transcript and a uniform presentation should be adopted

• a) an introductory page should indicate the origin of the recording, the frequency or frequencies

• recorded, the period covered by the transcript, reason for making that transcript, person responsible for it and where and when it was made (possibly the location of the master records)

• b) each succeeding page may contain at least the following columns;

• i) time indications• ii) sending stations• iii) receiving stations• iv) material which was read-out without difficulty• v) doubtful or unintelligible material• vi) remarks of the person(s) responsible for the transcript.

• The Air Traffic Services investigation should also address and report upon all factual information relating to the operational status, performance and serviceability of the communications facilities, including standard operating communications procedures and phraseology for a period relevant to the occurrence. By carefully noting the quality of

• the communications, the Air Traffic Service investigation may make further analysis of the communications to determine other useful aspects for the investigation or forwarding to the Operations Group.

• Dependent upon the nature of the occurrence, some or all of the following items may be relevant to communications aspects:

• a) air-ground-air in use (VHF, UHF, HF, data link etc)• b) air-ground-air outlet sites, elevations, networks,

configuration aid coverage diagrams• c) terrestrial and satellite controlled

intercommunications• d) calibration of ATS equipment• e) frequencies and propagation characteristics• f) telephony and microphone techniques

• g) calling, replying and acknowledgment standard operating procedures

• h) unit/service identification• i) clear, unambiguous standard

operating procedural words, phrases and language used in communications

• j) readback/hearback errors or omissions

• Navigation• Where relevant the navigational aspects of an

investigation may be of concern to the Air Traffic Services investigation. The navigational capabilities or equipment notified as carried in the aircraft should be checked against the aircraft records. The navigation facilities may comprise terrestrial components such as NDBs, VOR, DME, ILS, LORAN, ATS surveillance systems equipment and space-based GNSS and its augmentation. The Air Traffic Service investigation should also investigate the navigational aspects of an occurrence involving aircraft equipped with sole-means global positioning sourced navigation systems.

• The following features should be considered in respect of each terrestrial navigation facility examined:

• a) location (geographic co-ordinates)• b) identification signal• c) power output and supply• e) emergency equipment - warning system(s)

recording of malfunction

• f) Equipment calibration and radiation pattern• g) Operating and maintenance schedules, and their

notification (AIP, NOTAMs)• h) Normal level of performance• i) Interference(s)• j) Past complaints, interruptions and failures (crew,

operation, etc.)• k) Statements from relevant personnel including

other aircrew who used these aids When navigation information is obtained

• Aerodrome Facilities• Where it is relevant to the particular occurrence,

the Air Traffic Services investigation may have to examine and verify the status of many aerodrome facilities used by or available to the aircraft involved in the occurrence. Amongst the items that may need to be checked and verified are the following:

• a) characteristics of the runway(s) in use• b) characteristics of the movement areas• c) surrounding terrain, obstructions and

meteorology characteristics• d) aerodrome diagrams

• e) lighting and guidance signage• f) electronic surface movement detection systems• g) standard, contingency and emergency operating

procedures• h) visual and electronic navigation aids• i) communications networks• j) environmental conditions• k) facility status register

• Aircraft Performance• The Air Traffic Services investigation should

establish, record and verify the accuracy of all information relevant to actual performance of the occurrence aircraft, in particular the flight planned performance should be compared to actual performance achieved. Valuable information may be derived from recorded data, observations, photographs, eyewitnesses, or from other air traffic services personnel or aircrew in the vicinity.

• The selection of data to be collected and reviewed will be dependent upon the circumstances of the occurrence being investigated. However, it is most desirable that the investigation examine the original rather than copies of the recorded

• data wherever possible. It may be necessary, in certain cases, to have the Operations Group examine the data from which Flight Manual performance is determined in order to establish its relevance to the particular circumstances.

• The Air Traffic Services investigation should establish, record and verify the accuracy of all information relevant to its activity in relation to the conformance of the flight. This may include determination of expected outcomes originating from any air traffic services control instruction, information or advice compared with the actual outcomes.

• Reconstruction of horizontal and vertical profiles of the flight by use of factual data may be a useful tool in determining the Air Traffic Service officer’s knowledge and expectation of the aircraft performance in the air traffic service system. For example, was the clearance instruction within the capability of the aircraft performance envelope, or was the aircraft directed towards hazardous weather or terrain etc. Dependent upon the nature of the occurrence, some or all of the following items may be relevant:

• a) knowledge of aircraft performance and limitations

• b) reconstruction of relevant flight profiles• c) flight plan validity and conformance• d) horizontal and vertical navigation• e) aircraft physical operating environment

emergency operations

• Standard Operating Procedures and Practices• Whilst it is not the function of an Air Traffic Services

investigator to become involved in the disciplinary aspects of the enforcement of regulations and instructions it is a necessary part of the investigation to establish whether the applicable directives, operating standards, procedures and practices were complied with. All relevant material should also be examined to establish whether, in the light of the occurrence, they were proper and adequate for ensuring safety of operations, and whether they were presented in a format easily understood.

• It may be necessary to also consider the safety lessons and preventative aspects of recommending a review of the existing directives, operating standards, procedures and practices or development of new material. In examining these matters it is important to distinguish between what material has mandatory effect and what is advisory

• Items that should be checked, and verified may comprise a combination of the following:

• a) National legislation• b) ICAO Annexes• c) ICAO Procedures for Air Navigation Services• d) air traffic services manuals and instruction

circulars• e) workstation/sector handbooks and/or

instructions• f) copies of any pertinent letters of agreement• g) map/chart of area of responsibility

• h) co-ordination requirements with other units• i) aeronautical information publications• j) applicable aircraft proximity standard/s• k) NOTAMs• l) flight progress preparation, processing and

displays• m) level change and non-standard flight levels

procedures• n) communications, navigation and surveillance

procedures

• QUIZ• Why determination of the precise time of the

occurrence is important. Please comment