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RAeS Workshop on Detect and Avoid
DAA standards development
Work in progress at EUROCAE WG73
Operational Services and Environment Definition (OSED) for
Traffic Awareness and Collision Avoidance in Class A, B and C Airspace under Instrument Flight Rules
TAACAS
Tony Henley
31st March 2015
Contents
• Responsibilities and the ‘Separator’
• Rules of the Air - No ATC clearance
• Rules of the Air – Under ATC instructions
• Focus of EUROCAE wg 73 - Class A, B and C airspace
• TAACAS Assumptions – Selected
• TAACAS Requirements – Selected
Disclaimer – the information presented with permission of but is not endorsed by EUROCAE Much of it is derived from the draft TAACAS OSED
Some of it is derived from THL lecture notes
TAACAS STATUS
TAACAS - Operational Scenario and Environment definition document
• Ready for release as Interim ED EUROCAE Document for community review
• Is it correct? Is it useful ?
• Work continues on the associated Safety Assessment
• May lead to specific safety requirements - although a conflicted topic
• Further work needed on Performance Requirements and Limitations
• E.g. minimum RPAS climb rate for acceptable operation!
• Use of lateral manoeuvres against VFR traffic
• TAACAS is a concept to meet the class A B and C requirements but
Will anyone build it?
Responsibilities
Strategic Conflict Management
• Airspace organization and management
• Demand and capacity balancing
• Traffic synchronization components
1
Separation Provision
Tactical process of keeping aircraft away from
hazards by at least the appropriate separation
minima
2
Collision Avoidance
Must activate when the separation has been
compromised
3
The Separator
In all situations, the entity responsible for separation (the
separator) must be known.
•2.7.18 The separator is the agent responsible for separation
provision for a conflict and can be either the airspace user or a
separation provision service provider.
•2.7.19 The separator must be defined (that is predetermined)
prior to the commencement of separation provision; however, the
role of separator may be delegated.
FAA, Aeronautical Information Manual – Official Guide to Basic Flight Information and ATC procedures – 2006
Rules of the Air
Extracts from ICAO Annex 2 Chapter 3.2
ROA 3.2 Avoidance of Collisions
Nothing in these rules shall relieve the pilot-in-command of an aircraft from the responsibility of taking such action, including collision avoidance manoeuvres based on resolution advisories provided by ACAS equipment, as will best avert collision.
Note 1. It is important that vigilance for the purpose of detecting potential collisions be not relaxed on board an aircraft in flight, regardless of the type of flight or the class of airspace in which the aircraft is operating, and while operating on the movement area of an aerodrome.
ROA 3.2.1 Proximity
An aircraft shall not be operated in such proximity to other aircraft as to create a collision hazard.
Right-of-way
ROA 3.2.2 Right-of-way
The aircraft that has the right-of-way shall maintain its heading and speed.
ROA 3.2.2.1 An aircraft that is obliged by the following rules to keep out of the way of another shall avoid passing over, under or in front of the other, unless it passes well clear and takes into account the effect of aircraft wake turbulence.
ROA 3.2.2.2 Approaching head-on. When two aircraft are approaching head-on or approximately so and there is danger of collision, each shall alter its heading to the right.
Priority
ROA 3.2.2.3 Converging. When two aircraft are converging at approximately the same level, the aircraft that has the other on its right shall give way, except as follows:
a) power-driven heavier-than-air aircraft shall give way to airships, gliders and balloons;
b) airships shall give way to gliders and balloons;
c) gliders shall give way to balloons;
d) power-driven aircraft shall give way to aircraft which are seen to be towing other aircraft or objects.
Overtaking
ROA 3.2.2.4 Overtaking. An overtaking aircraft is an aircraft that approaches another from the rear on a line forming an angle of less than 70 degrees with the plane of symmetry of the latter
i.e. is in such a position with reference to the other aircraft that at night it should be unable to see either of the aircraft’s left (port) or right (starboard) navigation lights.
An aircraft that is being overtaken has the right-of-way and the overtaking aircraft, whether climbing, descending or in horizontal flight, shall keep out of the way of the other aircraft by altering its heading to the right, and no subsequent change in the relative positions of the two aircraft shall absolve the overtaking aircraft from this obligation until it is entirely past and clear.
Geometry of Separation
When not provided by ATC-
UA as give way aircraft - Rules of the air
Intruder-
Right of way
aircraft
UA –Give way
Aircraft
110 deg
Overtaking
Zone
‘Head on or
approximately so’
zone (not precisely
defined )
Crossing
Zone
Right of way
zone
UA has responsibility for
separation for all cases
shown – shared with
Intruder for Head- On
case
Geometry of Separation
When not provided by ATC-
UA as Right of way aircraft - Rules of the air
Intruder–Give
way Aircraft
UA -Right of
way aircraft
110 deg
Overtaking
Zone
Crossing
Zone Give Way
Zone
UA has NO responsibility for
separation except with
respect to aircraft crossing
from the Give Way zone and
the Head on Zone
‘Head on or
approximately
so’ Zone
Intruder–Give
way Aircraft
RPA -Right of
way aircraft
Impact point
(predicted) Collision Boundary
Collision Threshold
Separation Boundary
Separation Threshold
Pilot initiated collision
manoeuvre
Why ROW aircraft
should
maintain heading
Operation under an ATC clearance
ROA 3.6.2.1 Except as provided for in 3.6.2.2 and 3.6.2.4, an aircraft shall adhere to the current flight plan or the applicable portion of a current flight plan submitted for a controlled flight unless a request for a change has been made and clearance obtained from the appropriate air traffic control unit, or unless an emergency situation arises which necessitates immediate action by the aircraft, in which event as soon as circumstances permit, after such emergency authority is exercised, the appropriate air traffic services unit shall be notified of the action taken and that this action has been taken under emergency authority.
( 3.6.2.2 relates to ‘Inadvertent changes’ from flight plan and 3.6.2.4 relates to ‘Weather deterioration below the VMC’.)
If an aircraft pilot believes that the ATC clearance he is flying will result will result in the aircraft being operated in such proximity to other aircraft as to create a collision hazard the pilot is expected to contact ATC for guidance
EUROCAE WG73 Approach
• A piece at a time – limited scenarios to enable early use
• Scenario 1 – enroute operation under IFR in class A, B and C airspace
• Detect and Avoid in Scenario 1- Assumptions
• RPA flying on a Cleared Flight Plan - Separation is provided by Air Traffic Control
• All aircraft (should be) cooperative (ie fitted with transponder)
• Most manned aircraft fitted with TCAS (Traffic Collision Avoidance System)
• In accordance with ICAO annex2 Rules of the air
• Aircraft following an ATC clearance can only maneuver in an emergency
• Should not maneuver to maintain ‘separation’ or to keep ‘well clear’
• Must take all necessary action to avoid a collision
Traffic Awareness And Collision Avoidance (TAACAS) Scope
Cooperative traffic threats
• When En-route under Instrument Flight Rules in A, B and C airspace.
• provision of traffic situation awareness information to the remote pilot
• provision of collision avoidance manoeuvre guidance to the remote pilot when collision risk is detected
• automatic collision avoidance manoeuvre in the event that the remote pilot does not respond in an appropriate time.
Non cooperative traffic threats
• When the RPAS is exceptionally operating in airspace where non cooperative VFR traffic is present
• ‘Some’ traffic awareness and collision avoidance capability
Out of scope
TAACAS does not provide specific guidance for ‘traffic avoidance’ ( self Separation) i.e. does not support ‘rules of the air’ separation or keeping ‘well clear’.
• These are not allowed in Class A, B or C Airspace
• When an aircraft is receiving a separation service it may not manoeuvre
• without an ATC clearance except in an emergency (such as the need to avoid a collision)
• to avoid hazardous weather.
Ref ICAO Annex 2
TAACAS does provide traffic information and Collision avoidance guidance to the remote pilot on all detected threats
Definition of terms
• En Route -From completion of Initial Climb through cruise altitude and completion of controlled descent to the Initial Approach Fix”
• In airspace class A, B and C, ATC is required to provide separation provision between all traffic, whether operating under Visual Flight Rules (VFR) and/ or Instrument Flight Rules (IFR).
• In emergency situations the RPA may have to transit through other airspace classes including F and G, where ATC is not responsible for separation provision. See ICAO Annex 11 on Air Traffic Service
• Cooperative intruders are defined as aircraft, proximate to the RPA, using avionics equipment that provides identification, position, or other data which can be detected by suitably equipped RPA
• Non-Cooperative intruders are defined as aircraft, proximate to the RPA, which do not provide data which can be detected by the RPA.
Why not use of TCAS?
• TCAS is designed to provide CA advice to a human pilot
• Initially pilot required to visually acquire the intruder before manoeuvring
• Since 2002 pilots are requirement to manoeuvre when an ‘RA’ is issued
• in 2009 EASA certified the A380 Auto-pilot /Flight director TCAS mode –the autopilot can now automatically conduct the correct TCAS manoeuvre
• However ICAO ACAS Manual Doc 9863 (2012 Edition) bars the use of ACAS on RPA For auto or manual collision avoidance or for situation awareness
• Reasons include
• Datalink availability and delays
• Limitations in the accuracy of the intruder position information
• The difficulty of certifying an automatic manoeuvre function
TAACAS Assumptions (Selected) –
Operation in Class A B and C airspace
A3 In the event that the remote pilot determines, from the information provided by TAACAS or other information, that a situation is developing such that in the near term proximity to another aircraft may create a collision hazard he/ she will have the option of contacting the relevant ATC sector controller for clarification and or a new clearance
A4 The remote pilot will respond to the CA guidance provided by the TAACAS and manoeuvre to avoid the collision. If possible he /she will contact ATC to inform them of the event in accordance with the standardised procedures for resolution advisory collision avoidance manoeuvres and reporting described in ICAO PANS-OPS Doc 8168 [Ref 19].
A5 In the event of an automatically initiated CA manoeuvre occurring the remote pilot is expected to allow it to continue to completion. However if the remote pilot believes that the TAACAS initiated manoeuvre is unnecessary or unsafe he/she can cancel the manoeuvre at any time,
TAACAS Assumptions (Selected) –
Operation in under VFR/ Outside of controlled airspce
A8 When exceptionally operating in Class D, E, F or G airspace In the event that the pilot determines, from the information provided by TAACAS or other information, that a situation is developing such that in the near term proximity to another aircraft may create a collision hazard he/ she may, If not flying on an ATC clearance, initiate a traffic avoidance manoeuvre if appropriate
A9 When exceptionally operating in Class D, E, F or G airspace the remote pilot will respond to the collision avoidance guidance provided and manoeuvre to avoid the collision
A10 When exceptionally operating in Class D, E, F or G In the event of an automatically initiated CA manoeuvre occurring the remote pilot is expected to allow it to continue to completion. However if the remote pilot has reason to believe that the TAACAS initiated manoeuvre is unnecessary or unsafe he/she can cancel the manoeuvre at ant time
C2 Link
A11 The RPAS C2 link will provide the Required Communication Performance (RCP) necessary to ensure that the remote pilot is able to initiate a manual collision avoidance manoeuvre in due time
A13 The RPAS operator will confirm with the appropriate regulator that the quality of service guarantees available for the C2 link are sufficient to support the requirements of the TAACAS
A17 In the event of a lost C2 link condition ATC should be informed, typically by use an appropriate SSR transponder code and is expected to keep other, known, traffic clear of the RPA
Additional Assumptions
A15 RPA will be required to carry a Mode S transponder. As a basic requirement for entry into Class A, B and C airspace . This is also necessary to inform TCAS equipped intruders that the RPA is CA equipped, to enable coordination.
A16 In addition to a Mode S transponder, the equipment specific by the local ATC authority for the airspace in which it will operate will also be carried.
A12 Remote pilots will be trained to understand the TAACAS modes and limitations, to operate the TAACAS and to respond appropriately to the information it provides
WG 73 approach – work in progress
Traffic Awareness and Collision Avoidance System (TAACAS)
• Requirements (selected)
1/7 TAACAS shall detect and track proximate traffic and provide traffic situation information to the remote pilot
2/8 The TAACAS shall, in the event that a collision hazard exists, provide a specific alert to the remote pilot together with appropriate manoeuvre guidance to assist the pilot in avoiding a collision
3/9 The TAACAS shall, in the event that an immediate collision hazard exists and there is insufficient time for the pilot to initiate a manoeuvre , automatically initiate an appropriate collision avoidance manoeuvre. (Informing both pilot and ATC if possible)
4/10 The TAACAS, following initiation of a collision avoidance manoeuvre (automatic or pilot initiated), shall on command from the pilot terminate the manoeuvre
Additional requirements
11. Full TAACAS collision avoidance shall be provided against - non cooperative intruders, with speeds at least up to 250kt and size 1 sq m (which are not designed to be stealthy) when in Class A, B or C airspace, - and cooperative intruders with speeds of up to 600 knots
R19 TAACAS shall include a Mode S 1030 MHz interrogator
R20 In encounters with aircraft equipped with collision avoidance systems, collision avoidance alerts shall be coordinated with the threat using the coordination protocols and messages specified in ED 143 (TCAS 2 MOPS).
R21 In the event that the C2 data link is not available the TAACAS shall provide automatic collision avoidance manoeuvres when necessary to avert a collision.
Implications and potential safety argument
• TCAS is not used stand alone – it is aided by non cooperative sensors.
• Good (better than TCAS) situation awareness is provided to the remote pilot to compensate for the lack of the ‘See’ element of ‘see and avoid’
• The pilot has the information to assess any TAACAS proposed avoidance manoeuvre and decide to execute it manually –typically manoeuvres will occur earlier than a conventional TCAS RA alert ( but are not ‘Separation’
• In the event that the pilot does not respond in time (or the datalink is not available) as a last resort the TAACAS will initiate an automatic manoeuvre.
• All manoeuvres will be coordinated with manoeuvres initiated by the intruder aircraft (if it is equipped with a CA functions) but
• TAACAS will not wait for a TCAS equipped aircraft to react first –it may not!
Certification strategy
• Today
• There is no target level of safety for manned collision avoidance – there is an achieved figure that must not be degraded.
• In A, B and C airspace IFR collision avoidance is largely achieved by ATC maintaining good separation between aircraft.
• Manned aircraft pilots are expected to detect non-cooperative intruders based on ATC traffic report ( if available) and their own eyes
• Automatic TCAS manoeuvre execution is now allowed (with conditions)
• With TAACAS
• The RP potentially has more accurate and complete information to support manually initiated avoidance manoeuvres as the primary mode with automatic backup when the link is not available
Important Terms - aircraft including RPA
VMC/ IMC
Visual Meteorological Conditions
good visibility and well clear of clouds )
Instrument Meteorological Conditions
poor visibility or near to clouds
VFR/ IFR
Visual Flight rules – only possible in VMC
Instrument Flight Rules –
possible in VMC and IMC usually under Air Traffic Control
IFR and VFR (basic)
Instrument Flying Rules IFR in Airspace A – C
• Flight in any visibility conditions, VMC or IMC
• ATC provides separation
• Aircraft constrained to follow ‘cleared’ flight plan or ATC instructions
• Aircraft cannot maneuver independently except to avoid a collision
Visual Flight Rules VFR in Airspace D – G
• Only possible in good visibility, VMC
• ATC does not provide ‘Separation’, may provide traffic information
• Pilot is responsible for ‘separation’
• Can maneuver at will providing
• Does not enter airspace A or B
• Will not be perceived as a Hazard by other airspace users
IFR and VFR
Operation under Visual Flight Rules, VFR also allowed in B and C
• Only possible in good visibility , VMC
• ATC provides ‘Separation’ from all traffic in Class B • but only from IFR traffic in class C
• Pilot is responsible for ‘separation’ from VFR traffic in class C
• In class B constrained to follow flight plan /ATC instructions
Operation under Instrument Flying Rules, IFR also allowed in Airspace D -E
• ATC provides ‘Separation’ from other IFR traffic • But information only on VFR traffic
• Aircraft constrained to follow flight plan /ATC instructions • cannot maneuver independently except to avoid a collision
Separation Responsibility
The separation assurance and responsibilities depend on the class of airspace, and on the flight rules under which the aircraft is flying.
Box marked “ATC” : ATC is responsible for the separation provision
Box marked “UASATC“: the pilot is responsible for the separation provision with the help of Traffic information (from a Flight Information Service);
Box marked “UAS”: the pilot is responsible for the separation provision (but may be no FIS).
Collision avoidance is always the responsibility of the Pilot
ALL
collision avoidance
VFR/VFR
separation
IFR/VFR
separation
IFR/IFR
separation
ALL
collision avoidance
VFR/VFR
separation
IFR/VFR
separation
IFR/IFR
separation
A B C D
ATC ATC ATC
ATC
ATC ATC
ATC
ATC
Controlled AS
E F G
Uncontrolled AS
UASATC UASUASUAS
UASUAS
UAS
UASUASUASUASUASUASUAS
UASATC
UASATC
UASATCUASATC
UASATCUASATC
Airspaceclasses
Types
offligh
t
USA Airspace structure
http://www.atlasaviation.com/AviationLibrary/usairspaceclasses/usairspaceclasses.htm#classes
FL or Alt Band
Albania Armenia Austria Azerbaijan Belgium/Lu
x Bosnia H'zina
Bulgaria Croatia Cyprus Czech Rep
Denmark Estonia Finland
Up Limit CAS 660 460 660 460 660 410 660 660 460 660 660 660 660
245-460
205-245
195-205
C C C C C C
150-195
130*-150
C
D
C
95*-130*
C C C
C C
3K*-95* E
C
E D E
E
SFC-3K*
G
G
G
G G
G
G
G
G
G G
G
G G
Major TMA C C C C
Minor TMA E
D No TMAs
D D D C D
CTA/Awy C C D E
C C above 100 C D
200 ^
up to 195
C D E C D D
CTR* D
C
D E
C D D
C
D B
ATZ C D D G* C D G* C D G*
FL or Alt Band
France/ Monaco
FYROM Germany Georgia Greece Hungary Ireland Italy Latvia Lithuania Malta Moldova Netherlands
Up Limit CAS 660 660 660 460 460 660 660 460 446060 660 460 660 660
245-460
205-245
195-205
C C A C C C C
150-195
130*-150 D
C
95*-130*
D
C E
C
C C A from 285
C C
3K*-95* E E F
C
A B
SFC-3K*
G
G G G
G G
G
G G
G C
G G
Major TMA A D C A E A
Minor TMA C D E E C D
B E
CTA/Awy D E D E C D E D E
D A
CTR* A
D D D F
C C C
A C D
C
C D
C C
C
FL or Alt Band Norway Poland Portugal Romania Slovak Rep Slovenia Spain Sweden Switzerland Turkey Ukraine UK Serbia &
Montenegro
Up Limit CAS 660 460 660 660 660 660 460 460l 660 660l 660 660
245-460
205-245
195-205
C C C C C C
C
150-195 C D
130*-150
C
C D E
95*-130*
D G
C C
D
C G C E
C
3K*-95*
C
E E D
SFC-3K* G G
G
G G G
G
G G
G
G
Major TMA C A C A D E
Minor TMA D A C D E
D D C D
E
CTA/Awy E C
C D
A C C A C D F
CTR* D
G*
C
C C
C D D D
E
C
D
C D A D E