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!

Thank you Questions?

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