Do you expect pilots to follow RAs?

[ferris]

Debate at work about whether a pilot should follow an ATC instruction or an RA.

1. What do your books (MATS, AIP etc) say?

2. What do you believe the pilot would do?

3. If the pilot follows the RA in contravention of the instruction, is he legally justified? (ie. in keeping his responsibilty for the safety of his aircraft, can he legally ignore an instruction?)

Answers especially appreciated from UK controllers.

[ferris]

RAs= TCAS Resolution Advisory:confused: :rolleyes:

[Spitoon]

As far as I'm aware, in the UK pilots are trained to follow a TCAS RA regardless of any ATC instruction (because of the possible co-ordinated RAs presented to the pilots).

The words from the MATS Part 1 (http://www.caa.co.uk/docs/33/CAP493__Part1.pdf) (SI 3/01) are

Effect on ATC Operations
The effect of advisories on air traffic control operations is as follows:
Traffic Advisory - Pilots are advised not to take avoiding action on the basis of TA information alone but may ask for traffic information.
Resolution Advisory - Pilots are expected to respond immediately but have been instructed to restrict manoeuvres to the minimum necessary to resolve the confliction, advise the air traffic control unit as soon as is practical thereafter and return to their original flight path as soon as it is safe to do so.

and

Departure from ATC Clearance
The commander of an aircraft is permitted to deviate from an air traffic control
clearance for the purposes of avoiding immediate danger [Air Navigation Order 2000, Article 84(3)(a)]. Response to a Resolution Advisory comes under this heading and is not, therefore, a breach of Rule 31(3)(a) which requires conformity with the clearance. The commander is required to notify the air traffic control unit as soon as possible (Rule 31(4)) and submit a written report within 10 days (Article 84(4)).

AIC 124/98 (http://www.ais.org.uk/Uk_aip/AIP/pdf/aic/4Y308.PDF) also covers the topic.

[5milesbaby]

our new training for emergency procedures (inc. Avoiding Action) states that pilots will ALWAYS follow the onboard computer if a TCAS RA occurs, so action offered should be in the form of vectors, as altitude changes can become confusing, as in Germany. Therefore, yes we sould expect you to comply with TCAS RA's, just informing ATC of action taken. Be advised however, that by following a TCAS RA, separation responsibilities are immediately taken away from ATC until you report clear and happy to resume control. However, never take this to mean you should try to comply with ATC, TCAS is far more up-to-date due to our lengthy history updates.

[HEATHROW DIRECTOR]

As my colleagues have said, you to take your own action and let us know when you are returning to the cleared level. However if, as I have experienced several times, TCAS taking an aircraft into a highly dangerous situation, I would certainly tell you and offer avoiding advice. Whether you accepted would be up to you.

[Scott Voigt]

In the US the crews are supposed to follow the RA's. Tell ATC when they do it, and then we do nothing other than issue traffic advisories until the aircraft can return on their own to their assigned altitude...

regards

[fourthreethree]

My understanding of this is that it is a very grey area indeed. You are obviously referring to the tragic mid-air over Switzerland, where the Russian pilot apparently disregarded his TCAS RA in favour of the controller's repeated instructions to descend.
I may be mistaken here, but my belief is that the pilot in this case followed his company's policy, giving priority to the ATC clearance. Most companies tell their pilots to follow an RA regardless of ATC.

As an atco myself I have been involved in several cases whereby a pilot has reacted to an RA, mainly due to often military traffic climbing to a safe level beneath the aircraft in question, but with a very high roc, triggering the TCAS and effectively turning a safe situation into a dangerous one. All I can do is give pertinent traffic information, turn away other traffic if required, and, as the previous posts have pointed out, wait for the pilot to return to his cleared level. In the meantime the pilot has diverted from an ATC clearance, and is therefore legally no longer under radar control. A very nasty place to be in busy airspace.

I believe that a question such as the one posed in this topic should never need to be asked, there needs to be a global standard for this matter. I am only sorry that it took a tragedy such as we saw a couple of weeks ago to bring this discussion to the fore.