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Kestrel Mayday (TCAS discussion)

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Kestrel Mayday (TCAS discussion)

Old 13th Mar 2003, 19:33
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TCAS does not know which type of aircraft it is attached to.
TCAS does not know how high you are flying.
TCAS does not know about the performance of the aircraft.
It may ask you to climb when you are flying at your maximum altitude. It may give you commands to climb at a higher rate than you are able to.
TCAS does not know if you are flying on QNH or STD. It uses STD.
TCAS does not know which altitude you have set for level off.

TCAS does know your altitude relative to that of other traffic, and the closure rate. It will coordinate evasive action between you and another aircraft.
Setting TA ONLY in an engine failure situation will inform the other TCAS that you will NOT be able to make any evasive maneuvers, and the other aircraft will receive commands based on this. Smart thing to do.
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Old 14th Mar 2003, 08:13
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First, may I offer Faustino's rules of thumb?

Mayday - if the successful and safe outcome of the event is in doubt.

Pan - assistance and/or priority is required but the event will be safely concluded.

So, engine failure - Pan, reverser unlock in flight - Mayday.

Another way to think about it is: Is the situation stable or unstable, and is it life-threatening or not? If non-life threatening and stable, Pan; if either unstable or life-threatening (or both!!), Mayday.

My exception to this is that in any state bordering the Med, I would never use Pan. I know that Pan calls have been ignored in at least some of these states and base my opinion on this knowledge.

I'd rather not read bald statements about this being the 'Captain's call'. The Captain may initiate the judgement, but should definitely consider the views of the other crew members in the flight deck.

Onto TCAS, I have no problem with opinions being offered here, but they should not appear as facts. TCAS is massively misunderstood by pilots and ATCOs alike. Some of what ManaAdaSystem says is correct, and some is wrong. Anyone like to guess which bits are which?

ferris, in law, an ATC instruction has precedence over a TCAS RA. (Tokyo convention). Wait and see who carries the can for Bodensee before we draw conclusions. A Commander who disobeys an ATC instruction in order to follow an RA assumes responsibility for the safety of his aircraft and absolves ATC of their element of such responsibility.
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Old 14th Mar 2003, 08:23
  #43 (permalink)  
 
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Back to the aircraft involved, I was back in BCN yesterday and it was A320 G-SSAS and the engineers were working on the right engine with a new one sitting on the ramp next to the aeroplane.

Somebody said earlier about this becoming another Airbus-Boeing thread over this, why should that be, it was the engine that gave way, not the airframe.
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Old 14th Mar 2003, 08:37
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<<First, may I offer Faustino's rules of thumb?

Mayday - if the successful and safe outcome of the event is in doubt.

Pan - assistance and/or priority is required but the event will be safely concluded. >>

I'm afraid to disagree. There are ICAO definitions of these words, and they differ from yours in some specific circumstances (one of which we are discussing here).

Back to first principles - why are we using the pro-word? It has nothing to do with the Flight Crew, their actions, or even the danger they face. It is to do with the level of assistance you, as Flt Crew, require, and the consequences of not getting it in the timescale required... All very neatly covered in the ICAO definitions...

NoD
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Old 14th Mar 2003, 10:19
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OK Ghostflyer and anyone else interested in this thread:

Do you see where I'm coming from about lack of understanding of TCAS and the rules governing it?

Faustino; did you get what I meant when I said I believe that when you (rapidly) descend without clearance, you are quite possibly in 'grave and imminent danger', thereby warranting a Mayday? And out of interest, what company do you fly for and what is their SOP for TCAS RA? After Bodensee I asked a straw-poll question on this subject (in the aircrew questions forum), and every reply was that "we follow RA over ATC" (as far as was disclosed, all these responses were from US or 'western' carriers).

I had hoped some lessons were learned after Bodensee. Obviously not.

ps In the UK, US, Australia and the UAE (these are the places I have actually checked the rules), you are expected to follow an RA over an ATC instruction (although, possibly ambiguously once again, the rules are phrased with 'should' rather than 'shall').

edited for spelin
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Old 14th Mar 2003, 11:37
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Something that doesn't appear in this discusion, but I think should, is changing squawk to 7700 - particually if your emergency is going to result in an immeadiate deviation from your cleared flightpath or level.

As an ATCO I have never seen the squawk changed on pilot initiative in an emergency, only when instructed by ATC. Does it appear nowhere in the emergency check list or is SOP to wait for ATC instruction?

In the context of this thread, squawking 7700 coincidently with making a MAYDAY call, helps ATC hugely with our response as it alerts all sectors, not just the one you're talking to.
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Old 14th Mar 2003, 12:48
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Good point Arkady.

The only place where it (7700) is written is in our emergency descent procedure.

As to "spot the errors" in my TCAS post, I would like to point out that TCAS indeed knows what FL you are flying at, but it doesn't care. It may issue a climb RA when you are flying at max certified altitude.
It also uses Radio Alt when you are operating near the ground, but may still issue a descend RA into the ground when you are flying over terrain.

Declaring an emergency is the commanderís decision. Thatís the law, at least where I am. If he is smart, he will use all available resources before making that decision.
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Old 14th Mar 2003, 13:11
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Faustino you said

........assumes responsibility for the safety of his aircraft and absolves ATC of their element of such responsibility.
I could have sworn that I have responsibility for the safety of any aircraft that I am in command of from the beginning to the end of the flight.

If I get a TCAS RA rest assured I will be following it unless I can see a very good reason not to!
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Old 14th Mar 2003, 17:49
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M.Mouse, Faustino didn't quite get the wording right. In my land, you are expected to follow an RA when issued, and then become solely responsible for separation in every class of airspace, absolving ATC of any direct command or responsibility. We are taught to pass traffic only if though pertinent, otherwise 'Roger' the call and await 'clear of conflict, returning to level...' whereby we again announce you under a Radar Control Service (if applicable). Yes you are right by saying "I have responsibility for the safety of any aircraft that I am in command of from the beginning to the end of the flight.", however part of this is OBEYING an executive ATC instruction inside CAS, and informing if unable to do so stating a plausable reason. I agree following an RA is definately the best action in todays world, but in certain places it could get very lonely when all the separation becomes your responsibility, we'll do our bit, but how much can we do????
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Old 14th Mar 2003, 18:49
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Fair dinkum, how simple could this be. Either everyone follows the RA, or it's a waste of time and a recipe for disaster.

5milesbaby, Faustino and others
UK RULES OF THE AIR
CAP717 RADAR CONTROL- COLLISION AVOIDANCE
Page 4, para 3.5
A pilot faced with conflicting instructions from a controller and an ACAS system should follow the ACAS advice.

UK AIR NAVIGATION ORDERS
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)).

UK MATS Part-1
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 maneuvers 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.


Need I go on? All this is available on the net.
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Old 14th Mar 2003, 18:53
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Arkady

Good point. However, I believe I was taught that if you are receiving an ATC service with a squawk, one should keep it in an emergency unless ATC ask you to change it. You only self select 7700 when without a service. That's the theory...

However, within my limited understanding of ATC systems, I believe the filters on your radars are such that you only see "your traffic" / area/ FL band. In case of an (uncleared) emergency descent, 7700 will show me on EVERYONE'S scope, and is thus a good idea...

More input welcome on this...

NoD
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Old 14th Mar 2003, 19:14
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Putting 7700 on the transponder is fine in theory, but - "when you are up to your ass in alligators.......". I think most of us will put 7700 on when we get round to it, but the R/T call to ATC will come a few stages before we do it unprompted.
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Old 14th Mar 2003, 19:57
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Mana - sorry mate, you are not completely correct with your TCAS info. It may well be the kit fitted to your aircraft, but ours will not issue a descent into terrain (no RAs below 1450ft and GPWS takes precedence over TCAS in any case), nor will it demand a climb above max available FL.

Max available FL is dependent on weight on heavy jets, and our system feeds the max available perf. into the TCAS kit - it will not demand an RA that cannot be complied with.

The only problem it has is with the engine-out scenario - the FMC and other systems do not feed TCAS that info and it still assumes max perf. available.
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Old 14th Mar 2003, 22:28
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Good discussion!

ferris, 'should' does not equal 'must'. You will find the word 'must' absent from TCAS operating instructions as legislation takes no account of TCAS nor places any responsibility on pilots to obey it.

5milesbaby, I should have been more specific. A better way of putting it is to say that a pilot who follows an RA and has a collision is very probably responsible, in law, for the collision. In CAS, the law requires you to obey ATC instructions (in broad terms).

M.Mouse, same point. And no, you do not have ultimate responsibility for safety. You or your company share that responsibility with, for example, their regulator, contracted providers of training and maintenance, parts suppliers, refuelling companies, airport authorities... need I go on? Your company audit most of these risk-sharers, but not ATC. I'm sure the DHL crew would have shared the sentiment in your final sentence. None of the publications you mention are Statute Instruments. None of them say 'must'.

NigelonDraft, I only offered an opinion!! It works for me and for colleagues, especially when analysing incidents etc, and no rule of thumb is bulletproof. Your point about emergency SSR codes forcing targets/tracks through filtered displays is a very valid one.

ManaAdaSystem, if you are at max certified altitude and receive a 'climb' RA there is nothing wrong with following it provided you do not bank significantly (max, say, 15deg AOB). Certification limits are not an issue and you need to understand the manoeuvre limits at certified ceiling (and at V2, V2 +15, etc).

I'm giving more thought to ferris' other points. I fly for a major European airline and our SOPs reflect the state of the legislation and advice.

Last edited by Faustino; 15th Mar 2003 at 21:38.
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Old 14th Mar 2003, 23:18
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Just for anybody who is interested in the engine type, if it was indeed G-SSAS then that a/c is an A320-231 equipped with IAE engines. Not sure if the whole MYT A320 fleet is or not.

Regards
pipersg
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Old 16th Mar 2003, 00:20
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Talking

Frpm an ATC point of view on this, when an aircraft declares and emergency be it a PAN, MAYDAY or a WE'VE GOT A PROBLEM, we have set procedures ( a checklist that we have to go through):

1. POSITION, inform the pilots of their position and advise nearest suitable airfields.

2. PERFORMANCE: How is the aircraft performance affected (i.e loss of an engine = direction of turn)

3. INTENTIONS: Ask the crew their intentions

The list goes on to subjects such as what help we as controllers can give, changing to a discreet frequency/ clearing the frequency.

However the last point is NEVER assume the crew are too busy to talk.

I've dealt with many emergencies in my time as a controller and I've only ever lost one aircraft.

We will do everything in our power to get you on the ground safely (moving heaven and earth if necessary along with all the other aircraft in the hold below you if an emergency desecent is required)

There are lots of things we need to know (for the emergency services) therefore we will need to ask questions, if you're too busy then a STANDBY will suffice, but dont forget about us, I had a crew with a u/c problem declare a mayday, asked me to standby and then promptly flew outside controlled airspace at a NON terrain safe level (after I'd asked them to climb).

Were here to help!!!!!!!!!!!!!

As an aside, since we're not allowed flight deck / js rides anymore, how about simulator visits when you guys do your checks????
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Old 16th Mar 2003, 05:56
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Faustino: TCAS not accounted for in legislation? None of the docs mentioned are 'statute instruments'?
You better stick to flying, as your lawyering sucks. Where do you think the power to create the ANOs, Rules Of The Air etc comes from?

You are quite correct in saying 'should' doesn't equal 'must' (or 'shall'), I had already pointed that out in an earlier post. The reason the imperitive is not used, is to allow the crew discretion in taking avoiding action. eg if you visually aquire the traffic and elect to turn to avoid, rather than climb or descend as per RA. If the imperitive was used, then you would be committing an offence automatically and axiomatically by not following an RA. Avoid the accident, but still get charged- not ideal.

I disagree that a pilot following an RA and has a collision is responsible at law. That is your opinion, and not a fact. IMHO, a pilot who follows an ATC instruction and has a collision will, ultimately, bear some of the responsibility (at law).

Bottom line. A lot of time has passed since Bodensee, and still the confusion about TCAS, RAs, hierarchy of responsibilties and priorities etc abounds.
A lot of US and UK pilots staunch in their conviction that they will follow the RA, no matter what. Not going to help you one bit when you smack into Faustino or his 'large European carrier' buddies.
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Old 16th Mar 2003, 11:14
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ferris

"Should" is wishy-washy

"Is most heavily recommended" is the terminology I would use here - why, you are not automatically in breach, as you would be with a "must", but it should be clear to all that way that - unless there is a most compelling reason not to, such as "can't for some overriding reason - YOU WILL.

As an observing PAX - this is one of the best threads for a long time guys.
Getting it out on electronic paper and talking it through has got to help make the right conclusions work their way through.

Cross-over training seems to me to be a most advisable way to go - and ATC's MUST be allowed jump seat as part of their, out of scope, training (sorry could not resist that one) - and off duty pilots - fix to see your friendly ATC's.
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Old 16th Mar 2003, 13:13
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I seem to remember a 146 declaring a PAN call in Spain a few years back and it caused total confusion with ATC.
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Old 16th Mar 2003, 19:45
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This is a great thread, and I would hate it to become less than that because of any aggressive words used. However, I would like to continue in the debate.

ferris and I obviously have some different ideas. But, I would ask ferris which of the documents he referred to are SIs. Yes, the power to create those documents and to impose restrictions of flying etc are ensconced within SIs, but the content of the documents mentioned does not amount to Law. My experience of prosecutions in the UK indicates to me the importance of comprehending this. I am also at a loss to know where I might find a piece of legislation about TCAS. If anyone wants to prove me wrong, please post detail!!

Regarding liability, regular briefs on the Bodensee accident from two of the investigation organisations involved come my way. May I invite ferris to wait and see where the blame is placed by the courts and who pays out before we decide what's going to be what.

The perceived allegation that I would not follow an RA is without foundation. I will do whatever is most likely to ensure the safety of my aircraft at a given time.

The fact is, TCAS is not a perfect piece of kit, and it is interesting to note that many TCAS events are not correctly dealt with by flight deck crews. Misuse of TCAS can make it a collsion guidance tool.
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