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Avoiding Action: what do ATC assume?

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Avoiding Action: what do ATC assume?

Old 5th Jun 2002, 21:02
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Avoiding Action: what do ATC assume?

This is a real mindblower here. When ATC gives " <callsign> avoiding action turn left heading xxx "(usually 90 degrees or more) just what is the controller expecting from the pilot? As ex blip driver at LATCC I was in no doubt in my own mind that an expedited turn was the standard manoeuvre. However I am now on line with a regional and I have to say the responses from captains etc are in the least mixed. I've had "Oh that's only for light aircraft" to one Captain in UK TMA when we went pretty close in IMC to a 733, by him tootling round with his 27 degree rate one turn for 80 degree heading change. When I most firmly demanded he get a move on (that's putting in politely), he responded that it would disturb the passengers, and steep turn shouldn't be done because of airframe considerations. Back on the ground I managed to sort THAT one out diplomatically, only to be set back on my heels by a TRI. On being told to take avoiding action on one of our training trips he was most disturbed when I pointed out that more than a rate one turn was required.
I suppose that I could ask some old chums in WD but I know that this forum in particular has some sensible civilised and most experienced members, and would genuinely appreciate the views. most firmly
PS as we crisscross UK this call is not infrequent with all the military exercises sometimes
PPS Most pilots don't realise ATC work in TAS either
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Old 5th Jun 2002, 21:20
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Plane*jane Avoiding action is exactly that, given in my case in Class g airspace it means I need as much turn rate as you and your aircraft can safely give me otherwise standard separation will not be achieved. If I use the words 'avoiding action turn hard ....' then you should give me everything you and the aircraft has or things may be considerably worse than just uncomfortable in the cabin......
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Old 5th Jun 2002, 22:27
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Stopbar:

"Avoiding action is exactly that, given in my case in Class g airspace it means I need as much turn rate as you and your aircraft can safely give me otherwise standard separation will not be achieved."

I venture to suggest that you don't actually mean that. Avoiding action gives no guarantees about standard separation, it is simply designed to try and avoid aircraft hitting each other. If you achieve standard separation, great.

It follows that with shocked passengers being better than dead ones, I expect the captain to immediately give me everything he safely can, i.e. without endangering the aircraft or occupants.

Point 4
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Old 6th Jun 2002, 00:16
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I concur with 120.4. Standard separation in Class G airspace is a luxury.
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Old 6th Jun 2002, 02:53
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Working as I do with/against class e airspace (IFR follow instructions yet VFR can do as they please WITHOUT reference to ATC) then if I give avoiding action I would expect the aircraft to commence a hard turn immediately and then complain, afterwards, as necessary!
Avoiding action is really only given if standard sep is compromised or lost.
Hope this helps!
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Old 6th Jun 2002, 06:36
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ATC has sometimes been criticized in the past, for insufficient emphasis when passing avoiding action. Hopefully the need for urgency in such situations is appreciated by both pilots and ATCOs. No system is infallible, and that includes TCAS!

Last edited by spekesoftly; 6th Jun 2002 at 06:42.
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Old 6th Jun 2002, 15:33
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Avoiding Action is just that: Action to avoid a collision with another aircraft!! Spilling the G&T should be the least of your considerations!

There was AAIB criticism recently of pilots in CAS responding to avoiding action turns by twiddling the Heading knob and turning at Rate One as already highlighted. They pointed out that the expectation was that pilots would maximum rate turn/climb/descent in accordance with the instructions. We assume that this is the case, for example if we call for an avoiding action descent that you will disconnect the A/P and push on the control column ASAP, not select a new FL and LVL CHG and wait for the nose to lower gently!

An 'avoiding action' turn in class G to achieve 5 miles/3000ft under RAS might be a different story...
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Old 6th Jun 2002, 17:07
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Don't know about the rest of you, but in the situation described by eyeinthesky above (i.e. under RAS) I wouldn't use the phrase "avoiding action" unless it was exactly that: a manoeuvre to avoid collision.

Vectoring to achieve 5Nm/3000ft I would say something like "there is traffic on your current track, vectoring you around it". Non-standard, I know, but most crews seem happy with it.
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Old 6th Jun 2002, 23:11
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GO to the CAA website and look for CAP 717 - Radar Control, Collision Avoidance Concepts

Very good small document worth a read.

Or click here:

CAP 717
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Old 7th Jun 2002, 00:10
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Bright-Ling
CAP 717 is very useful and I was hoping for definitive, when Para 3.9 wandered off in a woolly fashion describing the airframe and configuration limitations that may explain a slow response. It doesn't seem to clarify the expectation of an expedited manoeuvre, unless I've missed something. However very interesting from the controllers point of view. My point remains in that there are pilots out there UK licensed (let's not even wander off on to those pilots who do not have English as their mother tongue) who have a mixed interpretation of the actual maneouvres required in response to "avoiding action" In other words they do not see an urgency. Personally I am far from happy with this.
I also need to explain that we do not have ACAS, along with quite a few other types, and are flying in TMAs (Class A and D) where I have had this instruction at least 3 times so far this year. ATC tone in my view was urgent, direct, very specific, and the same "avoiding" instructions to the other aircraft on 2 occasions. No mistaking the urgency as far as I was concerned. Only one captain responded as I expected (ex military)
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Old 7th Jun 2002, 09:03
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Jane...I appreciate your point and agree. But para 3.9, as wooly as it is, is apt. There are many things that we should consider, but you have loads more to consider (pax strapped in, crew in aisles, aircraft weight and loading, perfomance etc etc)

All I can say is that I endorse what has been said above.

I would expect a great deal more than a gentle rate 1 turn - esp in the LTMA, where we use the 3mile horizontal minimum seperation daily.

Interesting that you say that previous AA was given in an urgent, direct and specific manner; Not sure if they were following the MATS pt 1 which says "Clear enunciation and urgent tone must be used" or whether it was panic and adrenalin!! From my experience it is always the latter.

At least the phraseology has been improved this year, so at least it should negate the "Say Again/Was that for me..." scenarios.
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Old 7th Jun 2002, 15:46
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Bright-ling.. but don't you think the new phraseology is a little verbose? If one speak clearly and emphatically the original phrase should work.. by the time one has said the thing twice the a/c might have hit!
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Old 7th Jun 2002, 17:58
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HD - I agree......but the last time I saw Avoiding Action used was replied with "was that for us!"

(And yes, they nearly did hit!!)
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Old 8th Jun 2002, 21:37
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Avoiding action … where do we start ?

As previous posts have illustrated there is a difference between RAS and radar control services. This is particularly noticeable in class G airspace where a service can be given by either a civil or military unit.

Despite the fact that civil controllers were instructed last year to “try” to achieve standard separation against unknown traffic there is a pragmatic application which only generally uses the term avoiding action if there is a serious risk of very little or no separation. On the other hand I have heard military controllers turning aircraft to avoid controlled airspace by the use of avoiding action.

I believe this is a fundamentally different approach and probably comes about because the majority of military ATCOs give RAS to aircraft that do not have to bother about upsetting the self loading freight.

Inside controlled airspace the situation is quite straightforward. If an ATCO gives avoiding action this is to avoid a collision or a serious loss of separation. ATCOs have been regularly reminded about using the phrase avoiding action and history shows when the words are used it means serious action. When a civil action actually uses the term it is mandatory they file a report and often end up suspended so this is not done lightly.

The UK Airprox Board has regularly commented about the slow reaction of some pilots in these circumstances. There is no doubt that when the term is used the pilot is expected to disengage the autopilot and turn the aircraft promptly to the assigned heading or climb / descend as instructed. Plane*jane if you want to keep this going with the company, and I suggest you do, then see Airprox 94/01 where part of the cause of the Airprox was “ and slow reaction, for whatever reason, of the B767 crew.”

I would also suggest that your company safety officer contacts the Airprox board chairman ( Gordon McRobbie) who will confirm exactly what sort of actions are considered a reasonable response to the term avoiding action. Details at UKAB
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Old 8th Jun 2002, 23:00
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If the GPWS starts blaring at me, I'm expected to take action now, without thinking about it. Anyone who doesn't can expect to end up dead.

If the TCAS goes off, I'm expected to take action now, without thinking about it. Anyone who doesn't can expect to end up dead.

If ATC tell me " ABC123 Avoiding action, turn hard right NOW", I take action now, without thinking about it. Anyone who doesn't can expect to end up dead.

I've done this. A large turboprop, slung about 60 degrees of bank on and taken it 90 degrees to my previous heading.

Apologise to the pax and give them the explanation later. I am not going to argue the toss with the controller. I do not intend to take part in a large-scale reproduction of Brownian Motion.

Anyone on a Sim check who doesn't sort out a GWPS incident correctly can expect to fail the ride. Perhaps something like this should be done for avoiding action incidents?
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Old 9th Jun 2002, 06:18
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Prof Yaffle - IF some more ATC types were to emulate the best services offered to VFR traffic (when work load permits) then perhaps many of the possible confilcts may disappear. The units giving the least possible services in Class G are well known and do a great disservice to ATC in the U.K. (civil and military alike). Not really for this thread but have you any suggestions on how this may be improved given that the extent of Class G is likely to grow with a reduction in CAS?
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Old 9th Jun 2002, 09:16
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"Not really for this thread but have you any suggestions on how this may be improved given that the extent of Class G is likely to grow with a reduction in CAS?"

Eh??
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Old 9th Jun 2002, 19:18
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Avoiding Action !

Food for thought :

Maybe this thread should be put to one of the pilots forums too !!

Quite frankly, Aircrew who treat the term "Avoiding Action" with anything less than 100% rapid reaction should wake up and smell the cheese!!

I say the term because I really mean it! so aircrew please ask questions later, I will quite happily carry the can if I over reacted, but I wont be responsible if you thought you knew best or you responded with a lack lustre approach causing a big metal shower over the UK.

Only used the term about 5 times in anger over 16 years in ATC........ Again, food for thought!
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Old 9th Jun 2002, 22:21
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Avoiding action means just that. It is not the time to piddle about. Only had it once myself as a pilot. Was in a Cessna just east of LA with "SOCAL". Called pop up twin turbo prop, 12 o'clock and told me to descend. Actions were:
1. Control column full forward.
2. Look out.
3. Drop pen and nav log simultanouesly
4. Recover to level flight.
5. Regain control of bowels and pulse.

Last edited by timzsta; 9th Jun 2002 at 22:26.
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Old 9th Jun 2002, 23:15
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I think that HugMonster has put it in the simpliest terms, just do it and answer questions later. Avoiding Action has to be the most dreaded phrase ATC can deliver, so if we use it, its damn serious.

This relates loosely to 'expedite', where we love to see max performance, and those who don't deliver - 'avoiding action' will soon follow.

---- edited for taste reasons ----
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