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

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......

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
:)

I concur with 120.4. Standard separation in Class G airspace is a luxury.

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!

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!

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...

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.

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

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)

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.

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!

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!!)

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. :eek: 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

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?

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?

"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??

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!

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.

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 ----

Jane .... I'm coming into this late in the piece, but if you think how you'd respond to a TCAS RA then I reckon you ought to give the same urgency to to an instruction from a controller such as you described - the situation probably isn't that different.
I've had drivers airframe quibble about headings issued to avoid traffic on the basis they'd fly into cloud - I usually offer them some non standard phraseology giving them the choice of flying thru either water vapour or aluminium and they then see it my way.
I also think that although standard phrases are fine 99% of the time a controller can encourage pilots to give it their all with the use of the occasional colloquialism!
:)

Bombay. Posting this on the pilots forum would be a good idea :).. I thought so to. Plane*jane didn't like it and told me so in a forthright fashion :( The thread was swiftly moved to an obscure site. Shame because the point needs serious airing amongst the pilots.

I agree strongly with Findo. I think that in the UK the situation outside controlled airspace plays a part in modifying the behaviour of pilots:

Here's a bit from CAP413 about the Radar Advisory Service.

(my italics)

Loss of 5 nm/3000 ft separation does not justify (IMHO) throwing large aeroplanes around the sky, particularly where conflictions are with slow-moving targets. Under a Radar Advisory Service, many pilots are used to being vectored around primary targets where the chance of the conflicting traffic being anywhere near their level is extremely remote.

Even though CAP413 calls the less urgent version "advice on action necessary to resolve the confliction", I cannot be the only pilot flying who, embarrassingly perhaps, has become inured to the expression "avoiding action" and was somewhat surprised to glean the consensus of this thread.

There is clearly a civil/military difference here.

As a miltary pilot I have heard the term frequently, from militrary controllers. My reaction has always been that which was taught to me some years ago in the Vale of York, ie a turn at normal rate, but initiated promptly, and before acknowledging the call (a guaranteed way to fail the sortie in normal circumstances). In those days the airspace in that area was somewhat busier than today, and the term was normally heard more than once a sortie when instrument-flying.

If civil controllers mean something more dramatic then it should be publicised very clearly.

Working Hard

Don't understand why Class G airspace will increaseas CAS decreases, perhaps you have more information.
I and many colleagues would welcome VFR calling ATC for a FIS while in Class E airspace as we could then identify the aircraft and then the conflict would not exist as the aircraft becomes known traffic. Unfortunately some VFR pilots think that ATC will restrict such aircraft and won't call us up on that basis or maybe are getting a service from the FIR in class E but would perhaps be better contacting the nearest airfield in order to get a better service. (No disrespect to the FIR guys at all)

Pub User. Unfortunately you have this the wrong way round. ALL ATC give headings all day long to achieve and protect separation. When we say avoiding action this is an urgent instruction because of the immediate prospect of a serious loss of separation / collision. If you expect to hear this several times in an IFR sortie ( about an hour ? ) then it has been an abused term which has become commonly misused by the ATC service you were using.

Avoiding Action
 

An avoiding action is just what it means, it's a turn that needs to be done immediately to avoid the loss of approved seperation between two aircraft. When ATC issues an immediate turn or an avoiding action the controller wants you to make the turn as quickly and SAFELY as the aircraft can.

I've used this phrase to some pilots who appear to take their time in turning, "Start an immediate turn to XXX or become a hood ornament on an Airbus" (or whatever aircraft is trying to run them down). The pilot ususally understands and makes the turn.

Mike R

Pub User,

As ex Mil aircrew, then in twilight years of mil career as an ex mil ATCO.. now a civ ATCO, avoiding action should not be a rate one turn - it is more urgent and is given to either maintain standard separation or, worst case scenario, to avoid collision.

If a pilot is instructed to turn under a normal instruction, he should do this straight away, (after the usual Clear left/right check and reply to ATC), using a rate one turn.... saying that Avoiding Action means turn straight away on a rate one turn implys that pilots are encouraged to hang about and dither when given normal vectoring instructions - not true, a vector turn is given for a reason, be it for spacing in the radar pattern or long range conflict resolution... it is an INSTRUCTION, not a suggestion!!!

Plain*Jane

Avoiding action should be given to avoid confliction or to maintain minimum separation, be it 5 or 3 miles or 1000 or 3000 feet and is therefore to be acted upon straight away with as much as the pilot can give us.

Avoiding Action is not ideal - conflicts should be resolved well ahead, but this is not always possible (pop up traffic, poor radar performance and even (may I say it) controller workload to name a few excuses).

MATS part 1 (JSP318A for Pub User) states that the minima are just that and can be reduced on a few occaisions - Loss of searation being one of them - however if a loss of separation situation is about to happen, then avoiding action should be used. It should be given in ample time to ensure that the action will be effective i.e. controllers should not sit and watch a situation unfold before giving avoiding turns at five miles!!

Other users may have heard mil controllers giving avoiding action to A/C about to enter CAS without authorisation... it may be pop up traffic that is fast moving, and a HARD turn is what is required to remain clear - again a justifiable and sensible use of avoiding action.

The phrase "C/S avoiding action C/S turn HARD right/left immediately....... "is not standard phraseology.. the HARD part is non standard, as pilots should be giving avoiding action the best rate of turn available at all times (with due consideration to A/C performance).. however the 'hard' does creep in because some ATCO's feel it neccesary to amplify the urgency.

Unfortunately, and civil pilots may correct me here, maybe what ATCO's expect and what pilots believe to be expected of them differ, in a large part, due to company policy??

If I, however, was a pilot of a fully laden passenger jet and was given avoiding action, I would go all out to give the hardest turn and worry about the passengers afterwards - at the end of the day, it would also be my own life I was possibly saving!

I think that some of the ATCO`s who`ve replied have no clue what kind of action it takes to yank a large aeroplane travelling at a speed of , say 450 kts TAS around a 90 degree corner at more than rate one.
No offense, Hugmonster, but even if there is such a thing as a large turboprop ;) , it is a lot simpler to do your thing in that then in a large transport jet.
If you are travelling at 450 kts TAS ( which is kinda slow in cruise), it would take about 45 degrees of bank, only to make a rate one turn! If an ATCO expects more than rate one, he would thus expect me to yank my boeing around at more than 45 degrees bank! That`s 2G`s at 450 kts. Get real!
Someone from Tech log will hopefully calculate the exact amount of bank required to make a rate one at 450 kts.

50 degrees.

I agree with seat 0A.

Am I the only person who is concerned by the lack of relative risk management displayed by some of the contributors here?

(my italics in each case)

A loss of separation is a loss of separation, not a collision. The very fact that loss of separation occurs from time to time but collisions do not should persuade you that they are not the same thing.

A loss of separation may be a deal for you, but the injuries sustained by the passengers inside an aircraft that is flung around just to avoid the snitch is a deal for them, too.

And the very idea that anyone would use the same phrase 'avoiding action' to an aircraft in no immediate danger but about to enter controlled airspace is simply absurd.

I agree with the above; if I use the phrase "avoiding action", it means "for christ's sake turn, you're about to hit someone". Frankly, it's up to you to decide what your airframe/punters can take - all I'm really doing is giving you a warning and advice. How you act on it is your call!

OA and Bookworm

I am quoting official documents - if you read my thread carefully you will see that I say that ATCOs want as much as you can give us - we do not and cannot, take into acount factors affecting rate of turn for individual A/C on specific days which include, speed, weight, control restrictions, humidity, altitude etc etc.

And yes, loss of separation IS a big thing - the minima are there to provide a buffer - it should be maintained at all times if possible - if controllers only had to control one aircraft, then this buffer could no doubt be reduced - but controlling aircraft in 10s, 20s or more over a vast airspace (2000 square miles is often norm including the height band) means that the buffer is essential.

if we were blase about the minima and thought as long as they don't collide I'm okay, then there would be collisions! That i am afraid is a fact and is why we have MINIMA!!

Seat 0A and bookworm, if you want to quibble about the sort of action you want to take, then fine. If you want to quibble about what is a large turboprop (or what is a large car, or what is a large bumblebee) then you're not addressing the issue.

What is the issue? You are being given an instruction by ATC which will heave your aricraft out of the way of something you are about to HIT. Don't think about it. Do it or you're dead.

Done that? Good. NOW you can worry about how upset the passengers are.

By the way, 0A, I do know how large "transport jets" behave. You want a list of my type ratings? Email me.

What totally confuses the issue is the military interpretation of the justifiable use of avoiding action outside controlled airspace. Civil ATC will attempt to provide at least the minimum separation under RAS but because it is generally against traffic whose intentions are unknown then that is not always achieved. That is why the minimum separation is so high. 5nm / 3,000 ft allows the pilot to participate in the avoidance of a collision. The only time the majority of civil ATCOs will use the phrase avoiding action in RAS is when there is a clear indication that there is a serious risk of very little or no separation. It is after all a radar ADVISORY service.

Inside controlled airspace the situation is entirely different. It is a known traffic environment ( apart from useless class E airspace ) and the service is radar CONTROL. Within that airspace we achieve separation not attempt separation. The pilots do not have an option to decline the instructions without very good safety reasons. ATC are working almost all the time on minimum separation which is perfectly safe and helps pack the airspace as as much as we need to keep the traffic flowing. As a result when it goes wrong and ATC need to turn an aircraft for avoiding action it is possible that MINIMUM separation has already been eroded and we want you to turn urgently.

To back up this theory I put forward one requirement from the CAA. If a civil ATCO uses the words avoiding action they are required to file a CA1261 ( Mandatory Occurrence Report ) If the situation has been caused by that ATCO, even if minimum separation was achieved by the action, then they are likely to have their licence suspended and be required to retrain. Not the sort of thing that SRG are likely to be interested in if you have used the phrase to avoid a boundary of controlled airspace which contains no aeroplanes.

The phrase is overused in the military and thankfully infrequently used in civil ATC.

So there we have it.

There is no answer and the phrase "avoiding action" means all things to all men.

There is no definitive rule on the issuing or response to the "avoiding action" call. It depends whether you are in controlled airspace receiving a radar control service or elsewhere receiving a Radar Advisory service. It depends on the controllers intonation as to whetther there is urgency and whether the controller is using the phrase to maintain separation or to avoid collision. MATS part 1 is of little help and the controller and the pilot each have only part of the story.

What a way to run a ship!!

Can I be on your plane please when you do that - wow - what fun!!!

I'd seriously love to see how that would look (and feel) - aerobatics in a Boeing eh??? The fact that the rest of the pax might be terrorised isn't a worry - I LOVE turbulence!!

TR :D;)

Assume? We never do that;)

As much as you can, as fast as you can. No messing.

ATC guys, don't forget to tell us where the heap of metal is attacking us from. Remember, if it's a constant angle it doesn't move much in the window, and the imagine only size gets bigger in the latter stages. In addition to this think about the time of day with regard to the sun.

Quick maths for you guys so you can understand the performance type stuff issues...

angle of bank (for a rate one turn) = (TAS/10) + 7

Loading 'G' = 1/Cos (Angle of Bank)

Accelerated Stall speed = Vs (unaccelerated) / (Square root of (Cos Angle of bank))

Click on the link below for a diagram

http://142.26.194.131/aerodynamics1/Lift/Page11.html

I hope this of some use, if not I'll crawl back into my hole where I came.... and I hope we never have to use the term in anger!

Thanks for the service guys, you don't get paid enough!

Hey, alforit, just accept it. The world's not perfect. This thread is fascinating - and, I am sure, something that will stick in the minds of many controllers and pilots alike. Who knows, it may even prevent a disconcerting meeting of two aircraft one day.

Speaking as a controller, I wish my world was as clear cut, with no variables, no personal foibles and no disregard of SOPs, as yours obviously is!