Avoiding Action: what do ATC assume?
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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!
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!
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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 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.
Here's a bit from CAP413 about the Radar Advisory Service.
The avoiding action instructions which a controller may pass to resolve a confliction with non-participating traffic will, where possible, be aimed at achieving separation which is not less than 5nm or 3000ft, except when specified otherwise by the CAA. However, it is recognised that in the event of the sudden appearance of unknown traffic, and when unknown aircraft make unpredictable changes in flight path, it is not always possible to achieve these minima.
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.
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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.
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.
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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)
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)
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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.
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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
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
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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!
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!
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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.
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.
Someone from Tech log will hopefully calculate the exact amount of bank required to make a rate one at 450 kts.
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?
Avoiding action should be given to avoid confliction or to maintain minimum separation, be it 5 or 3 miles or 1000 or 3000 feet
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 we say avoiding action this is an urgent instruction because of the immediate prospect of a serious loss of separation / collision
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.
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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!
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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!!
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!!
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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 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.
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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.
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.
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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!!
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!!
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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!
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
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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!
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!
Last edited by Crash and Burn; 18th Jun 2002 at 18:15.
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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!
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!