V1
CFMFan.
A). Tyre failure – bang, yaw. You don’t know their origin; it’s only your perception – assumptions; as is the lack of braking. At the relatively slow speed it’s safer to stop.
B). How do you know that the aircraft is unflyable – you only attempt a rotate after V1 – at those speeds there isn’t a go/no-go decision, only mitigation of the inevitable accident / speed at which you go off the end.
Never assume.
Regulatory based procedures have evolved from hard earned experience, often from the deaths of other pilots, don’t think that you know better, particularly at that critical moment in time when things may ‘appear’ not to be as expected – check the situation, follow the procedure. There is time for both - practice.
BenThere, few pilots know the distance travelled to V1 – many variables. Similarly the distance (not time) remaining to stop. What are the conditions - dry, wet, tailwind; again many variables, which even a grey-haired oldie cannot compute in a reasonable timescale.
Flying with an engine failure / fire is quite safe enough for the conditions and subsequent procedures – certainly better than attempting to stop with so many unknowns.
A). Tyre failure – bang, yaw. You don’t know their origin; it’s only your perception – assumptions; as is the lack of braking. At the relatively slow speed it’s safer to stop.
B). How do you know that the aircraft is unflyable – you only attempt a rotate after V1 – at those speeds there isn’t a go/no-go decision, only mitigation of the inevitable accident / speed at which you go off the end.
Never assume.
Regulatory based procedures have evolved from hard earned experience, often from the deaths of other pilots, don’t think that you know better, particularly at that critical moment in time when things may ‘appear’ not to be as expected – check the situation, follow the procedure. There is time for both - practice.
BenThere, few pilots know the distance travelled to V1 – many variables. Similarly the distance (not time) remaining to stop. What are the conditions - dry, wet, tailwind; again many variables, which even a grey-haired oldie cannot compute in a reasonable timescale.
Flying with an engine failure / fire is quite safe enough for the conditions and subsequent procedures – certainly better than attempting to stop with so many unknowns.
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John - Agreed.It is this black and white view that I object to....the monkey see monkey do brigade even brief predictive windshear as a V1 -1 knot stop on a nil wind/CAVOK/high pressure day!
PEI - We actually agree on the decision "at the relatively slow speed it is safer to stop" but I have not got my point across. In my company if you abandon at 90 knots for a tyre failure you will be asked why you deviated from SOPs.
What I was seeking was clarification on peoples thoughts as to WHY they favour a course of action.
You say at the relatively slow speed it is safer to stop ... if the reason is not "that you are not confident of accelerating to V1 before running out of runway"...then please advise why you would stop.
What I was saying here about the aircraft being unsafe to fly is that if you are trying to accelerate on one set of wheel rims you may well not reach VR speed.
The only other thing I can think of which would cause a ban and yaw at 90 knots would be an engine failure...which would be a stop item anyway. Again here I was just trying to get the experience of someone who has had a double tyre failure as to if these were there symptoms.
Can't agree with your never assume comment though. We get paid mega bucks to make a decision...sometimes when you are above 80 knots (and as John describes it) at a margin below V1 things other than engine fire/failure/PWS will happen. Sticking with the procedure may well result in a take off considerably less safe than the low speed abort.
PEI - We actually agree on the decision "at the relatively slow speed it is safer to stop" but I have not got my point across. In my company if you abandon at 90 knots for a tyre failure you will be asked why you deviated from SOPs.
What I was seeking was clarification on peoples thoughts as to WHY they favour a course of action.
You say at the relatively slow speed it is safer to stop ... if the reason is not "that you are not confident of accelerating to V1 before running out of runway"...then please advise why you would stop.
What I was saying here about the aircraft being unsafe to fly is that if you are trying to accelerate on one set of wheel rims you may well not reach VR speed.
The only other thing I can think of which would cause a ban and yaw at 90 knots would be an engine failure...which would be a stop item anyway. Again here I was just trying to get the experience of someone who has had a double tyre failure as to if these were there symptoms.
Can't agree with your never assume comment though. We get paid mega bucks to make a decision...sometimes when you are above 80 knots (and as John describes it) at a margin below V1 things other than engine fire/failure/PWS will happen. Sticking with the procedure may well result in a take off considerably less safe than the low speed abort.
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What a dilemma!!!!!!
It would be of interest to read Airbus' "Getting to Grips with Aircraft Performance'. In it is explained the evolution of the certification
standards for "V1". Interestingly, depending on when/how/under what FAR/JAR your aircraft was certified, the definition of V1 is different.
Things all started in March of 1978 with "Amendment 42". This FAA
certification amendment allowed the decision to be 2 seconds beyond
V1. The Airbus A-320 was the first and the last aircraft to be
certified under "Amendment 42".
Then, in March of 1992, the issue was revisited. As a result, now, we
have "Post Amendment 42". The two-second rule was re-adopted, but
was changed to the 'equivalent distance of two seconds'. There were
other certification changes, such as: the brakes can be worn to the
certification limits at the start of the takeoff roll (and you still must
be able to stop), dry/wet accelerate/stop certification definition and
requirements, etc. You can read it for yourself. This Airbus
publication is available on-line to anyone.
As per the Airbus FCOM, the criteria for rejecting or continuing the
takeoff are pretty explicit. Boeing uses 80 knots as a dividing line.
Airbus uses 100 knots. As per Airbus, below 100 knots, it is
'reasonable' to reject for just about any Master Caution. But,
above 100 knots, a rejected takeoff should be performed only for
a Master Warning or four Master Cautions (Sidestick, Engine Failure,
Reverser Fault, Reverser Unlocked), any fire warning or severe damage,
sudden loss of engine thrust, or an unambiguous indication that the aircraft cannot fly safely.
It should be noted that Airbus cautions against rejecting in this 'high speed regime' for reasons such as high EGT, wheel/tire vibration, etc.
Interestingly, Airbus is also explicit with regard to the issue of a
tire burst during takeoff. When within 20 knots of your V1, should
a tire burst occur, assuming there is no collateral damage to engines,
the takeoff should be continued. I used to brief, should this occur,
we'll continue the takeoff (sans serious engine damage), but we'll
keep the gear down after takeoff. The purpose of this is to preclude
jamming hot/burning/damaged gear up in the wheel wells. The
problems associated in retracting the gear in this instance are obvious.
Of course, as always, your company's SOP is the bible. However, any
issues/problems you see with the SOP can and should be brought to the
attention of your company's training department.
Fly safe,
PantLoad
standards for "V1". Interestingly, depending on when/how/under what FAR/JAR your aircraft was certified, the definition of V1 is different.
Things all started in March of 1978 with "Amendment 42". This FAA
certification amendment allowed the decision to be 2 seconds beyond
V1. The Airbus A-320 was the first and the last aircraft to be
certified under "Amendment 42".
Then, in March of 1992, the issue was revisited. As a result, now, we
have "Post Amendment 42". The two-second rule was re-adopted, but
was changed to the 'equivalent distance of two seconds'. There were
other certification changes, such as: the brakes can be worn to the
certification limits at the start of the takeoff roll (and you still must
be able to stop), dry/wet accelerate/stop certification definition and
requirements, etc. You can read it for yourself. This Airbus
publication is available on-line to anyone.
As per the Airbus FCOM, the criteria for rejecting or continuing the
takeoff are pretty explicit. Boeing uses 80 knots as a dividing line.
Airbus uses 100 knots. As per Airbus, below 100 knots, it is
'reasonable' to reject for just about any Master Caution. But,
above 100 knots, a rejected takeoff should be performed only for
a Master Warning or four Master Cautions (Sidestick, Engine Failure,
Reverser Fault, Reverser Unlocked), any fire warning or severe damage,
sudden loss of engine thrust, or an unambiguous indication that the aircraft cannot fly safely.
It should be noted that Airbus cautions against rejecting in this 'high speed regime' for reasons such as high EGT, wheel/tire vibration, etc.
Interestingly, Airbus is also explicit with regard to the issue of a
tire burst during takeoff. When within 20 knots of your V1, should
a tire burst occur, assuming there is no collateral damage to engines,
the takeoff should be continued. I used to brief, should this occur,
we'll continue the takeoff (sans serious engine damage), but we'll
keep the gear down after takeoff. The purpose of this is to preclude
jamming hot/burning/damaged gear up in the wheel wells. The
problems associated in retracting the gear in this instance are obvious.
Of course, as always, your company's SOP is the bible. However, any
issues/problems you see with the SOP can and should be brought to the
attention of your company's training department.
Fly safe,
PantLoad
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What use is it to consider a safe abort at the computed speed if one has not achieved the desired acceleration?
Why, with the aid of GPS and other devises that are able to compute acceleration, are we still using a decision based simply on speed?
For as long as I can remember, Falcon have been training their pilots to reley on accelartion BEFORE even looking at a V1 speed.
Is this not the same in airlines?
Why, with the aid of GPS and other devises that are able to compute acceleration, are we still using a decision based simply on speed?
For as long as I can remember, Falcon have been training their pilots to reley on accelartion BEFORE even looking at a V1 speed.
Is this not the same in airlines?
Unfortunately, I think accleration charts complicate the matter greatly and they don't tend to be available at least on the 'front line'anyways as that matter tends to be absorbed within the engineering assumptions made while deriving those speed. some operators comply with certain regulations in different but approved ways such as the AoA indicating system on the Lear 20 series; Falcon or those who provide the OpSpecs have perhaps gotten alternate approval for your operation
Great thread! I'm learning a good deal
PA
Great thread! I'm learning a good deal
PA
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Falcon
Clivewatson,
You've made an excellent point. The accel readout on the Falcon is quite useful. Unfortunately, Airbus hasn't got one like that. Maybe, somewhere in the inner workings of the MCDU, you can pull that up. I've never seen it, though.
The USAF method is pretty reliable, and I use a modified version of that.
It's unapproved, not SOP, probably illegal, but it also works well. That is,
as you pass the three-thousand foot marks, your speed should be at least
100 KIAS. Typically, it's 120 KIAS or thereabouts. But, if the 100 KIAS
callout occurs near or after the 3000 foot marks, you have a problem. I've used this in the Boeings and the Airbus. It works.
Now I am ready to have rocks thrown at me for this post....
Fly safe,
PantLoad
You've made an excellent point. The accel readout on the Falcon is quite useful. Unfortunately, Airbus hasn't got one like that. Maybe, somewhere in the inner workings of the MCDU, you can pull that up. I've never seen it, though.
The USAF method is pretty reliable, and I use a modified version of that.
It's unapproved, not SOP, probably illegal, but it also works well. That is,
as you pass the three-thousand foot marks, your speed should be at least
100 KIAS. Typically, it's 120 KIAS or thereabouts. But, if the 100 KIAS
callout occurs near or after the 3000 foot marks, you have a problem. I've used this in the Boeings and the Airbus. It works.
Now I am ready to have rocks thrown at me for this post....
Fly safe,
PantLoad
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Now I am ready to have rocks thrown at me for this post
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great thread, I agree. The topic "aborting for reactive wind shear" was brought up here somewhere earlier, I believe. In my eyes, that's probably one of the kind and can cause great deal of trouble. I'd even regard to that as something like "toss the coin" decision. If one had a bit less tail wind, in case of rejected take off, no overrun would have happened though if there was a bit less tail wind, in case of continued take off, one could have got airborne safely. Not sure if there's a reliable panacea for this nature's trick except to delay the take off. The dilemma is caused by a difference between the actual speed of a/c and the indicated one, making void all the inputs used for take off calculation. The rest is pretty much clear and any kind of assumption isn't really appropriate. My 2 cents.
Cheers
Cheers
CFMFan, within our agreement, we appear to have similar lines of thought, but perhaps from differing conceptual bases.
RE: if the reason is not "that you are not confident of accelerating to V1 before running out of runway"
These are not my words or thoughts. Judgement of such an acceleration capability would require great experience and ideal conditions in situations with a vast range of variables.
It is often within an individuals’ quest for confidence that error arise. We have confidence from every day operation that normal take-off performance provides the required level of safety; why then do some people question abnormal performance at a critical stage of operation.
IMHO the addition of phrase “if the aircraft is unable to fly” in the Take Off Training Aid (FAA doc – Boeing addition – Airbus followed for consistency) creates many problems and has decreased safety. If ‘something’ occurs before V1, the ‘decision’ requires you to predict the future – will it fly.
The text introduces a new evaluation and decision loop for a subject (will the aircraft fly with this ‘unknown/assumed’ failure) where few pilots have training or experience (knowledge).
As stated previously, the prime indications of inability to fly occur after V1, at or after rotation, when the stick is pulled back; even then it might fly later at a higher speed. All of this has nothing to do with engine failure recognition, V1, or RTO training – other than the mistaken perceptions. See: Canadian view – After V1.
The example of a tyre / wheel failure reducing performance is based on the premise that the pilots knows that the tyre / wheel has failed – and that it will reduce performance by a hazardous amount.
I suggest that both of these are most unlikely; a bang and yaw are not unique features – a galley door + wind gust, an engine failure, etc. At low speed there may be opportunity for discrimination based on salience or pilot experience, but at high speed, past accidents identified human fallibility, particularly when stressed, often by the surprise of an event. For a performance example see this Accident Report.
Many operators brief only to stop for problems other than engine failure and fire below a certain speed (80kts).
At lower speeds it appears to be assumed (operational regulations/training) that other non-engine failures can be evaluated / established and that the risks in stopping are low – and little is lost in being wrong.
At higher speeds the decision task should be simplified to identifying an engine failure – specifically lack of thrust, as that is a critical parameter for continued safe flight.
IF engine failure (lack of thrust), AND speed less than V1, THEN stop; caveat about having taken the first actions before V1 (certification regulations).
Thus training should concentrate on engine failure recognition (thrust parameter and confirming indications) and the human frailties involving startle, loud noises, vibration etc, false beliefs / perceptions, and assumptions.
Assumptions? – “there are no truths, only perceptions”. I agree that pilots in rare situations are required to make risky judgments – based on assumptions from their perceptions. However, these decisions should not be made without first verifying the basis of the assumption (the risks in assuming …).
Certification regulations balance risks to match the required level of safety, i.e. there is some margin, and thus operating procedures should guide pilots in most circumstances – engine failure +/- V1 is covered.
RTO guidance for non-engine related failures is weak, hence the FAA training aid, but when that also has weaknesses … … Perhaps this is the reason for operators using V1- 20kts or 80kts for non-engine related failures, but not to treat these situations as the same thing as an engine failure.
I agree that crews should follow the procedures, but it does not prevent them enquiring about the basis of procedures. I wonder what management might have assumed about RTOs with tyre / wheel failure; how do they expect crews to identify the fault (an assumption) – how are crew’s to differentiate this from an engine failure. Are you trained for that, is it written down?
Don’t let management pass the buck to the individual – seek clarification.
Also see:
PSM+ICR.
Briefing Notes; see ‘Revisiting the “Stop or Go” Decision’, under Takeoff and Departure Operations.
RE: if the reason is not "that you are not confident of accelerating to V1 before running out of runway"
These are not my words or thoughts. Judgement of such an acceleration capability would require great experience and ideal conditions in situations with a vast range of variables.
It is often within an individuals’ quest for confidence that error arise. We have confidence from every day operation that normal take-off performance provides the required level of safety; why then do some people question abnormal performance at a critical stage of operation.
IMHO the addition of phrase “if the aircraft is unable to fly” in the Take Off Training Aid (FAA doc – Boeing addition – Airbus followed for consistency) creates many problems and has decreased safety. If ‘something’ occurs before V1, the ‘decision’ requires you to predict the future – will it fly.
The text introduces a new evaluation and decision loop for a subject (will the aircraft fly with this ‘unknown/assumed’ failure) where few pilots have training or experience (knowledge).
As stated previously, the prime indications of inability to fly occur after V1, at or after rotation, when the stick is pulled back; even then it might fly later at a higher speed. All of this has nothing to do with engine failure recognition, V1, or RTO training – other than the mistaken perceptions. See: Canadian view – After V1.
The example of a tyre / wheel failure reducing performance is based on the premise that the pilots knows that the tyre / wheel has failed – and that it will reduce performance by a hazardous amount.
I suggest that both of these are most unlikely; a bang and yaw are not unique features – a galley door + wind gust, an engine failure, etc. At low speed there may be opportunity for discrimination based on salience or pilot experience, but at high speed, past accidents identified human fallibility, particularly when stressed, often by the surprise of an event. For a performance example see this Accident Report.
Many operators brief only to stop for problems other than engine failure and fire below a certain speed (80kts).
At lower speeds it appears to be assumed (operational regulations/training) that other non-engine failures can be evaluated / established and that the risks in stopping are low – and little is lost in being wrong.
At higher speeds the decision task should be simplified to identifying an engine failure – specifically lack of thrust, as that is a critical parameter for continued safe flight.
IF engine failure (lack of thrust), AND speed less than V1, THEN stop; caveat about having taken the first actions before V1 (certification regulations).
Thus training should concentrate on engine failure recognition (thrust parameter and confirming indications) and the human frailties involving startle, loud noises, vibration etc, false beliefs / perceptions, and assumptions.
Assumptions? – “there are no truths, only perceptions”. I agree that pilots in rare situations are required to make risky judgments – based on assumptions from their perceptions. However, these decisions should not be made without first verifying the basis of the assumption (the risks in assuming …).
Certification regulations balance risks to match the required level of safety, i.e. there is some margin, and thus operating procedures should guide pilots in most circumstances – engine failure +/- V1 is covered.
RTO guidance for non-engine related failures is weak, hence the FAA training aid, but when that also has weaknesses … … Perhaps this is the reason for operators using V1- 20kts or 80kts for non-engine related failures, but not to treat these situations as the same thing as an engine failure.
I agree that crews should follow the procedures, but it does not prevent them enquiring about the basis of procedures. I wonder what management might have assumed about RTOs with tyre / wheel failure; how do they expect crews to identify the fault (an assumption) – how are crew’s to differentiate this from an engine failure. Are you trained for that, is it written down?
Don’t let management pass the buck to the individual – seek clarification.
Also see:
PSM+ICR.
Briefing Notes; see ‘Revisiting the “Stop or Go” Decision’, under Takeoff and Departure Operations.
