V1 question.
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just to further muddy the waters ...
In high surface winds with windshear likely on departure, we are allowed to add up to 15 kts to the Vr. Now lets assume that the runway is not limiting, as is often the case on my type, we have a weight book V1/Vr now with a spead of 15kts. Arguably with no FLL the V1 could sit happily under the new Vr, and the takeoff abandoned without compromising safety at that new V1. Problem is that at MTOW, there is no way to reverse calculate an "assumed weight" for the new V1 to check the FLL... probably to stop people scheduling an overweight takeoff with all the liability issues that would go with that.
This is a scenario I can envisage where I see an obvious conflict.
V1 .... long pause ... loud bang at V1+10kts with 2500m of runway ahead, thats almost twice our LDR, the temptation may well be to stop provided no rotation has been initiated.
This is a scenario I can envisage where I see an obvious conflict.
V1 .... long pause ... loud bang at V1+10kts with 2500m of runway ahead, thats almost twice our LDR, the temptation may well be to stop provided no rotation has been initiated.
Last edited by Teddy Robinson; 19th Aug 2011 at 13:05. Reason: typo.
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Defining V1
And so the very definition of V1 continues to be debated in the aviation world.
The devil is in the details as one group points out that V1 should really be called "continue/reject action speed". It is the speed at which the first positive action must be taken, not the speed at which you actually make the decision to reject.
A cursory study of available data will show that rejecting above V1 is like trying to win in Las Vegas. The odds are with the house.....
I have only rejected one takeoff and it was at rotation speed in a C23 in Iraq with about 7000 feet of runway in front of me. The flaps were not set properly and the decision was obvious. No harm, no foul. However, as a 744 FO, I don't envy any of my Captain's responsibility to reject a max gross weight whale.....
The devil is in the details as one group points out that V1 should really be called "continue/reject action speed". It is the speed at which the first positive action must be taken, not the speed at which you actually make the decision to reject.
A cursory study of available data will show that rejecting above V1 is like trying to win in Las Vegas. The odds are with the house.....
I have only rejected one takeoff and it was at rotation speed in a C23 in Iraq with about 7000 feet of runway in front of me. The flaps were not set properly and the decision was obvious. No harm, no foul. However, as a 744 FO, I don't envy any of my Captain's responsibility to reject a max gross weight whale.....
At the V1 call they remove the hands from the levers.
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It is experience. If one does not remove the hand from the thrust levers at V1 (or before) chances are very very high that take offs will be routinely aborted above V1.
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In the L'Airboos I take my hand off the throttles at V1 and
stick it on the RH armrest of me seat - till its needed to be
back on them again.
A lot of the kids have this damn annoying habit of putting
their mitts all over 'em just after rotation.
stick it on the RH armrest of me seat - till its needed to be
back on them again.
A lot of the kids have this damn annoying habit of putting
their mitts all over 'em just after rotation.
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JT
I was expecting the performance heavyweights to post in this thread.
When V1 = VR, in what cases it can be ASD limited ?
We can say that in this case, V1 is "maximum", which can be regarded as maximum ASD, minimum TOD V1. If ASDA is not infinite, at least it is enough,.
I always thought that choosing "maximum V1" is done so that we have more chances to stop and stay on the ground rather than taking off.
In the 320 I feel like doing something worthless when I calculate V1 in a 3500 m runway from which 747s and 380s are taking off. All I want to know is VR and V2. Such one day in a wet 4000 m runway we used FCOM 2 tables to substract knots to dry V1, VR and V2. I called out V1, we waited till 10 knots later and called "rotate". I think we had still 2000 m remaining...In some cases V1 is simply ridiculous. In others it has a meaning.
I look at V1 as a decision speed, in the sense that I don't intend to assess the situation too much if something happens during take off. Before V1, stop, at or above V1, go. No thinking. The thinking is made before the event. Obviously I will stop in case of a catastrophic failure. I don't know what happened to that 74 nor how a captain knows that a wing is no fire. An engine fire is no reason for rejecting after rotation, unless you are certain that there is runway enough, and that must be difficult with a 747...
I was expecting the performance heavyweights to post in this thread.
When V1 = VR, in what cases it can be ASD limited ?
We can say that in this case, V1 is "maximum", which can be regarded as maximum ASD, minimum TOD V1. If ASDA is not infinite, at least it is enough,.
I always thought that choosing "maximum V1" is done so that we have more chances to stop and stay on the ground rather than taking off.
In the 320 I feel like doing something worthless when I calculate V1 in a 3500 m runway from which 747s and 380s are taking off. All I want to know is VR and V2. Such one day in a wet 4000 m runway we used FCOM 2 tables to substract knots to dry V1, VR and V2. I called out V1, we waited till 10 knots later and called "rotate". I think we had still 2000 m remaining...In some cases V1 is simply ridiculous. In others it has a meaning.
I look at V1 as a decision speed, in the sense that I don't intend to assess the situation too much if something happens during take off. Before V1, stop, at or above V1, go. No thinking. The thinking is made before the event. Obviously I will stop in case of a catastrophic failure. I don't know what happened to that 74 nor how a captain knows that a wing is no fire. An engine fire is no reason for rejecting after rotation, unless you are certain that there is runway enough, and that must be difficult with a 747...
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What do you say we speed this thread to it's logical end?
Airlines push balanced field numbers into the over runs and weeds with reduced thrust calculations, under the guise that pushing trend monitored engines out to 30,000 hours, saving a few overhauls is worth the risk of flying it to the end, then pulling up.... Combine this with the common hiring practices of picking from the bottom of the resume pile...the most inexperienced pilots they can hire, specifically culled to take orders...a flying marsh-mellow is trained to read a checklist rather then make a decision...he is told to yank the yoke at V1, fly the wreck into the air...because statistically, if your typical pilot flies 'the numbers'..statistically he should be safe..
- unless he gets ice..
- unless he hits a few birds
- unless his seat rolls back to the rear
- unless lightning knocks out his tubes
- unless he has a flight control failure
- unless he has terrorists on board..
etc etc etc....
This philosophy is based on the idea that all scenarios have been addressed in the sim, and put into checklists...which is wrong. It's also under the guise that statistically given a choice under pressure, pilots will screw it up, make a bad decision...this of course is based on some epic mistakes made by airline captains, and certainly doesn't take into account all the non- accidents, famously averted, that never made the news, by pilots who 'thought' their way out of a jam....and many times famously disregarded the checklists that have been written by the lawyers, trying to fight a future court battle, not avert the current impending accident.
So in an effort to control the safety of airline operations, pilots are told to refer to sops and checklists...and secretly hope that nothing will happen out there, outside of the book...which happens all the time....
A pilot sitting there at the end of a 10,000 foot field, purposely moving v1 farther down the field with reduced thrust calculations, knows full well he is increasing the risk of that departure, so do his boss's, so does the FAA. Trying to justify yanking back on the yoke at V1 is really easy when all you ever see in your career at V1 is the end of the runway will building in front of you.
The rest of us have spent a lifetime flying planes where there is a mile of pavement in front of us, and just can't imagine why you'd take the wreck up in the air when you have the opportunity to safely keep the aircraft on the ground.
Airlines push balanced field numbers into the over runs and weeds with reduced thrust calculations, under the guise that pushing trend monitored engines out to 30,000 hours, saving a few overhauls is worth the risk of flying it to the end, then pulling up.... Combine this with the common hiring practices of picking from the bottom of the resume pile...the most inexperienced pilots they can hire, specifically culled to take orders...a flying marsh-mellow is trained to read a checklist rather then make a decision...he is told to yank the yoke at V1, fly the wreck into the air...because statistically, if your typical pilot flies 'the numbers'..statistically he should be safe..
- unless he gets ice..
- unless he hits a few birds
- unless his seat rolls back to the rear
- unless lightning knocks out his tubes
- unless he has a flight control failure
- unless he has terrorists on board..
etc etc etc....
This philosophy is based on the idea that all scenarios have been addressed in the sim, and put into checklists...which is wrong. It's also under the guise that statistically given a choice under pressure, pilots will screw it up, make a bad decision...this of course is based on some epic mistakes made by airline captains, and certainly doesn't take into account all the non- accidents, famously averted, that never made the news, by pilots who 'thought' their way out of a jam....and many times famously disregarded the checklists that have been written by the lawyers, trying to fight a future court battle, not avert the current impending accident.
So in an effort to control the safety of airline operations, pilots are told to refer to sops and checklists...and secretly hope that nothing will happen out there, outside of the book...which happens all the time....
A pilot sitting there at the end of a 10,000 foot field, purposely moving v1 farther down the field with reduced thrust calculations, knows full well he is increasing the risk of that departure, so do his boss's, so does the FAA. Trying to justify yanking back on the yoke at V1 is really easy when all you ever see in your career at V1 is the end of the runway will building in front of you.
The rest of us have spent a lifetime flying planes where there is a mile of pavement in front of us, and just can't imagine why you'd take the wreck up in the air when you have the opportunity to safely keep the aircraft on the ground.
Brian,
Au contraire, mon ami, I know all too well the newest version of the resident fanatic (def, someone who won't change their mind and can't change the subject). He was recently over at the Concorde thread explaining to some of the designers and operators of that elegant lady, how much in error they are.
WRH
Or is it, when reality bites? This is well plowed ground, I think.
GF
Au contraire, mon ami, I know all too well the newest version of the resident fanatic (def, someone who won't change their mind and can't change the subject). He was recently over at the Concorde thread explaining to some of the designers and operators of that elegant lady, how much in error they are.
WRH
Or is it, when reality bites? This is well plowed ground, I think.
GF
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Even if the decision was a reasonable one for those circumstances - the AAIB feels it was, and people here have suggested that the specifics of the aircraft/engine concerned go some way to backing that up - the crew were nevertheless wagering what they felt was probable disaster in-air against possible disaster on-ground. Had the outcome of the overrun been even a little worse then I suspect there would have been a lot more official questioning of the captain's decision-making.
Except in the most favourable conditions, conducting a safe rejection from above V1 (or Vr, in this case) will never be an option with any guarantee of a safe outcome; accurately weighing two unknown but high risks in an instant is going to be a challenge for any skill level.
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Why dont we just concede that SSG, whenrealityhurts, etc etc etc etc... is right, maybe his flight testing in Microsoft FSX and maybe he is a real pro and uses X-Planes, is correct, and the last 30 years of industry research, analysis and operational reviews are incorrect.
We should bow to his superior knowledge............ Henceforth, I hereby swear that I will not conduct another Flex Thrust Balanced Field Takeoff anytime in the next 24 hours.
Now I want to listen to more of his tales of daring do, I loved the one about him flying in the right seat of a Gulfstream and saving the aircraft, not to mention his tales of single pilot operations in the CJ...... Please oh aviation demigod, tell us more.
Mutt
We should bow to his superior knowledge............ Henceforth, I hereby swear that I will not conduct another Flex Thrust Balanced Field Takeoff anytime in the next 24 hours.
Now I want to listen to more of his tales of daring do, I loved the one about him flying in the right seat of a Gulfstream and saving the aircraft, not to mention his tales of single pilot operations in the CJ...... Please oh aviation demigod, tell us more.
Mutt
and it is funny how the same character does his jack-in-a-box inpersonation several times a year...
Mutt, Denti, Brian and MfS,
Let's grant that he is an active pilot, who does fly "single pilot" Citations (possibly because of a dearth of willing co-pilots) and is just not up to large airplane operations and is unwilling to learn.
GF
Let's grant that he is an active pilot, who does fly "single pilot" Citations (possibly because of a dearth of willing co-pilots) and is just not up to large airplane operations and is unwilling to learn.
GF
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Let's grant that he is an active pilot
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It is experience. If one does not remove the hand from the thrust levers at V1 (or before) chances are very very high that take offs will be routinely aborted above V1.
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Here's another aborted-past-V1 event that occurred in 1996.
Worth taking a look at...
GA865 Report PK-GIE.pdf
I'm not endorsed DC10, but harking back to my 747 days it
would appear to me that 151kt might've been the "highest
V1" in the dry case and so should have been fully respected.
Worth taking a look at...
GA865 Report PK-GIE.pdf
I'm not endorsed DC10, but harking back to my 747 days it
would appear to me that 151kt might've been the "highest
V1" in the dry case and so should have been fully respected.
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Actually sheppey, there is more than only a technical proof, there is substantial statistical data about it. Which is why boeing made it a mandatory take off procedure, at least on the 737.
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V1 for the GO case is computed for an engine failure condition.
V1 for the STOP case is thought for any kind of failure (other than braking systems...)
So if I ever have a malfunction different than an engine failure at or above V1I know that I can continue take off very well!. The airplane will lift off and climb as in a normal take off. In the STOP case, however, there is always a reasonable chance to overrun or depart the runway no matter what kind of failure you have, engine or anything else.
As a rule, GO is better than STOP, the only exceptions being failures or circumstances of a catastrophic nature that render the airplane "unflyable" (terrorist bomb explosion, total flight controls failure...).
The question is "How the heck I know the airplane is unflyable?"
V1 for the STOP case is thought for any kind of failure (other than braking systems...)
So if I ever have a malfunction different than an engine failure at or above V1I know that I can continue take off very well!. The airplane will lift off and climb as in a normal take off. In the STOP case, however, there is always a reasonable chance to overrun or depart the runway no matter what kind of failure you have, engine or anything else.
As a rule, GO is better than STOP, the only exceptions being failures or circumstances of a catastrophic nature that render the airplane "unflyable" (terrorist bomb explosion, total flight controls failure...).
The question is "How the heck I know the airplane is unflyable?"
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Microburst2002:
Short answer: You probably don't.
TWA lost a 707 at KCVG in 1967 because after V1 the F/O mistook as an engine failure the momentary noise and buffeting from passing through the engine wake of a DAL DC-9 that was stuck in the mud and trying to power his way out.
The question is "How the heck I know the airplane is unflyable?"
TWA lost a 707 at KCVG in 1967 because after V1 the F/O mistook as an engine failure the momentary noise and buffeting from passing through the engine wake of a DAL DC-9 that was stuck in the mud and trying to power his way out.
Moderator
When V1 = VR, in what cases it can be ASD limited ?
Anytime that ASD happens to be the limiting case. The point being made is that the various limitations are applied separately and whichever is limiting for the particular takeoff sets the RTOW.
If ASDA is not infinite, at least it is enough,.
Fair comment
I always thought that choosing "maximum V1" is done so that we have more chances to stop and stay on the ground rather than taking off.
Not necessarily .. and the other consideration is whether it is a good idea to make a non-limiting ASD situation limiting by pushing the V1 up as high as possible on the day.
Running to maximum V1 gets you to VR in the shortest distance which benefits the go case. Reducing to a low V1 pushes the TOD out for the benefit of a more relaxed ASD.
In some cases V1 is simply ridiculous.
If you have a lot of spare runway in front of you then, consistent with the data presented, you have the option of increasing V1 as you might see fit. Be wary of brake energy limits ...
The thinking is made before the event.
And that is the basis for risk managing SOPs.
Anytime that ASD happens to be the limiting case. The point being made is that the various limitations are applied separately and whichever is limiting for the particular takeoff sets the RTOW.
If ASDA is not infinite, at least it is enough,.
Fair comment
I always thought that choosing "maximum V1" is done so that we have more chances to stop and stay on the ground rather than taking off.
Not necessarily .. and the other consideration is whether it is a good idea to make a non-limiting ASD situation limiting by pushing the V1 up as high as possible on the day.
Running to maximum V1 gets you to VR in the shortest distance which benefits the go case. Reducing to a low V1 pushes the TOD out for the benefit of a more relaxed ASD.
In some cases V1 is simply ridiculous.
If you have a lot of spare runway in front of you then, consistent with the data presented, you have the option of increasing V1 as you might see fit. Be wary of brake energy limits ...
The thinking is made before the event.
And that is the basis for risk managing SOPs.
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aerosafety world
in this month issue there is an article about this very thread topic, related with a 737 that did RTO some 10 kt above V1, and survived. very interesting.