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Aborted Takeoff After V1?

Sun Jul 30, 2000 11:57 am

A question for the readers (pilots/passengers) of this forum; have you been in a situation where you had to abort a takeoff after V1 call (or a takeoff was aborted)? How much time do you have after V1 to abort a takeoff before the aircraft reaches V2, specially if it is a fully loaded 747?
Thanks in advance for your response.

AJ
 
fr8tdog
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RE: Aborted Takeoff After V1?

Sun Jul 30, 2000 3:07 pm

The term V1 is "Takeoff decision speed", meaning that up to that speed an abort will allow suffucient distance to stop on the available runway remaining. The only time that you would want to abort after that speed is a structure failure or something that would cause the aircraft not to fly.
The Regional airline that I work for, trains us to continue the take off after V1 for an engine failure or even if the engine is on fire. The only fire that the Captain might abort for is, cockpit smoke or something similar.
Aborting after V1 is very risky buisiness, Most likely the outcome is going to be more risk in pax injury or aircraft damage.
Paul
 
JETPILOT
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RE: Aborted Takeoff After V1?

Sun Jul 30, 2000 4:45 pm

One important thing to remember is that V1 is figured without the use of reverse thrust. Only maximum wheel braking. So you have that going for you in an abort after V1.

The amount of time it takes to reach V2 after V1 is infinetly variable. It is different for every airplane, on every runway at any given temperature and altitude.

More importantly the two speeds are unrelated.

V1 is a ground speed, and V2 is an airspeed.
 
aaron atp
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V1

Sun Jul 30, 2000 5:10 pm

hypothetical situation: job interview question

The instant after you reach V1 the #2 goes critical; what do you do?

well, if you thought about the answer for more than one second before deciding, you shouldn't worry about moving to the next step of the interview process.


fr8dog's right, unless the wings have fallen off, instinct should take over and you shouldn't even hesitate before continuing the takeoff. That is what pilots are trained to do. The question probably stemmed from the concorde incident, and without question I will state that the captain made the right decision given the information at hand. He did what he was trained to do; after V1 you do not hesitate.



aaron
 
dash8tech
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RE: Aborted Takeoff After V1?

Sun Aug 13, 2000 4:50 pm

I was talking to one of our pilots after he had aborted at take-off speed about this very subject not too long ago. He said since the Dash-8 can stop and start on a dime especially with the long runway he had in PSC that overall it is his decision depending on situation. His was possible control problem. The yoke made an un-commanded roll as they were passing through V1, shortly thereafter he aborted. He told me that an engine fire-he goes, engine problem-he goes etc...but control problem he goes NOT! Good thing, for all he knew it could have flipped him right after rotation into the ground. (Turned out to be a switch-factory installed- in an aileron panel had finally rubbed through a composite panel because it was installed backwards).

Cheers!
 
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V1 Based On Ground Speed?

Mon Aug 14, 2000 2:45 am

If V1 is based on ground speed how do know when it is reached? I haven't flown any airplanes that indicate the ground speed on the take off roll.
 
aaron atp
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C172sb

Mon Aug 14, 2000 3:33 am

I think you are reading too much into his statement.

V1 and V2 are fundamentally different. It doesn't matter what your speed through an airmass is for V1, because the groundspeed is what determines your ability to stop on the remaining runway.

Yes, both V1 and V2 callouts are read from the airspeed indicator, but the amount of air moving over the wings is only important for V2.




aaron
 
koopas
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RE: Aborted Takeoff After V1?

Mon Aug 14, 2000 6:19 am

To induce the maximum amount of drag (and friction!), is it possible to retract the gears while rolling, after V1, in the case of a catastrophic structural failure such as the loss of a wing? With the gears retracted (the airplane skidding), full reverse thrust, wouldn't you stand a better chance of stopping before the end of the runway?
 
fr8tdog
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RE: Aborted Takeoff After V1?

Thu Aug 24, 2000 9:35 am

Well koopas thats a valid point.
but there is a multitude of other factors to consider...
the gear may not retract if there is sufficient weight on on the WOW switches (squat switches). If the gear does retract. the aircraft is basiclly uncontrollable, the risk of fire is greatly enhanced and the risk of serious injury's are increased. And quite possibly increased risk to the passengers during an evacuation procedure.
If I was faced with that descision.. No I would not retract the gear while I am on the ground.
 
aaron atp
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Koopas

Thu Aug 24, 2000 10:23 am

The coefficient of kinetic (sliding) friction between aluminum and concrete is lower than the rolling Cf between rubber and asphalt. That means you would slide further.

Once again, if the wings fell off, the engines and thrust reversers probably fell off too. If the engines didn't fall off, the shock of hitting the ground in such a violent manner when you retracted the gear probably rendered them inop anyway. Also, your chances of having all 3 gear retract successfully would be nil; 1 or 2 may retract, then the a/c would start some rather nasty gymnastics before ripping the rest of the ground tackle off.


aaron
 
MrFord
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RE: Aborted Takeoff After V1?

Tue Apr 05, 2011 9:01 pm

Also, to answer your question regarding the time between V1 and V2, you can be in a situation were V1=VR, similar to what Dash8tech brought up. In that case, the plane will want to fly before you will reach the critical point where you would run out of runway in case of a rejected take-off.

At that point, unless you specifically force the plane down the runway, or as it happened before, you take-off then settle right back on the runway, then you are already flying. It is then safer to come back around.

If you're flying a Twin Otter out of a 12,000ft runway, you can safely assume that you could take-off and land a couple time before running out of pavement; it is very rarely the case in an airliner.

Good example: http://aviation-safety.net/database/record.php?id=19920730-0


Keep in mind that V2 is a minimum maneuverability speed ; you should be in the air before you reach V2.
"For radar identification throw your jumpseat rider out the window."
 
tb727
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 12:29 am

Holy crap! I don't think I've ever seen a thread resurrected after over 10 years! lol
Too lazy to work, too scared to steal!
 
flymia
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 3:18 am

Ok I was going to get into the thread but yea its 10 years old. Never mind. But will say it all depends on the aircraft too like a Dash-8 will stop after V1 a 744 might not.

Quoting Dash8tech (Reply 4):
I was talking to one of our pilots after he had aborted at take-off speed about this very subject not too long ago. He said since the Dash-8 can stop and start on a dime especially with the long runway

This thread was made before I even joined airliners!
"It was just four of us on the flight deck, trying to do our job" (Captain Al Haynes)
 
Mastropiero
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 12:29 pm

Quoting Dash8tech (Reply 4):
The yoke made an un-commanded roll as they were passing through V1, shortly thereafter he aborted. He told me that an engine fire-he goes, engine problem-he goes etc...but control problem he goes NOT!

Ok, probably VERY silly question, but how noticeable is an un-commanded roll with all three landing gears still on the ground? I imagine by that time the plane has allready (almost?) complete aileron authority, correct?

So, would that mean that the plane would initiate a banking movement even if it was still on the ground?
 
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Starlionblue
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 2:52 pm

Quoting Koopas (Reply 7):
To induce the maximum amount of drag (and friction!), is it possible to retract the gears while rolling, after V1, in the case of a catastrophic structural failure such as the loss of a wing? With the gears retracted (the airplane skidding), full reverse thrust, wouldn't you stand a better chance of stopping before the end of the runway?

This subject is still endlessly debated among motorcyclists. There are old-school types who think that "laying her down" is more effective than braking as a last ditch stopping method. Same story there. No way metal on asphalt has more friction than rubber on asphalt.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
chuchoteur
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 3:07 pm

Quoting tb727 (Reply 11):

Holy crap! I don't think I've ever seen a thread resurrected after over 10 years! lol

Actually looks like the thread originator isn't here anymore?
LoL
 
Miercat
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 6:09 pm

In before lock?

Seriously it's been 10 years, I was 6 when this test came out.
Happiness is V1 in KEWR
 
MrFord
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 7:37 pm

Quoting tb727 (Reply 11):
Holy crap! I don't think I've ever seen a thread resurrected after over 10 years! lol

Woooaaaa my bad! So sorry, for some reasons, the thread appeared with all the recent ones. Never, ever thought of checking the date.
My mistake!
"For radar identification throw your jumpseat rider out the window."
 
PolymerPlane
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RE: Aborted Takeoff After V1?

Wed Apr 06, 2011 7:48 pm

NVM I was wrong

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[Edited 2011-04-06 13:07:09]
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ThirtyEcho
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RE: Aborted Takeoff After V1?

Thu Apr 07, 2011 2:58 am

V1 is based on ground speed? Huh?

Gotta go to the auto junkyard and buy a speedometer off of an old car. I've been doing it wrong all these years.
 
PGNCS
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RE: Aborted Takeoff After V1?

Thu Apr 07, 2011 6:56 pm

Abort above V1?

Only if I am completely convinced the airplane cannot be flown.

The topic is very thoroughly discussed in this report from the NTSB.

http://www.airdisaster.com/reports/ntsb/AAR93-04.pdf
 
cbphoto
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RE: Aborted Takeoff After V1?

Thu Apr 07, 2011 8:43 pm

Even though this thread was created before this incident, this is a classic example of what could happen with a botched abort after V1!



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BoeingGuy
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RE: Aborted Takeoff After V1?

Thu Apr 07, 2011 10:01 pm

V1 is based on airspeed, at least on Boeing airplanes.

The Boeing manuals state to only abort after V1 if, in the captain's judgement the airplane is incapable of safe flight. Everything else, you continue after V1.

In fact, Boeing's philosophy is to abort above 80 knots only for:

* Engine Fail
* Fire or fire warning
* Predicitive Windshear Warning (which is itself inhibited above 100 kts)
* The airplane is unsafe to fly

Everything else, you continue above 80 knots including: Window opening, Advisory message, Tire failure, etc.

As others have pointed out, a lot of bad things can happen when aborting takeoff at high speed. Worse can happen when aborting above V1. However, obviously if you hit birds above V1 and both engines failure, you aren't flying anywhere, for example. That's one extreme example of where an RTO above V1 would be justified (and obviously necessary in this example). A serious flight control jam or problem in which the captain believes the airplane would not be able to fly safely would be another.

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