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Aborted Takeoff After V1?  
User currently offlineSbbre44 From , joined Dec 1969, posts, RR:
Posted (14 years 1 month 4 days 19 hours ago) and read 6681 times:

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

22 replies: All unread, jump to last
 
User currently offlineFr8tdog From United States of America, joined Feb 2000, 120 posts, RR: 0
Reply 1, posted (14 years 1 month 4 days 15 hours ago) and read 6470 times:

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


User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 2, posted (14 years 1 month 4 days 14 hours ago) and read 6449 times:

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.


User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 3, posted (14 years 1 month 4 days 13 hours ago) and read 6421 times:

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


User currently offlineDash8tech From United States of America, joined Jul 1999, 732 posts, RR: 5
Reply 4, posted (14 years 2 weeks 6 days 14 hours ago) and read 6299 times:

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!


User currently offlineC172sb From , joined Dec 1969, posts, RR:
Reply 5, posted (14 years 2 weeks 6 days 4 hours ago) and read 6268 times:

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.

User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 6, posted (14 years 2 weeks 6 days 3 hours ago) and read 6271 times:

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


User currently offlineKoopas From United States of America, joined Oct 1999, 172 posts, RR: 1
Reply 7, posted (14 years 2 weeks 6 days ago) and read 6264 times:

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?

User currently offlineFr8tdog From United States of America, joined Feb 2000, 120 posts, RR: 0
Reply 8, posted (14 years 1 week 2 days 21 hours ago) and read 6209 times:

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.


User currently offlineAaron atp From United States of America, joined Mar 2000, 533 posts, RR: 2
Reply 9, posted (14 years 1 week 2 days 20 hours ago) and read 6203 times:

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


User currently offlineMrFord From Canada, joined Jan 2001, 143 posts, RR: 1
Reply 10, posted (3 years 4 months 4 weeks 10 hours ago) and read 5459 times:

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."
User currently offlinetb727 From United States of America, joined Jun 2005, 1588 posts, RR: 9
Reply 11, posted (3 years 4 months 4 weeks 6 hours ago) and read 5360 times:

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!
User currently offlineflymia From United States of America, joined Jun 2001, 7147 posts, RR: 9
Reply 12, posted (3 years 4 months 4 weeks 3 hours ago) and read 5286 times:

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)
User currently offlineMastropiero From Spain, joined Dec 2005, 125 posts, RR: 0
Reply 13, posted (3 years 4 months 3 weeks 6 days 18 hours ago) and read 5169 times:

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?


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 14, posted (3 years 4 months 3 weeks 6 days 16 hours ago) and read 5079 times:

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."
User currently offlinechuchoteur From France, joined Sep 2006, 763 posts, RR: 0
Reply 15, posted (3 years 4 months 3 weeks 6 days 15 hours ago) and read 5065 times:

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


User currently offlineMiercat From Turkey, joined Aug 2010, 15 posts, RR: 0
Reply 16, posted (3 years 4 months 3 weeks 6 days 12 hours ago) and read 4986 times:

In before lock?

Seriously it's been 10 years, I was 6 when this test came out.



Happiness is V1 in KEWR
User currently offlineMrFord From Canada, joined Jan 2001, 143 posts, RR: 1
Reply 17, posted (3 years 4 months 3 weeks 6 days 11 hours ago) and read 4944 times:

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."
User currently offlinePolymerPlane From United States of America, joined May 2006, 991 posts, RR: 3
Reply 18, posted (3 years 4 months 3 weeks 6 days 11 hours ago) and read 4935 times:

NVM I was wrong

Filler
filler
filler

[Edited 2011-04-06 13:07:09]


One day there will be 100% polymer plane
User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1649 posts, RR: 1
Reply 19, posted (3 years 4 months 3 weeks 6 days 4 hours ago) and read 4823 times:

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.


User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 20, posted (3 years 4 months 3 weeks 5 days 12 hours ago) and read 4694 times:

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


User currently offlinecbphoto From United States of America, joined Dec 2003, 1552 posts, RR: 5
Reply 21, posted (3 years 4 months 3 weeks 5 days 10 hours ago) and read 4655 times:

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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ETOPS: Engines Turning or Passengers Swimming
User currently offlineBoeingGuy From United States of America, joined Dec 2010, 3070 posts, RR: 7
Reply 22, posted (3 years 4 months 3 weeks 5 days 9 hours ago) and read 4624 times:

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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