mistarose

Very good discussion. I have this book called "Professional Pilot" written by John Lowery, I think some excerpts from his book might help add to the discussion.


"It must be emphasized, however, that V1 is based solely on engine failure. It is not designed to account for other failures and malfunctions. Tire failure in particular is a very serious event at high speeds. Thus a reject decision with a blown tire must not be made based on V1. Instead, after a certain point it is infinitely better to continue takeoff than to reject. In addition, with a blown tire you lack the traction needed to duplicate the published Balanced Field Length (BFL)." page 61

"Many Pilots harbor the opinion that it is always safer to continue takeoff if you are anywhere close to V1. Captain WIlliam W. Melvin, Delta Airlines, writing in ISASI FORUM magazine, tells of an airline instructor known for giving pilots with a known "accelerate-go" mindset an engine failure below Vef. This exercise, he states, always ended in a practice accident." page 62-63

FAA advisory circular Draft A.C. 120-62 (September 9, 1994), Take Off Safety Training Aid, cautions against using V1 as decision speed. Instead, V1 is defined as follows:

1) The maximum speed by which a rejected takeoff must be initiated to assure that a safe stop can be completed within the remaining runway ... and stopway.

2) The minimum speed that assures takeoff can be safely completed within the remaining runway ... and clearway, after failure of the most critical engine at a designated speed.

3) The single speed that permits a successful stop or continued takeoff when operating at the minimum allowable field length for a particular weight.


"Many Pilots harbor the opinion that it is always safer to continue takeoff if you are anywhere close to V1. Captain WIlliam W. Melvin, Delta Airlines, writing in ISASI FORUM magazine, tells of an airline instructor known for giving pilots with a known "accelerate-go" mindset an engine failure below Vef. This exercise, he states, always ended in a practice accident." page 62-63

He summarizes on page 69 by saying the following: "The most important thing to remember is that V1 is not decision speed; rather it is a performance speed. Both the accelerate-stop and accelerate-go distances are calculated from V1. Your RTO decision must be made prior to reaching V1, with the first action to reject takeoff occurring not later than V1. Once you have reached V1 accelerating, you have made the GO decision. Remember too, V1 relates solely to engine failure which is statistically rare with turbine engines.

V1 is not "engine failure recognition speed." Rather it is the speed at which, according to Boeing, "... the pilot's application of the first retarding means during the accelerate stop maneuver." In other words, you must be on the brakes at V1.

And, above all, remember that your decision to initiate a high-speed RTO must be because you feel the airplane is incapable of flying.

Plan for every departure based on worst-case situation. This will eliminate both surprises and accidents."

George Dubya

I am glad we are all professional pilots and this is all so crystal clear.

ToiletDuck

Tell that to the concord that went through an apartment building.

When I was at Flight Safety one thing they hammered was that not every circumstance can be covered by a small list of procedures. There are other instances where aircraft would have made it had they not decided to takeoff. In the sim do what you're suppose to but in real life I feel the CA is still the final authority. If you have a couple miles of airstrip in front of you there's no reason you can't come to a stop. You fly in the airplane in and land on smaller strips than that at higher speeds with no problems. Why risk taking off and melting the thing when you know you can easily stop in the remaining distance? You could stop, deplane, and run from the thing before you even got on final to make your landing. Those checklist are made on statistics but that's why robots aren't flying the things. Some circumstances might require alternate actions. I'd rather live to argue it than die with others knowing, "He did everything right there just wasn't enough time".

ExperimentalAB

You oughta be thanking the FnAA for the mess of Aviation Regulation.

flybywire44

... ok?????

FlyerJosh

A couple of points to add:

In my 8 (short) years of flying transport cat aircraft, I have yet to be able to figure out "exactly" how much runway I'm going to need without going to the books. When you're zipping down the pavement at 110+ knots can you really tell if you're going to stop if you hit the brakes?

I've done a high speed abort in the CRJ. It was initiated shortly after 120 knots (a full 28 knots before V1) after receiving a red "Passenger Door" master warning. I'll tell you that the event was something that was quite uncomfortable for me, the rest of the crew and the passengers. I'll also say that we used up EVERY BIT of available runway 1L at IAD (11,500 feet) using heavy braking. It's not particularly something that I want to duplicate anytime soon.

What do you do when your V1 is significantly different from Vr? (In the CRJ I once had a V1 of about 85 knots and a VR of 135 knots- the difference was due to runway contamination and reduced abort stopping capability.)

My former employer, and my current one (after input from myself) call out "V1" 5 knots prior to reaching the speed, in order to allow "decision delay" time. The thought is by the time that the PNF makes the call and it is processed by the PF, V1 has come and gone. At that point, the PF removes their hand from the thrust levers and waits for Vr.

There have been some very valid points made, but at the end of the day, if the airplane will fly when we reach V1 (and after it), we're going flying.

SaltyDog

Good thread, good reading on topic:
http://www.flightsafety.org/fsd/fsd_jan93.pdf

MatthewAMEL

Blindly following procedure can kill you. Exercise your best judgment. That's why you are sitting in the left seat.

I am sure you are familiar with the recent CHQ ERJ abort at LGA that was 6+ kts above V1 due to the elevator controls being inop. That CA did an exceptional job realizing that although they were above V1, there is no way the aircraft was going to become airborne.

That incident prompted the recent AD for the entire ERJ fleet (inspection of both sets of elevator cables).

I have also had a situation in the sim with wind shear on the runway that caused the speed to never build.

Blueskies21

I think everyone has covered this in the "if the airplane won't fly" exemption. Otherwise after v1 you're better off going, as previously mentioned you'll be at a much lower energy level when you come back around for landing. At 120+ knots is not the time to say hmmm...i think....it might be ..... better to.... stop on the runway. now you're aborting from an even higher speed.

sharksrock

Okay:

1) I think that pilots are slowly evolving to become braindead. It's always procedure-procedure-procedure. Gone are the days before all that, when pilots used good judgement...

2) To all the people using the concorde as an example for T/O after V1;
The average takeoff speed of the Concorde is about 220 knots. Considering that the longest runway length at LFPG is about 13,000 feet long, it is a safe assumption that the Concorde would have used the majority, if not almost all of that runway to take off (especially since there was a tailwind at the time of departure).

1 of their engines was completely shut down, and they would have had minimal braking and reverse thrust. If they had aborted the take-off, they would have crashed several major roads, populated areas, and streams.

Either way, there's nothing the crew could have done to prevent the accident. So please stop using this as a valid example.