Killer51883

now not having the book right infront of me but, the definition of V1 is the speed at which if an engine failure occurs, the aircraft will be able to take off and accelerate to a safe climb speed (V2) by reaching 35 feet agl at the end of the runway. this is specifically regarding the performance of the airplane in getting to 35 feet within a set distance (the runway length). This speed by definition has nothing to do with other mechanical failures (ie tires, flight controls, fires). For example when the concord blew that tire, was it smart to take off above V1 and have an uncontrolled fire in the wing? What if the airplane doesnt even rotate at V1 like the CHQ 145 on christmas eve at JFK. They had to abort and thankfully they were at JFK and not LGA. Now im not saying for something stupid we should abort a takeoff above V1. The laws of physics say taking a 30-75,000 pound object at 120 knots and bringing it to a stop will be a tricky situation at best because of all the energy (KE=1/2mv^2). But is it worth adding the potetial energy of gitting a conditionally non flyable object into the air and then adding more energy into the mix. As was said earlier thats where the grey area and the captains pay comes into it.

visceral

I don't agree that this is a situation requiring a Captain's emergency authority. A light indicating an engine fire illuminates at V1. Why would you reject the takeoff?

ryguy

I really think the situation is the key. Know your airplane and know what you are working with. In a SAAB I doubt it would matter very much that he aborted the takeoff. That airplane is never really going to have a true V1 speed anyway. There is no way that a SAAB is going to have a field length limit problem on that long of a runway (unless you took off from an intersection of course). We have V speeds for a reason yes, but in this case the V1 speed is really only there because it has to be at or before Vr.

In the 744 we almost always have a pretty large split between V1 and Vr. In my airplane there is no way I would abort above V1. The end of the runway is coming up awfully fast!

Thedude

The Tradewinds accident is exactly what happens when you abort after V1. They had 3 good engines but still aborted well after V1.

shackone

What is being suggested in this discussion is that this situation may not be one where hidebound responses need always apply.

I didn't say that this situation required the use of a Captain's emergency authority...I said it was a situation where that discretion might be used because of certain parameters (aircraft braking characteristics, runway length, etc).

Because the Captain determines that this is a prudent course of action based on the circumstances.

No one is arguing against the basic wisdom of the convention that says a takeoff should be continued when an engine fails above V1. All that is being said is that this is not always a black and white issue.

As for those who have tossed in the energy aspect, they have missed one little point. It's not unusual for our V1 and Vapp speeds to be similar...energy is energy. Yes, there are other factors such as position on the runway and associated drag of landing flaps versus takeoff flaps...but if we assume that the V1 stopping weight will be similar to the 'return to an immediate landing' weight, then energy issues become less significant. Stopping a 70,000# aircraft going 130KIAS is much the same in either instance.

Lastly, some have stated that a check airman would consider this decision an automatic unsat. I certainly hope not. I've been giving checkrides since 1971...the last thing we need is an evaluator who sees only the 'book' in situations such as this. Too often, however, this is the outcome, and it doesn't serve the interests of the evaluation process or those being evaluated.

xjsaab

Statistically if you abort after V1 you WILL kill people. AllOfTourTraining teaches you to continue why abort? The aircraft is certified to burn and you can elect to do nothing until flap retraction altitude. There's no way I would stop after V1. There is too much documentation of crews take it off the side/end of the runway during a high energy abort.

subicpilot

There are circumstances posted in this forum that would make aborting after V1 a viable option. Never say never. There are exceptions to almost every rule, and the training we receive does not cover all circumstances...

Training gives you the tools to make good decisions. It works most of the time, but nothing takes the place of sound judgment (that statement is probably in your flight manual or operations manual somewhere...)

I have a good friend that rejected below V1 that put a jet in the dirt in the overrun.

And incidentally, who's to say that because you reject after V1 and take it four wheeling, and perhaps injure or even kill someone, that the outcome if you had taken it flying would not be exponentially worse?

I sometimes wonder if my last go-around was really necessary...but then it's always better to wonder that, than to be sitting there amongst the wreckage and know it for certain.

SaltyDog

Correct, and I agree except there are circumstances as I previously posted in this thread that I will Reject for at V1 or if still on RWY: cargo compartment fire with known dangerous goods that could logically aggravate said fire (ala Valuejet) with TO alt required, good runway environment (dry, flat etc). Will take my chance ala the Tradewinds 747 off RWY excursion in the Youtube video also posted in this thread. In that scenario, most probably crash off airport anyway that will often endanger innocent folks. I fly cargo though with more dangerous materials allowed than pax ops.
Still agree with Subic <g>

HercDriver130

NOTHING is absolute.... nor is there a substitute for experience...but then just how many of us have actually experienced an engine fire indication IN THE aircraft....much less exactly at V1......

Certainly a catastrophic failure may deem in necessary to accomplish a high speed abort... but v1 is there for a reason in the vast overwhelming majority of cases..... black and white?..no, but damn near.

Thedude

There is a lot more to the TDX crash than appears in the video. They are lucky they didn't die on that abort. If the ground had not been soaking wet the aircraft would have plunged off the drop-off just past the airport fence. That was a case of why you WOULD NOT abort past V1.