Accelerate-go distance, engine failure below V1

[yankeeclipper747]

I know this is an old subject much discussed, but since a reject is only "recommended" with a failure below V1 what if you elect to continue? I think most would agree that there are situations were continuing the take off might be the safer course of action. While sitting in G/S, Most disgree that you can't be assured of getting airborne on the remining runway distance if you continue with a failure below V1. I think you can with balanced field computations ( all things being equal such as no obstacles etc). Am I right or wrong? Help me out here..

[aterpster]

I know this is an old subject much discussed, but since a reject is only "recommended" with a failure below V1 what if you elect to continue? I think most would agree that there are situations were continuing the take off might be the safer course of action. While sitting in G/S, Most disgree that you can't be assured of getting airborne on the remining runway distance if you continue with a failure below V1. I think you can with balanced field computations ( all things being equal such as no obstacles etc). Am I right or wrong? Help me out here..

If you are below VMCg you will go off the side of the runway. If you are above VMCg but significantly below V1 you may very well go off the end of the runway at high speed. If the runway is significantly longer than the balanced field length for the conditions, you may be successful, but you are being a test pilot of sorts.

It's call "decision speed" for a reason.

[TonyDavis]

There is an excellent publication produced by Airbus and FSF titled Flight Operations Briefing Notes
Takeoff and Departure Operations
Revisiting the “Stop or Go” Decision

Well worth the read and will answer your questions

[Brian Abraham]

Groan. SSG again? Don't know why you are asking this question when you claim

As an ex MD-11 driver and current 744 Captain........

Reject is only "recommended"? Please, who do you fly for so I can give you a miss.

[Teddy Robinson]

ELGC, vmcg 89kts, V1 F33 103kts . Bang at 95kts .. You stop. Bang at anything less than 89kts you stop, bang at 102.99kts you stop. Bang at 103kts you go. It is not really that complicated, though a MS flite-sim might behave a bit differently ? dunno ... never tried one.

[TonyDavis]

How about engine surging 5 knots below v1 on field limited take off gross weight?

God I must be bored tonite:)

[stilton]

Five knots below V1 ?


By the time the failure has been called and reacted to you are past it and in that case you should continue.

[frontlefthamster]

I'm surprised no one has yet mentioned that other than in limiting cases, there is a range of values of V1 which are equally valid for a given takeoff.

For simplicity, the line pilot is only given one value.

There are plenty of good books which explain performance - Swatton's is perhaps the one to put in your flight bag.

To answer the OP's question succinctly: if you are above the minimum value of V1 for your case, you may go, and you will meet the relevant requirements; if you are below the maximum value, you may stop, ditto.

On some types, and in some cases, the range may be very wide.

The practical challenges are as you would expect: if going at V1 min, directional control is the challenge, at least at first, and if stopping at V1 max, then you may be stopping in the limiting case, so the RTO must be executed correctly or an overrun is probable.

[aviatorhi]

Expanding upon the last post, depending on how much authority/responsibility your outfit give you, you may be able to look up your V1min V1max values.

IMHO when I'm dealing with particularly short runways or contaminated conditions it's best to evaluate all these factors and how they effect you for that particular takeoff and come up with a V1 speed which makes you comfortable, so that V1 actually "means" something other than "we'll probably stop before the end" (I know what the math says it means, but in reality it sometimes comes up with it's own meaning).

[CaptainProp]

Most performance software gives Min V1, Max V1 and optimum V1. You pick the optimum and STICK to it. Bang before said speed - Stop(!). Bang after said speed - Go(!).

Simple as that. Then you go home and have a beer.

[yankeeclipper747]

SSG? Spoken by a true armchair pilot

[FE Hoppy]

https://lh3.googleusercontent.com/-itG1mV8eMuI/T1CkVtzcjzI/AAAAAAAAABU/PkT_El3j10Y/s640/V1.001.jpg


My idiots guide to V1

[bubbers44]

If you really don't think you can stop with a failure slightly below V1 throw the rule book out and select a higher flap setting for takeoff. It might be illegal but might get you in the air. Same with wind shear just short of V1, if you follow the legal procedure and abort because V1 was never attained you might run off the end. If you select another notch of take off flaps you will probably make it but if you don't you are in trouble. Which would you select?

[mutt]

Which would you select? I would calculate the figures based on that other flap setting, if they didn't work out, I would go back to the hotel. I have no desire to be the center of an internal investigation that would ground me for at least the next 6 months, so the idea of It might be illegal but might get you in the air. is pure garbage.

Mutt

[italia458]

V1 should be the speed at which the pilot makes the first action to stop the airplane. It really isn't a 'decision' speed. If an engine fails at V1 it's an automatic go. If the engine fails at 2 kts before V1, it's an automatic go. Generally, the decision and action time is 2 sec and accelerating at 4-8 kts per second will require a 8-16 kt 'decision speed' below V1.

It's not that simple all the time. There are scenarios where you would want to reject the takeoff after V1 and scenarios where you'd want to continue the takeoff below V1. As mentioned in a previous post, I highly recommend reading that Airbus document on the Stop or Go decision.

As for the V1 being the action speed, you should read the FARs on that, specifically 25.107(a)(2) and 25.109(a)(1)(ii). You should realize that your aircraft is certified to be able to safely stop using V1 max if you are actually applying brakes at V1. Some companies have compensations where they reduce V1 so that it sort of becomes the actual decision speed so make sure to check which way your company determines V1.

[TruthShouldMatter]

Well if you teach SOPs, basically 'don't think, just do' approach to flying, then the answer to go or no go is going to be a rote memorized company specific, one size fits all approach to this situation. Lead to pilots flying the unflyable because they had V1, or guys stopping prior to V1 maybe in a war zone because they 'got a light'.

So a person culled out of the thinkers, to 'follow orders' now pondering 'what if' is in a pickle, pondering the validity of doing what the company doesn't want him to do.

Before we even get to 'what if', I would ask if your even allowed to deviate, make a decision, can actually act as PIC, etc etc.

[italia458]

Well if you teach SOPs, basically 'don't think, just do' approach to flying, then the answer to go or no go is going to be a rote memorized company specific, one size fits all approach to this situation. Lead to pilots flying the unflyable because they had V1, or guys stopping prior to V1 maybe in a war zone because they 'got a light'.

I think you should re-read my post...

[TruthShouldMatter]

Sure, I get the possibilities...

I merely make the point that on this forum where most of these guys can wax philosophical on the subject, few are given the authority and latitude to make a decision, but more to the point, the thinkers in the group were culled out in the hiring process.

But yeah...if on the roll, I take small arms fire, get some lights and such prior to V1..I could stop and get my head cut off on the internet or I can go.

You'd be surprised how many guys will default to what they were taught and get their heads cut off. That is really what we are talking about here...the culling process is so strong, many of these guys don't even have the imagination to cook up a scenario outside of their indoctrinated SOPS.

[italia458]

I'm not sure what 'company' you're referring too but where I'm from, we would like to hire someone with a brain who can do some critical thinking. It doesn't matter how much you teach someone, you won't be able to teach someone every possible situation they could be in. Even if you did, they wouldn't be able to memorize the procedures to a high enough standard that they would be able to perform any of the procedures without having to think what to do. Why do you think we have decision making courses in aviation?

Small arms fire?... Which civilian airline is going to be operating in an area where they have to consider how getting small arms fire will affect V1?

If you're ever worried about what 'the internet' or your friends will think of you when you're flying an airplane, I don't want you anywhere near any of my airplanes.