Go/No GO

[skynet737]

ok people.... some more on go/no go decisions
the questions are basically from the point of view of a B737-400 but any views are welcome....
Mr.Boeing says " above 80 knots reject for engine failure, engine fire, or if the airplane is unsafe or unable to fly".

Question is
a.) lets say you get a Wheel Well fire warning at 110 knots( say V1 is 140 knots)... would you reject?
b.) you lose both engine genes at say 110 knots (v1 again 140 knots)... would you reject? (on the B737-400 you now have no Antiskid!)

[ACARS]

Ain't no airline pilot, but what is the point in having V1 speeds if you weren't to stop if an event, like you stated happened anywhere prior to V1?

[m&v]

Where does Mr boeing say this,his mid 90's(FAA sponsored'Go/Nogo training aid)clearly defines the V1 discipline,any fire or failure "recognized and Reacted to" prior to V1 will result in a rejected Take Off.Some Airline constructors put in their own caveats(100knots differentiates an emergency),any recognized??? tire failure means continue as you've nothing to stop with(rims?).80knots is a little low to consider continuing!!!
Boeing ,in their training aid, does have the statistical sucess/failure rate to"justify" a GO descision in the majority of cases.Do you "brief" for the electrical loss/anti-skid failure in your everyday briefings as to a reject,or was the aircraft certified to stop anyway.
Keep it simple(on the limiting runway) if you haven't "recognized/reacted by Vef(v1-1 second,in most cases,or-5knots) keep going!!!
If you haven't got a Vef definition in your flight manual,ask Management to get the manual up to date(1978)

[motions coming on!]

"Where does Mr. Boeing say this" ; in the QRH checklist for a Rejected Takeoff - NNM(although not very clear, it states one should stop for an engine fire below 80 kts, but does not differentiate between different types of fire above 80 kts. Common sense, I know).

[This message has been edited by motions coming on! (edited 21 September 2000).]

[mustafagander]

Question a - no
Whats to burn? There aren't even any possible overheated tyres/brakes in the holes, just a large draft cooling everything off.

Question b - no
On most runways you will be in desperate trouble trying to RTO without antiskid. Do you have HMGs and/or RAT on B737? That ought to enable you to get airborne and sort it out. What else would you lose with no AC power? eg Would the spoilers still work?

[skynet737]

thnx....mustafagander...
nope no HMGs or RATs on the B737... with both engine genes gone you get standby power....u only have standby flight instruments(pneumatic) and no engine indications till you get airborne(when the A/G sensor goes to the air mode)... not a very pleasent feeling on a 550m vis toff. yup the spoilers could be deployed manually.
but as u said the antiskid would be a BIG problem....

[CaptainSquelch]

V1 is only designed for a single engine failure descisions. All the other scenario's are up to you and me but it helps if you realise that beyond it, with all the braking you can do, you may still run out of runway before you run out of speed.

Q a. is simple:
1 - I get a red light right in front of me.
2 - I get a fire bell disturbing the serene silence of a T/O.
3 - I am trained to reject on a fire warning before V1.
4 - I have very little time to look around and decide what kind of fire this is.

I think I'll stop.

Q b. is just a little bit harder. As a PF I am mainly looking outside; especially in a low vis T/O. So with some luck I'll just hear some clicks behind the F/O's C/B panel accompanied by an amber master caution light on the lower end of my view. This will, of course, not cause me to reject. If however I happen to see my complete EHSI gone during a quick glance at the speed, or most of the eng indications missing, or my F/O screaming for help I could decide to stop.

Of course de choices made by Mustafa are the best ones in retrospect. Procedures are not always the best solution for every possible or impossible scenario. They are supposed to be the best average.

ACARS, The point of V1 is that you are supposed to have too little height over the fence at the end of the runway if you lose an engine before it and beyond it you are supposed to be left with too little runway to come to a stop on the concrete. All this is on the assumption that during a reject all the other systems are working (like e.g. your brakes) and after V1 all systems you need for flying are working (like your flight controls). Now the fun really starts if you reject
a) before V1 and find out that this blown tire ruptured some of your brake lines or
b) you continue after V1 and that find out these birds did not hit one but two engines.

Sometimes you win, sometimes you loose.

Sq

[skynet737]

thnx sq for ur opinion....
Q a. i agree with you that there would be little time to figure out wats causing the fire bell... besides on line getting a fire bell before v1 and getting it in the Sim (when ure instructors gone through the days excersises with you in pre brief are two separate things...

Q b. i still dont think id reject.... i think...

thanx all for you're inputs.... :) :)

[quid]

The Boeing and FAA training material is very general. (Trying to keep it simple.) It really addresses the max weight scenario.

I think in a way it's done the aviation community a disservice to some degree. Many pilots are now in a "above 80 kts., I'm going" mindset.

In a great number of cases, we have much more runway than is required to accel-stop. There's nothing inherently dangerous in stopping an airplane from 130 kts or so, we do it on every landing.

Except for extreme weight or density altitude situations, most transport caregory airplanes achieve 120 kts about 3000' into the t/o roll. (Look for it, you'll see.) Now, if I'm on a 10,000 foot runway and I've got 120 kts at 3000, I've got 7000 left in which to get it stopped. NO WAY I'M TAKING THAT FIRE WARNING INTO THE AIR! At 80 knots I've only used about 2000' of the runway.

Even in a balanced field situation, I'd rather go into the mud a little bit at the far end than take a fire with me flying.

These airplanes stop much better than most pilots give them credit for. That's because most have never done a max effort braking stop. If you ever do, you'll know what I mean.

In the words of a wise old pilot, "The weak pilot thinks about the takeoff. The professionals think about the abort. EVERY SINGLE TIME."



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[Two Bars]

Trouble about the go/no go decision is that it can never be reduced to a simple yes/no answer. There can always be extenuating and complicating circumstances.

If the Concorde crew perceived the full nature of their problem before rotate, would they have elected to abort beyond V1 and overrun, or continue and suffer their ultimate tragic fate?

Another case-in-point was a USAF (I think) aircraft that was departing an airfield in Alaska in winter. The Captain aborted the takeoff slightly above V1, overran the runway and the final result was the deaths of about 30 of his 100 passengers. After the event the Captain said that "something just didn't look right". The investigation team subsequently found out that one of his brakes was binding and that he never would have achieved rotate speed - his actions meant the difference bewteen running off the end at 60 knots versus running off the end at 120 knots.

The moral - the answer to the go/no go question is never easy. Those entrusted with this responsibilty have (hopefully) had enough experience such that, when the big test comes, they can make an almost instinctively correct decision.

[Streamline]

Question A: Fire warning before V1

Abort

Question B: dual gen loss during T/O run

Continue

But may I bring up a suggestion ?

Would you land with a braking action repored to be zero and no x-wind present ?

Next time you land a B 737 simply do not brake at all, only use reversers and spoilers you will see, it's not a big deal and will give you a good practical feeling if one day the braking action really gets low.

So in the low speed regime on T/O there should be no problem to abort without anti-skid if you react as on the previous discribed landing roll.

But even then to continue puts the odd's on your side so really continue is still the best option. It flies better than it stops without the anti-skid.

And flying on the standby instruments should be no problem if you earn all that money.

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Smooth Trimmer

[This message has been edited by Streamline (edited 27 September 2000).]

[skynet737]

more great thoughts... thnx twobars(may u get three n four...) and stremline( may u encounter no turbulence!) :) :)

[Streamline]

skynet737

May I bring up to following suggestion

Max X-wind = friction coefficient - 15 it works really well

Example

Braking action medium to good
coef= 0.35
cross-wind = 0.35-15 = 20kts


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Smooth Trimmer