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B737NG engine fire just below V1

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B737NG engine fire just below V1

Old 15th Jun 2007, 13:20
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B737NG engine fire just below V1

Engine fire just below V1, is it always correct to reject take off?
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Old 15th Jun 2007, 13:40
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If the engine is producing thrust as normal and all other indications are normal, I would continue, shut the engine down at 500' and return to land on the full length of the runway.
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Old 15th Jun 2007, 14:42
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I had thought that the fire bell was inhibited with sufficient margin to allow for either a statistcally safe abort or a statistically safe continuation, without the additional burdens in complicated "what-if" decisions by the crew.
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Old 16th Jun 2007, 04:40
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The fire bell is never inhibited automatically on any aircraft that I know of. It can be inhibited by the crew, but other visual warnings remain.

Engine fire warning right up to V1 is a class A1 reason to reject the takeoff. If you have an uncontrolled fire on the aircraft (and every fire has the potential to be uncontrolled), you have about 3 to 4 minutes to destruction.

Reject! (But not at or above V1)!


Old Smokey
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Old 16th Jun 2007, 05:41
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Strictly speaking you must have initiated a takeoff rejection by V1. But now, if you have an engine fire just below V1 and you abort or reject, you´re doing exactly what you´re supposed to do, exactly what they teach us in the sim, and exactly what the judge will determine as legal.
All takeoffs are "go minded" which means one tends to let the airplane do what the airplane knows best.....fly ! but there are a whole bunch of possible scenarios where one can´t speculate with "oh well I am a few knots below V1, no matter what happens I´ll keep going" because that speed is based on the aircraft´s capability to stop against its capability to be controlled and to accelerate safely for flight. What if you´re taking off on a contaminated runway and V1 is really low, and of course the fire is a REAL fire, and the engine also quits...not the simulator fires, where you only get the bell but the engine performs perfectly... What if you´re departing with anti skid inop...and your V1 is even lower...you decide to continue a takeoff with very low speed, low weight, you might have controllability problems...and may not accelerate, could tail strike and lose control.
All I am trying to say is that you can´t deal in absolutes here. High speed failiures are the probably the most critical scenarios and you can´t just say "I will never reject a takeoff maneuver this many knots below V1 or beyond certain point at the rwy or whatever. Someone came up with a V speed called V1 and your course of action must keep in mind this value.
PS: and yes, old smokey ´s very correct..if its a fire...and you don´t abort, you could have 3 o 4 minutes to destruction, if it was IMC and you had to fly an instrument approach eww..nasty..hope those freon bottles help...

Hey this is my post #100 !!!!!
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Old 16th Jun 2007, 06:42
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How do you know if a warning fire at -10Kts V1 is a real fire?

Better to fight the fire at 500 ft or at the end of the Rwy?

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Old 16th Jun 2007, 07:10
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Even if you had a shock-horror moment on hearing the bell (as most of us would) and actually reached V1 before rejecting, in my opinion that would be the safer option because as old Smokey says, in the air a fire could destroy the vitals in 3 or 4 minutes. Better to go off the end at 20 knots, grind to a halt, get the pax out with a few broken limbs than to be faced with a Concorde-type situation in the air. And really, how often are you really, really stopping distance limited in a B737 from V1? On 25% of all take-offs? Depends on where you operate I suppose. So then we get into the actual odds of running off the end if the reject is actually commenced bang on V1.
At V1 minus 5 or even 10 knots you do not have the luxury of assessing how serious the fire is. You have to assume the worst and do what most briefings state in one form or another - reject for any situation which could make the airplane unsafe in the air. Argue the legalities of what constitutes V1 from the safety of the courtroom, not from the grave.
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Old 16th Jun 2007, 07:23
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So where are you going to stop second guessing the aircraft systems?
As old Smokey posted, if you get a fire warning prior to V1 ...Stop. That is what V1 is for! (+ all your perf. calcs.)
If, (the one in a million) it is false, then you are on the ground no harm done, rather than, "oh it may be false" & the wing falls off three mins after take off!
Or, what would you have done in the unfortunate Concorde accident?
ATC calls "Fire" crew initially had no warning & continue. Had they rejected the take off perhaps some/all would have survived?(remember they had second(s) to assimilate that call before VR ,& they were already past V1)
Where do you start becoming a medium & stop being a pilot?
Hindsight is a wonderful thing after all..........
EDIT..(Gas-chamber & self must have been drinking the same mind altering brew!)

Last edited by Oxidant; 16th Jun 2007 at 12:01. Reason: Didn't proof read my original. So meaning lost!
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Old 16th Jun 2007, 10:19
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Regarding the Concorde:
The warning from ATC came 10 secs after V1.
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Old 16th Jun 2007, 10:42
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The Concorde accident had different causes, but your last posts are really interesting.

Why Rubik101 and many others believe is better to go? Do you want add something else?

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Old 16th Jun 2007, 11:39
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Caveat .. didn't fly the NG only the Classic so my comments have to be generic ..

This is one of those conundrums where you might very well be "damned if you do and damned if you don't" . The correct answer is determined retrospectively by the outcome on the day .... and the Judge at the Enquiry ... if the outcome was less than fortunate on the day ..

As with so many things we discuss in this sandpit ... it all depends.... Certification tends toward the black and white (as it must do ... to be achieveable and repeatable) while the real world is a murky mixture of all shade of greys ..

Things which concern me include ..

(a) the chart accel stop data is based on a fuel cut at Vef .. ie one winding down rapidly and the resulting speed overshoot being contingent upon that very significant thrust reduction

(b) fire warning leaves you with two engines and a significantly higher acceleration (and speed over run .. 5-15kt might be a reasonable ball park figure) while you are going through the reconfiguration from go to stop mode ... ie if the takeoff is seriously accel stop limiting you are absolutely guaranteeing an over run if you stop ...

(c) how far below V1 is "just below V1" when the event manifests itself ? .. considering the particular Certification Basis for the aircraft ...

(d) how long is it since the far end has been cleaned of rubber deposits ? what is the over run like ? what is the crosswind ?

(e) if the runway is not accel stop limiting and has a comfortable margin (bit rubbery until the margin is large) .. then stop

(f) if the runway is accel stop limiting and the over run is nasty .. I'd keep going on the basis that the historicals favour that option on a risk management basis

(g) let's not argue about reverse thrust .. in a real serious situation the maximum effort deceleration is sufficiently high (those who have felt the effect of nosewheel brakes on the 727 will understand what I mean) that the practical effect of reverse is comparatively small in the overall scheme of things.

Of course, we could come up with a few more considerations with a modicum of thought .. but, whichever way you look at it ... it's not a nice place to be.

you have about 3 to 4 minutes to destruction .. which is why some of us push students on endorsements with a contrived minimum time circuit exercise .. engine or cabin fire .. same sort of scenario and concerns ..

.. some days one really should have stayed in bed .. for instance I have a friend who has driven a wheelchair for many years ... having stood in for another colleague on a particular test flight ... same sort of consideration at play .. all one can reasonably do is operate conservatively .. load the dice reasonably to your benefit ... and hope that Lady Luck, on those occasions that she is irritated, visits other people instead of oneself ...
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Old 16th Jun 2007, 11:54
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How do you know if a warning fire at -10Kts V1 is a real fire?

Better to fight the fire at 500 ft or at the end of the Rwy?
Well I know where I would prefer to fight a fire especially with the help of the airport fire crew and that is not at 500 feet!
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Old 16th Jun 2007, 13:45
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"Before 80 kts we abort for any malfunction,
after 80 kts cancel master caution.
Between 80 kts and V1 we abort for severe malfunction, fire, failure or incapacitation."

That would be a part of my emergency briefing.
So basically,
Before V1 = stop
At or after V1 = go
V1 is also normally reffered to as take-off decision speed.
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Old 16th Jun 2007, 16:27
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My understanding is, start stopping at V1 and you go through the fence. (You need to have started stopping by V1). Continue the Take-Off at V1 - 10kts and you cross the fence by 20 feet. Not much, but you cross it. And that assumes total failure of the powerplant.

Of course, runway length is a factor. If you are Vr limited, stop. If you are otherwise limited with a V split, god speed. (Or not speed)

I (on a short runway) agree with coming around for a whole runway, fire brigade in force, low speed landing.

Plus, you have the whole circuit to plan your legal defense.
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Old 16th Jun 2007, 16:53
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you´re not going off the fence if you initiate actions right at V1. An enormous set of unfortunate things should take place for that to happen.
1) improperly executed maneuvers
2) figures not correct (last minute wt adjustments or excess baggage not declared)
3) unconsidered wind changes
4) a performance deterioration factor not kept in mind
5) excessively worn out brakes

Besides keep in mind that for a certain weight, flap, temperature, and wind, V1 is the same in a 6000 ft rwy as in a 12000 ft rwy (except improved climb) so you´re in one scenario you´re not going to go off the fence, no matter what..and the other one you might if things (or you) don´t perform as expected. V1 is generally unrelated to rwy length.....generally.
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Old 16th Jun 2007, 18:09
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1: The majority of overruns happen with two engines producing thrust.

2: Boeing (NG) recommends to abort for fire warnings prior to V1.

In general I would abort.

If runway limited, particular if on a contaminated runway, I would not. Yes, I know all calculations say I'm OK to stop at V1 anyway, but real world is real world, and theory is theory.
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Old 16th Jun 2007, 18:52
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Boeing want you have taken the 1st action to stop no later than V1

With a fire before V1 I will stop. Having lost a friend to an airborne fire I have no desire to take an unecessary risk. Structural failure may occur as early as 4-5 minutes if the fire is uncontained and spreads. I do not practise turnbacks (onto reciperical) mvrs in the sim but I do practise stopping from V1 or below. The sim conditions you to fly a pattern back to land you may not have the luxury of that time as has been tragicaly proven several times.
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Old 17th Jun 2007, 00:50
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It seems that most of you prefer to split between theory or sim (RTO below V1) and real scenario (keep going below V1 if blah, blah, blah).

Personally I agree with John when says "This is one of those conundrums where you might very well be damned if you do and damned if you don't".

Do you think Boeing should spend some
more words about that or the right choice is just related to the pilot's wisdom.

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Old 17th Jun 2007, 03:33
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I would definitely be stopping.....but...

Can anyone recall an engine fire in a pod mounted engine which resulted in structural failure when airborne in recent years? Granted a fuselage fire is something else.

And I'd like to discount the 737-200 and that's a specific installation.
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Old 17th Jun 2007, 04:04
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Sudden Winds,

...makes a good point for me.

On most runways of significant length you can do an improved climb T/O.

The V1 spread may be anything up to 30kts.

On these runways you can reject long past a normal speeds V1 and be assured of a theoretical stop on the runway.

Playing with fire?

I endorse what John Tullamarine says though...the call on the day is going to depend on a number of issues and it may prove to be a day on which you wished you'd never got out of bed.

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