Engine Failure before V1...

[Marcel_MPH]

What if:

let's say we fly a B737.
During take-off an engine failure is suffered before V1. Proper action can be taken to make a safe emergency stop. Now what if an engine failure is suffered during take-off JUST before V1. Before you can even react on the E/F V1 is called... Do you have to continue or can an emergency stop be initiated?

Marcel_MPH

[Speedbird744]

If the Engine Failure occurs at a fraction of a second prior to the PNF calling V1, and the crew haven't noticed the problem due to the shortest of reaction times then I should imagine, you continue the takeoff. But any major malfunctions before v1 and above 80kts it should be an immediate abort.

If an airline pilot could answer this fully though.

[RaTa]

Your decision to abort is made prior to V1, no matter how close to V1 this is.
If you have not made a decision before V1 and have not started the abort process, then you continue. If you don't then there is a very high risk of ending up in the dirt amongst the approach lights. (not pretty)
Anyway that is the theory I've been taught.......fortunately I've only had to use it in the sim! :O

[Alex Whittingham]

That's correct. V1 is the point by which, if you are going to stop, the first actions should have been taken. i.e. call 'Stop!', close the throttles and start to apply the brakes.

The calculations assume an engine failure at a speed called VEF two seconds before V1, the theory being that it takes up to 2 seconds to recognise the failure and start to act.

[B737NG]

On the older types like B707,727,737,747,757,767, A300B4,A300-600, MD80,82,87,88, MD11, F70,100, You are right.
The newer Aircraft like A320,330,340, B737NG,744,777 you have a acoustic and optic alert, EICAM / EICAS message that recognizes the diffrences in N1/EGT/FF/EPR and alerts the crew to shorten the recognition time and the reaction time. Before V1 remains the same = ABORT the T/O. After V1 if you abort the T/O then the chance is high that you end up in the mud and the opposite approach lights are severly dameged as well as the hull. After V1 it is safer to go and then return to the field. That is why you also require a T/O alternate if the field is below CAT I. If you decide to abort the T/O after V1 you will have a lot of to explain..... In a SIM-check that is usualay a failure of a P/C as the risk management is badly handeld, even if you manage to stop before the end of the RWY. Any futher question?.

NG

[john_tullamarine]

Useful to keep in mind that

(a) the 2 second thing (FAR 25 A/L 42 as the memory prompts) doesn't necessarily apply to older aircraft.

(b) it's been standard for quite a few years (as noted in previous posts) that, in the event that you haven't started some serious stopping by V1 .. then the decision is programmed .. you keep going. This need not necessarily be the best solution in all cases but, on the balance of probabilities, is probably the best all round risk management approach to the takeoff failure problem.

[Chimbu chuckles]

V1, as mentioned above is NOT decision speed...its decision made speed/first braking action taken speed.

One airline I used to fly for, operating F28s mostly from limiting runways (very), encouraged the Captains to remove their hands from the thrust levers 5-10kts before V1. This was to ensure people were 'go' minded at that point and to remove the risk of snatching the thrust levers closed in fright after a loud bang. If you try to abort a few knots prior to V1 then you will almost certainly exceed V1 before you actually start to decelerate.

When I was CP/C&T at a Falcon Op I encouraged the same in my Captains.

Where I fly now (B767s) the company uses wet V1 always and this reduces V1 by about 10kts thereby building in a little buffer at the expense of screen crossing height at DER...only has to be 35' but is virtually always (on 2) approaching 1000' on the typically 12000' runways we operate from. The reality would be far in excess of 35' even if we lost one just before the wet V1 so the Captain removes his hand at the V1 call.

Chuck.

[john_tullamarine]

Chuck ..

Except, perhaps, from a short runway .. where Vmcg might come into play .. and you might never get to the end of the runway in the event that Vmcg is ignored ?

[Chimbu chuckles]

JT exactly correct...Vmcg is certainly stressed if we find ourselves in the PI section of the QRH. Not an issue at LHR, DXB, BNE, FRA, BKK, MNL etc though. I'm sure if we start operating somewhere short enough for Vmcg to become an issue we'll get a modified SOP for that place.

Without grabbing my QRH I seem to remember that Vmcg, in the 767, only becomes a consideration at very low weights. That being the case it's simply a matter of making V1=Vmcg (max thrust). Have to be a pretty short runway though.

Vmcg was so low in the venerable old Fokker that it was hardly a consideration when launching from Madang, Goroka and Mount Hagen...were a few other consideration though:uhoh: :)

Chuck.

[john_tullamarine]

.. F27 .. I have to pull out old pix to remind me what it actually looked like .. but some of the best fun was to be had on the old dog whistle.

Now its main legacy is a bunch of dB losses on my audiogram.

[Chimbu chuckles]

Nah...da other venerable old Fokker:ok:

[john_tullamarine]

... kindergarten problem, I'm afraid ... always get my 7s and 8s mixed up.

[Max Angle]

After V1 if you abort the T/O then the chance is high that you end up in the mud It's also worth reminding ourselves that on a limiting runway the reverse is also true. If you are too "go minded" and decide to continue at a speed below V1 you will not have enough runway left to accelerate to VR and get airbourne before running out of tarmac. Not a nice prospect either.

[Flightmech]

B737NG

The DC10/MD10/MD11 has an "Eng Fail" light on the glareshield on the Capts side just outboard of the master caution/warning lights. This system is armed at or above 85% N1 and will activate when any engines N1 differs by 11% N1 or more from that of any other engine. Doesnt answer the "stop or go" question but proves not only the nice shiney new jets have it!!

[lomapaseo]

After V1 if you abort the T/O then the chance is high that you end up in the mud

It's also worth reminding ourselves that on a limiting runway the reverse is also true. If you are too "go minded" and decide to continue at a speed below V1 you will not have enough runway left to accelerate to VR and get airbourne before running out of tarmac. Not a nice prospect either.

Pretty good advice but just to add some shades to this and your decision making. The data shows that even trying to stop succesfully, without damage, at speeds above 100kts is not reliably safe.

In other words 5% of these result in aircraft off the runway. As the abort speed goes up so does the error rate. This however should not imply that at speeds +5 above V1 you will have a 100% chance of failure, but you certainly will be at the very high end.

This also suggests that V1 should be considered a flight decision speed alone.