engine failure with speed above v2

[trommel]

If you suffer an engine failure when your speed is at a point above V2 i have been trained to maintain that speed rather than reducing back to V2.

i have spoken to crew from other operators who have been trained in this way but cannot explain why, there is probably a really obvious reason (which has escaped me) for this, can anyone explain why??

Thanks T

[Jetstream Rider]

There was an accident a few years ago (Chicago? DC10? not sure) where the engine failed on departure due to damage to the aircraft (think it hit something, not sure memory a bit hazy). The flaps and slats were damaged too. In reducing to V2, control was lost of the aircraft and it crashed, the reason being that the wings were not the same shape anymore. Maintaining the speed they had would probably have meant the aircraft could still fly. I think this is one of the reasons for changing the procedure to maintain current speed.

Also, in reducing to V2, if you inadvertently go a bit slower you are very close to losing control even in a perfect aeroplane - maintaining the speed you have maintains control and gives an extra margin.

[PantLoad]

So....What does your SOP say about this?? Have you looked, or have you simply asked your co-workers and esteemed captains?

(When you compare opinions from 'esteemed' captains...then, compare what the SOP says...you'll find the captains aren't so esteemed afterall.)

Read your SOP, then post again!

PantLoad

[Slasher]

Depending on your aircraft-type and SOP, the usual
practise is to hold the speed you've got up to a max of
about V2+15. A very small increase in overall gradient is
achieved at V2+10.

What the "esteemers" are gettin at is the predictions of
the pre-calculated 2nd segment net TO flight path, esp if a
curved TO is necesary during it. The curved splay though
takes into account any V2+ speed. Certainley Id come
back to V2 to reduce the turn radius if a wackin great hill
was looming in the winscreen.

I think John Tulla would be the expert here.

[AirRabbit]

Essentially, Jetstream Rider has it correct. It was Chicago and it was a DC-10. The engine didn’t actually fail, per se. The problem was the manner in which the mating and de-mating of the engine to the wing was accomplished – a fork-lift truck was used instead of the approved procedure, and it damaged the attach points between the engine and the wing. When the airplane rolled down the runway for takeoff everything was going fine; however, at rotation, more stress was placed on the engine attach bolts. The rear attach bolt failed and allowed the rear of the engine to drop down, actually pivoting on the front bolt(s), slinging the engine up and over the leading edge of the wing, tearing out fuel lines and hydraulic lines in the process. The engine departed the airplane – so the term “engine loss” took on a whole new meaning. With the rupture of the hydraulic lines, the pressure in those lines (that was keeping the leading edge flaps and slats held in the extended position) was lost and those devices retracted. The speed that the airplane had achieved was probably sufficient to maintain aileron effectiveness sufficiently to counter the roll - where the roll was caused by yaw due to the asymmetric thrust and the asymmetric lift with the absence of the leading edge devices. As the airplane slowed down to V2 speed, this aileron effectiveness lessened and the pilot was unable to control the roll, resulting in a nose down, rolling impact just off the airport property.

[OPEN DES]

It's as Slasher said.

After a typical N-1 you would want maximum gradient/angle. Which you will achieve at V2+ a bit (typically 10 to 20). (remember improved climb where V2 itself is increased to increase gradient and thus the climb limited TOW).

If the engine failure occurs when flying V2+10 you will have a better climb gradient than at just V2. In general it is accepted that maintaining V2+10 will give you a better overall climb gradient even though you could exchange the 10kts excess speed for some temporary increase of gradient, which would be perfectly as per the performance numbers btw.



If the engine failure occurs at V2 or below you would obviously not accelerate to V2+10 (or so) because your performance numbers do not cater for this acceleration.

[Intruder]

Theoretically, you COULD exchange the 10 knots decelerating to V2 for a bit of instantaneous climb rate/angle. However, that is complicated by the fact that you have to re-adjust your pitch to ensure you do not decelerate below V2. Since you are well beyond the "worst case scenario" of a failure at V1, there is little reason to bleed off the airspeed intentionally.

[Old Smokey]

Slasher is very close to the mark here. V2min, at 1.2 Vs is, somewhat below the speed for best climb angle, but chosen and commonly used as a trade-off against improved field length performance. The best climb angle speed is typically a little above V2+10, and, if V2+10 has already been achieved, maintainance of V2+10 will achieve the best climb angle. Later generation aircraft have V2min derived as 1.13 Vs, and V2+15 is a better substitute for V2+10 for best angle for these aircraft.

An important point to remember is that following an engine failure below V2+10/15, the speed must not be allowed to increase. Using some of the much reduced excess thrust after engine failure for acceleration can only lead to reduced climb gradient, which may be critical if obstacle limited.

Where Operations manuals state that the speed following engine failure should be V2 to V2+10 (or V2 to V2+15), this is not "carte blanche" to operate at will within this speed band. Within this speed band, the existing speed should be maintained.

The overall summary (at least as far as I've written into various Operating Manuals is -

(1) If failure occurs below between V1 and V2, fly the approved pitch attitude to achieve V2, and then hold V2,

(2) If failure occurs between V2 and V2+10/15, hold the existing speed, e.g. V2+7,

(3) If failure occurs above V2+10/15, gently pitch up to reduce to V2+10/15, and hold V2+10/15.

(In the remarks above, the 10/15 would be either +10 or +15, depending upon the aircraft type, i.e. V2 = 1.2 Vs or 1.13 Vs).

In normal all-engines operations, we have the luxury of a large thrust excess, and simultaneous climb and acceleration may be safely conducted. With the much smaller thrust excess following engine failure, we may only use the excess thrust to Climb OR Accelerate, but not both. Certification depends upon this.

Regards,

Old Smokey

[flyboy007]

Presumably because any increase in speed, whether inadvertent or not, will bring you closer to Vx. Therefore should you inadvertently find yourself, engine out (or not) and above your V2 speed, you will then have a better gradient than at V2. True, you would have compromised it by allowing the speed to increase in the first place, but why then bring speed back to V2, and therefore a higher drag speed.

I think.

All the best

[kwachon]

As a former FAA examiner let me give you my perspective and the US definition:

V2, The climb speed is the actual climb speed at 35 feet above the runway surface as demonstrated in flight during takeoff with one engine inoperative.

just a note, It is recommended that you maintain V2 until obstacle clearance has been achieved (400ft if no obstacles) then accelerate to Venr at which time you can then retract the flaps.

[FE Hoppy]

E-Jet FD TO guidance does exactly what Old Smokey describes except its an new cert aircraft with V2min at 1.13Vsr and uses V2+10 as the upper limit.

[john_tullamarine]

Two points to add to OS's comments ..

(a) the gradient vs speed graph is pretty flat .. while the absolute best gradient may be a reasonable bit above V2min, there is no point worrying about it on a simple cost/benefit basis .. the main thing, as he observes, is that you get a comparatively big benefit at little cost if you peg modest margin above V2min.

(b) as another poster observed, there is a consideration with escape procedures. If a turn is included, then the procedure designer will have done the splays on the basis of a min/max V2. As the turn, typically, is to miss a hard bit, you need to make sure that you are NOT above whatever the maximum V2 published with the procedure might be. If there is no published max V2, then look up the V2 for the max published RTOW on the procedure and that is the max V2. If OM SOP doesn't clarify, check with your designers as to whether the turn radius included the V2 overspeed allowance for high weight takeoffs.

OS ... you going to BrizVegas ?

[trommel]

Thanks Guys,

Great explanations, our sops tell you what to do with no explanation, it is nice to know the why behind them

T

[A37575]

Extract in part from the B737 Classic Boeing Flight Crew Training Manual under sub-heading "Initial Climb - One Engine Inoperative>

The initial climb attitude should be adjusted to maintain a minimum of V2 and a positive climb.....if an engine fails at an airspeed between V2 and V2+20, climb at the airspeed at which the failure occurred. If engine failure occurs above V2+20, increase pitch to reduce airspeed to V2+20 and maintain until flap retraction altitude....if obstacle clearance requires a special engine-out procedure and immediate turn is required...initiate the turn at the appropriate altitude (normally at least 400 feet AGL). Maintain V2 to V2+15 with take off flaps while manoeuvring...after completing the turn and at or above flap retraction altitude accelerate and retract flaps.