stall
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Engine Failure Between Vr And V2

Thu May 13, 2004 10:00 pm

Hello everybody,

Sorry if this subject has already been clarify but I couldn't find an answer to the following question:

What is the procedure for the crew if an engine fails between VR and V2 ?

From what I understand the rudder won't have enough authority to counter the yaw generated by the engine still producing thrust. I believe that in such configuration the airplane can neither climb nor accelerate due to the additional drag caused by the deflected rudder and ailerons (and obviously the missing thrust of the failed engine).

So what are the options left ?

I remember reading an article about medium bomber (A26, WWII) that stated that the procedure with an dead engine between Vr and V2 was to kill the good engine and land strait ahead. The outcome was always better than trying to fly on one engine at such low speed and altitude.

Thank for your reply.

Stall,

Always fly safely
Flying is fun
 
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TS-IOR
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 10:25 pm


Take-off would be performed because all the speeds and loads have been made with a N-1 (number of engines-1) performance.P/F has then the choice to return to airport or continue the flight.

V1 is the decision speed before which an airplane could be stopped respecting the accelerate-stop distance and beyond which stopping the aircraft,using wheels brakes and spoilers,is a bit difficult.

Make sure that all the pre-flight calculus arede with an engine failure expectation.
 
wing
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 11:02 pm

V1 is the decision speed before which an airplane could be stopped respecting

V1 is not a decision speed.Its the last point where abort should be started.Its too late to decide an abort after V1.Boeing test data allows the line pilots 2 seconds to make a decision for an abort and test data shows an abort 3 seconds after V1 will cause you leave the end of the runway with speed around 40-60 kts.

When a "continue" decision is made with an engine failure after VR the airplane will still be able to reach to a height of 35 feet at the end of the runway.

When an engine fails in the instrument conditions the first indication will be roll movement.First you controll your roll with the aileron input then apply smoothly(don't kick it) opposite rudder.In visual conditions however its easier to recognise the yaw first.

The correct way to keep the airplane under control is apply enough rudder to keep the control wheel centered.(your feet gets used to that feeling after practice)Rudder will be enough to counteract the yaw.Trim the airplane and engage the AP reduce the workload.

As you do your no:1 priority:FLY THE AIRPLANE FIRST, now you can deal with the emergency and start making decisions.
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Jeff G
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 11:04 pm

V1 is always less than or equal to Vr, and at V1, you're committed to the takeoff, so if an engine failed after Vr, you'd continue the takeoff. Not only is there enough rudder authority, there's sufficient performance to successfully take off. Those are all implicit in the V1 calculation. Sometimes V1 is 20 knots or more less than Vr, so in this case if an engine fails on the runway after V1, you'd accelerate on one less engine to attain Vr, and then rotate. The performance is there, but has to be handled correctly.

For a simple engine failure, it would be a terrible decision to cut the remaining engine(s) and attempt to stop on the remaining runway. You'd likely run off the end and wreck a plane that was perfectly capable of flying. Far better to continue.
 
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TS-IOR
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 11:05 pm


Rudder force > 150Ibs no ?
 
SlamClick
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 11:08 pm

Let me correct an apparent misunderstanding on your part.

Your quote: From what I understand the rudder won't have enough authority to counter the yaw generated by the engine still producing thrust.

The speed you are thinking about is VMCG or VMCA not V1 below which the rudder may not have enough authority to counter the thrust asymmetry.

Under US regulations (I'm sure JAA regs are similar) assuming that pre-takeoff performance numbers were correct, a two-engine jet experiencing the loss of one engine after V1 will continue to accelerate, climb through gear and flap retraction and return to the field or proceed to the takeoff alternate safely.

As a practical matter I'd say that from V1 to VR is rarely more than a second or two, and that V2 passes almost un-noticed between the "positive rate" and "gear UP" calls.

Also worth noting, especially for light twin pilots is that VMC (Air or Ground) is predicated on full power/thrust on the operative engine. There are two major factors in the asymmetry of thrust equation; thrust and rudder authority. Climb performance permitting, thrust can be reduced which will decrease VMC or speed can be increased above VMC which increases rudder authority.

VMC is kind of an acknowledgement that at zero airspeed the rudder has zero authority and that it does not gain any until the "Q" or dynamic airload reaches a certain point. Well above that speed, the rudder has enough authority to pop the tail off the airplane if it were moved to full throw. Hence the rudder limiters.

Now as to the A-26, well I don't have much information about it. An old boss of mine flew P-38s during that war and told me about Lockheed's Tony LeVier visiting his squadron to demonstrate engine-out procedures. The problem was similar to that you cite for the A-26. Near VMC they experienced loss of control because of the "excess" power. (Not to mention that the P-38 had two "critical" engines because the props rotated outboard.

LeVier demonstrated that even on heavy takeoffs they had so much excess power that all they had to do was reduce power on the remaining engine, shallow the climb and let it accelerate which increased the rudder authority. Keep it slow and keep full power on and you were probably going to die.

Anyway, VR is well above VMC as calculated under FAR 25 therefore, following procedures will save the day. Procedure is normally to climb at V2 or at V2 plus a small additive speed if you are above V2.

More explanation than you asked for?



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SlamClick
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RE: Engine Failure Between Vr And V2

Thu May 13, 2004 11:20 pm

Wing Boeing's data is for the takeoff which is field-length limited, not every takeoff. Clearly for a light weight takeoff, on an extremely long runway (like the ten miles-plus of Muroc Dry Lake) it would not apply. Still, rejecting the takeoff after V1 is not recommended and is almost certainly less safe than going around for a "normal" non-normal landing.

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wing
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RE: Engine Failure Between Vr And V2

Fri May 14, 2004 12:42 am

SlamClick,

This information was taken from a training video prepared by Boeing company titled:" Stop or go decision"I know speed example may not apply for all take offs,but the 2 seconds time for making decision is what is used for line pilots to to respond since test pilots expect that they will abort the take off but regular line pilot doesn't.

I guess thats an example to make you remember better when the second comes that you struggle to decide weather or not to abort.
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stall
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RE: Engine Failure Between Vr And V2

Mon May 17, 2004 3:27 pm

SamClick, Wing,

Thank you very much for your answers. Very helpful.

Stall
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L-188
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RE: Engine Failure Between Vr And V2

Mon May 17, 2004 4:33 pm

A lot of airplane have ended up out in the mud because somebody decided to perform a rejected takeoff after V1.


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RE: Engine Failure Between Vr And V2

Tue May 18, 2004 6:42 am

Just for info - the '2 second rule' is based on 2 instruments. It takes about half a second to read an instrument, then the same to check it. If you need to check, for example, a back-up instrument, then that also takes 1/2 plus 1/2 second.

Note: I don't know if this is what Boeing used for their calculations, but it is what we have used for similar applications. It is based on visual scanning speed, but I can't remember for the life of me who did the experiments (sorry - it's late here...)
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BMAbound
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RE: Engine Failure Between Vr And V2

Tue May 18, 2004 11:34 pm

To Wing or SlamClick or anyone else that flies twin jets-

What if an 737, A320 or whichever twin lines up on the runway for takeoff and has a 30 to 40 kt cross wind from the right and also loses its right engine? Even with power from both engines, the nose will turn into the wind and I would imagine the yaw as being terribly big if the plane simultaneously loses the engine on the "critical side".

Any special procedures, or just a heck of a lot more rudder to compensate?

Thanks!

Johan
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AAR90
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RE: Engine Failure Between Vr And V2

Tue May 18, 2004 11:42 pm

Any special procedures, or just a heck of a lot more rudder to compensate?

Just a lot of rudder.... which is why the 738 has a 36 knot crosswind maximum "demonstrated" wind "limit." And yes, it does quite well single-engine w/36 knot x-wind.  Big thumbs up
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