Engine failure after V1

[teban13]

Hello team,

I was practicing today the procedure during a failure after V1 and found that the behaviour of the IXEG is really hard to control. I have recorded a couple of videos so you can see what I mean. Basically I am failing engine 1 at 123 knots, V1 is 120 and the plane totally rolles to the left, out of the runway. I try to apply full rudder pedal to keep it in the center line of the runway but, until today, I have not been able to do so. 

I am using X-Plane 10 at MPTO, no wind, no rain, configured "ready to fly".

This is the first video where I record from inside the cockpit:

In this video we can see the replay from the outside:

This third video is an actual practice of an engine failure after V1. It is an Airbus but what I want to show is how the pilot applies rudder control and is able to keep the plane flying nice and soft:

 

I appreciate very much your feedback. Greetings!!!

[teban13]

Hi!

Any ideas?

Enviado desde mi iPhone utilizando Tapatalk

[Morten]

I think this is a combination of several things.

- Failed engine goes from full to 0 thrust in split of a second, probably not realistic, more likely would get a bit more time (spool down) in real to correct with the rudder in most cases.

- At that speed there is very little side friction (weight) left on the nosegear (plus x-plane has a friction weakness we call "creep", long story)

- You are using full engine TO thrust (not normally used) which will give the most problems, but it should off course be able to handle that.

- Not sure what your elevator trim was but I assume it was in the green band.

So thanks for reporting it, we might be able to do something about 1 and 2, but this is more Laminar territory, but we will put it on the list of things to look into.

[richjb]

I have to agree with TEBAN, the rudder authority is not sufficient at scheduled V1 speed (scheduled through the FMC).   If the engine fails at V1, the pilot should be able to maintain directional control deviating no more than 30 feet from the runway centerline - that's a part 25 certification requirement.  De-rates lower VMCG and V1 speed, but the same requirement must be met at all de-rates.

I don't seem to have a similar problem with the other X-Plane B737s, namely the stock/ZIBO 737-800 or the FlyJSim 737-200.  Granted, they are different, but I don't Laminar is necessarily the problem.  

I have a set of FlightLink metal/gas cylinder rudder pedals.  I can put a pretty fast hard push when the engine quits.  I can't keep it straight.   I see the same thing Teban is seeing. 

Could the rudder authority be too low for the airspeed near V1 speeds?   Is the Vspeed schedule correct?

X-Plane is pretty accurate with the V1 cuts.  While I have not done them in a B737, I have done and taught them in Lear 45, Lear 35, CL300, and DA2000 simulators.  Even at the lowest authorized V1 speed, you can always parallel the centerline.  Most cases, you can keep it.

Thanks,

Rich Boll

Wichita KS 

 

 

 

 

[Litjan]

Hmm, I just tried again - for me there is enough rudder authority to regain the centerline when an engine fails at V1. (100.000lbs takeoff weight, full N1, V1 at 120 kts for flaps 5).

However I agree that the onset of the yaw is very sudden and I deviate from the centerline too far before I can compensate.

I am unsure what the reason is for this. The physical forces at play seem to be correct, as there is enough authority (for me) to not only counter the yaw, but also enough to steer back to the centerline against the working engine.

It could be that the engine failure in X-Plane is very "sudden" (vs. a more gradual thrust decrease in a real engine failure). It could also be that we are missing the "seat of the pants" onset of yaw cue that you certainly have in a real aircraft, which allows you to react faster/instinctively.

There is also the possibility that recent updates to X-Plane have changed yaw forces (better ground friction) to make the airplane depart the centerline faster.

I will look into tuning this a bit for the next update - we calculate yaw forces while on the ground within our own plugin (bypassing X-Plane, as it´s ground model is still not acceptable for the fidelity we look for), so it should accomplishable with a code tweak.

Cheers, Jan

 

[richjb]

Hello Jan,

Please don't get me wrong.  I think the physics of a V1 cut in the IXEG and in X-Plane are spot on!  In fact, I practice my V1 cuts in X-Plane rather than P3D or FSX because they are so much better.  Level D 767 in FSX was the only addon that even got close to being realistic.  

My issue is not having enough rudder authority to stop the yaw and bring the aircraft back to parallel the centerline, which is the only certification requirement when V1 is equal to V1vmcg, and then only after a centerline deviation of no more than 30 feet.  

I wonder if some of the causes could be the result of the joystick settings.  I have the elevator (pitch) and aileron (roll) stability augmentation set rather high at 75%.  Otherwise, it's too roll and pitch sensitive for me (have a PFC column yoke).  I have the rudder set at 75% but that might be too high?  

Love the IXEG B737 addon!

Rich Boll

 

[Litjan]

The stability setting may very well be your problem. We STRONGLY recommend to run the plane with artificial stability set at 0. It´s not realistic to use artificial stability at all, and in fact it can interfere with controllability (as we may see in this case).

You can play with the joystick response curve if you feel the plane is too sensitive - this would decrease control deflection for a given joystick deflection, which is more what you are looking for. But the artificial stability is a "training wheel" and "instructor is gently holding his set of controls to help" type setting.

Let me know how that goes!

Jan

 

[richjb]

Thanks Jan,

I appreciate the guidance on setting the joystick.  I'm still new to X-Plane, so don't quite know how to tweak it.  

I'll put the stability settings back to zero and test again.

Thanks!

Rich

[richjb]

Hello Jan,

I retested with the stability augmentation settings back at zero.  There was still a very pronounced yaw, but not unrealistic for a sudden engine cut. A rollback may not have been as pronounced, but very good for V1 cut training.  After the initial yaw and full rudder application, the aircraft's yaw corrected back to parallel the centerline with a little left over to bring it back to centerline. Again, what I would consider highly realistic for a sudden engine cut.  I would like to try it on a high, high, and heavy day to see if the yaw is less pronounced.  When time permits, I guess :-).

Thanks for the hint on the response curves.  I dropped the roll and pitch upper and far right level to 80% and then made it linear from the bottom left.  That seemed to address the control response issue.  The B737 doesn't feel like a Pitts....or my DA2000.  I didn't know that existed.  Thanks!

Thanks again for your help!  I'm starting to enjoy X-Plane! 

Rich Boll

Wichita KS

 

[richjb]

Hi Jan,

I've been doing a few more V1 cuts and engine failures just above V2.   I noticed that I do not have enough rudder authority to keep the ball centered and to keep the heading straight.  Looks like I am always in a slight skid into the failed engine.   I know in the Boeing's, your not supposed to keep the ball centered, but rather have it slightly out with the control wheel centered for zero drag.   That said, I still think there is some issue with rudder authority.  

I have all the stability augmentation settings back at zero.  In the response curves, I am using "Linear" response.  However, I noticed that will full right rudder I cannot get the response all the way to 1.0 (far right on the response line)  See screen shot. Could this be the cause of some of my problems?   Any suggestions on how to fix?  I've already recalibrated my rudders in X-Plane.  The left rudder goes out to about 0.93, but the right one only goes out to 0.8.

Thanks for your help!

Rich Boll

 

[Litjan]

Hi Rich,

I will doublecheck the maximum deflection I can achieve with my setup when I get back home, I am currently on the road flying through thunderstorm swept Europe .

In the meantime you can check the DATA OUT display on-screen for flightcontrols. Check the maximum rudder deflection you can achieve, it should go from -1.0 to +1.0

Also make sure that you are above the "minimum control speed air" when you attempt single engine flight and also make sure that you don´t set more than maximum rated thrust.

As ballpark values that should be above 115kts and not more than 90.0% N1

Cheers, Jan

 

[Litjan]

Hi again,

I doublechecked on my computer - I can achieve values for the rudder of -1.0 to 1.0 on the rudder with my setup. It may be that your rudder isn´t calibrated properly if you can only achieve 0.8 and that will certainly hurt your engine-out capability.

I testflew an engine failure at 46tons (130 V1, 141 V2) and was able to maintain centerline on the ground with the engine failed at 125 and then able to maintain heading once airborne with 141kts.

I will try to improve the ground handling a bit during the engine failure - especially the sudden yaw onset is very hard to counter, causing too much deviation from the centerline. I may be able to convince Austin to provide a more gradual decay of thrust instead of full->0 in 1ms.

Cheers, Jan

[richjb]

Hello Jan,

Sorry that I have not followed up with you sooner.  I have installed Ver 1.3.  I watched your briefing video as well. 

First, the V1 cuts are much, much better.  It makes me look good again as I get ready from my CL300 recurrent next week. 

Second, the new cockpit changes look stunning!  This is hands down the best add-on for X-Plane.  I'm enjoying flying it. 

I look forward for the next version.

Thanks again for addressing the V1 cut issue.

Rich Boll

[Litjan]

Hi Rich,

thanks for the feedback and the nice words!

Cheers, Jan

 

[richjb]

Hi Jan,

I did notice one thing with the experimental flight model.  When applied enough rudder to center the ball following an engine failure on takeoff (V1 cut) and started to climb out, with ball centered, opposite aileron was needed to level with wings (i.e., the aircraft was cross controlled).  With the normal model, this was not the case.  I could center the ball and hold the wings level without opposite aileron.  And, this was not exclusive to IXEG, but I also experienced in while the ZIBO 738, but with the ZIBO I also had a V2 speed that was right on low speed stall cue.  So something wasn't right there. 

I know that Boeing's FCTM says that the pilot should apply enough rudder to center the control yoke with an engine failure.  Pilots should not try to center the ball or skid indicator as doing so would cause a cross control situation and extend the opposite wing's spoiler, which with an OEI climb would not be a good thing.  My question is whether the experimental flight mode in X-Plane is actually modeling this behavior correctly or not?  Is this intentional in the design of IXEG? 

I still fly the business jets, like the CL300.  The "Big Blue" training provider still teaching wings level and ball centered after for engine failure climb out.  Yet, in the CL300 sim, I notice that I'm cross controlled and I bet that I have some spoiler extended. This is also what Bombardier teaches in their FCOM training manual.  There is nothing in Bombardier's FCOM pilot procedures that cross control could cause spoiler extension and loss of lift.  It am now very curious about that.  I'm in CL300 recurrent next week and maybe I'll a few V1 cuts with having the ball 1/2 out of center?

Anyway, I was wondering if you noticed this as well in the IXEG and whether this is still a fluke with the experimental model, or whether this is intentional.  It looks like it might model the Boeing FCTM instructions. 

One other things.  For control sensitivities, where do you set the sliders?  Are they full to the right - full realism, or do you move them to the left a little bit?

Thanks again!

Rich Boll

Wichita, KS

 

 

[Litjan]

Hi Rich,

we don´t really model anything here - it is simply the X-Plane flight model.

That being said, it is correct that in stable, coordinated single engine flight you would normally need both rudder and aileron to counteract the yaw and (since the rudder is not on the centerline of the aircraft but extends above it) roll.

The correct technique, however, is to fly with ailerons neutral, so you have full aileron capability in case you need it (crosswinds) and also to avoid the roll spoilers extending (increased drag). If you fly like this, the aircraft will not be in coordinated flight (the nose is not pointing exactly where the airplane is going) and the ball will not be centered.

You can alleviate this a bit by "holding the hurt engine up" - this way the plane is still uncoordinated (ball not centered), but the nose will point in the direction of flight...this is what is being taught in twin props, because here the performance in a OEI situation is so much more critical.

So in conclusion - push the rudder until the plane stops rolling around the longitudinal axis - then steer the plane´s direction by using the ailerons as you normally would...accepting the ball not being completely centered.

Cheers, Jan

 

Edited July 5, 2020 by Litjan

[richjb]

Thanks Jan!

I appreciate the insight on X-Plane and the roll!

Rich