Engine out and yaw / bank effects...

[jcomm 6,011]

I noticed that the 737ng, all models, exhibits rather mild effects from an engine out situation.

 

For instance if while cruising I iddle or even shut off  one of the engines, there will be a slight banking into the failed engine, with no hint of uncoordination.

 

Is this true in RL? I even took care to make sure the yaw dampers were disconnected, and the systems page didn't show any hint of rudder either.

 

j.c.monteiro - LPPT

[jcomm 6,011]

Further to my OM, this also applies if I increase the power on the live engine to it's max. There is a slight bank into the dead engine, but no signs of uncoordination (no rudder / rudder trim required).

[WestAir 2,530]

You're saying you don't get asymmetrical thrust issues when you have a failed engine in the NGX?

 

I most certainly do. I can barely taxi on one engine in the NGX, forget about trying a T/O roll or low-speed go-around. In flight, full thrust and no rudder in a single engine situation will cause me to yaw and roll into the ground.

 

In fact, (and someone please feel free to correct me if I'm wrong) the reason the aircraft should roll is because the wing over the dead engine is going to move slower than the wing over the good engine when accelerating without rudder correction. The dead engine wing will gain less lift and "dip" comparing to the good engine wing that will gain more lift and "rise".

 

 

[FLEX1978 373]

That's not normal, however in your case I don't think it has anything to do with the NGX since the yaw effect is even in the default aircraft.

 

To give you a brief example of what should happen, a couple of days ago using another addon I had a engine 2 failure while departing out of Heathrow, I followed all the correct procedures levelled off at the engine out accel alt, trimmed the rudder engaged the A/P and flew the engine out SID. A fair bit of rudder was required however nothing major.

 

The part where I screwed up was on final approach back to EGLL, I was flying on Vatsim and at this point was just focused on getting back on the ground. Ended up doing a dive and drive, cruising down the glide slope with the remaining engine at idle trying to lose speed, at around 300ft (way below stable approach criteria) the remaining engine spooled up to maintain Vref.

 

To say I was taken by surprise is an understatement, as the engine spooled up the resulting yaw and roll was bad, the end result was probably the worse landing in the history of FS, although it didn't register as a crash.

 

Real world I would have been smoking hole in the ground.

[jcomm 6,011]

Thanks for your replies.

 

I am familiar with the effects of an engine-out situation and overall asymmetric thrust on an aircraft, but I find the effect very faint on the 737NG, there being mostly bank (slight), with apparently no uncoordinated flight resulting from it.

 

I thought it might be the yaw-dampers comming into play, but then I made sure they were out of the equation, and also monitored the control deflections on the corresponding ECAM  page before turning off the dampers to check if there was any sign of rudder deflection compensating the asymmetry, but apparently the rudder allways 0º deflection.

 

J.C.Monteiro - LPPT

[Spook 96]

Are your realism setting set correctly in FSX according the PMDG manual?

[jcomm 6,011]

Are your realism setting set correctly in FSX according the PMDG manual?

 

Yes, full realism with no autorudder.

 

Nothing serious, but I would expect that flying with an engine out an the other at max thrust, much more pronnounced effects should come to play.

 

What I see is a slow bank into the dead engine (that's ok), with no hint of sideslip when monitoring the "turn coordinator" cue at the top of the PFD.

Also, now inputs are seen when monitoring the flight control deflections (rudder) on the SYS page of the EICAS.

 

Making sure the yam dampers are OFF I repeated the test, but while the aircraft banks (still at rather low bank rate), there is no hint of uncoordination.

 

J.C.Monteiro - LPPT

[Spin737 102]

 

 

For instance if while cruising I iddle or even shut off one of the engines, there will be a slight banking into the failed engine, with no hint of uncoordination.



Is this true in RL? I even took care to make sure the yaw dampers were disconnected, and the systems page didn't show any hint of rudder either.

Nope, that's not realistic. You're definitely going to see uncoordinated flight and a resultant roll. The roll in this case is more pronounced because of the swept wings, and not so much the induced lift that you might see in a light piston twin.

[Alec 370]

I did a test with my 737NGX setting up a Vr Cut on one engine and I did notice the lack of strong Yaw toward the bad engine. I didn't touch the rudder during climbout, and I did some testing of pitching the aircraft up and letting it loose speed, and as the airspeed decayed, the aircraft became more uncoordinated, but nothing near uncontrollable, in fact, it went to the Red Tape, and all it took was Aileron to prevent the roll and I could easily recover from the situation putting the nose down.

 

I think the FS platform is the limitation here, these developers are doing the best they can to work within those limitations.

[jcomm 6,011]

@Alec: Thx for your test :-)

 

Yes, it's certainly the best we can have in ESP and very good indeed, but I was just trying to find if it was something wrong with my version of the NGX ;-)

 

[Vagabondo 23]

Asym thrust in FSX is generally weak and very unrealistic but NGX makes the best of a bad thing.

 

FWIW, I recall your nick on the ELITE forums. ELITE Pilot 8, specifically the Seneca, is the most realistic PC simulation of asym thrust I have found - you've been spoilt, that the problem

[jcomm 6,011]

 ELITE Pilot 8, specifically the Seneca, is the most realistic PC simulation of asym thrust I have found - you've been spoilt, that the problem

 

Very true, but there is yet another one :-) - the one on my signature here at Avsim ;-)

 

This being said, this NGX is really a great b377NG simulation, to a level of detail I wasn't aware until I bought and started using it.

 

j.c.monteiro @ LPPT

[Andrea1 6]

Hi.

I find really uncorrect to compare a Seneca (prop aircraft) engine out yaw vs. a Boeing 738 it's uncorrect because you know prop aircrafts have stronger yaw moments due to "prop effect" vs. jet how could you compare that? (and is anyway wong because toy can/should compare two identical things i.e. two B738 software programs..not compare two different things). And.... how many among all of you having wrote about "wrong" yaw effect of the NGX are real B738 pilots who exactly know real yaw effects of the real plane? I've been waiting a comment about a real B738 driver who know real plane...this only could be a correct opinion!

 

Best Regards

 

Andrea Buono

[FLEX1978 373]

Andrea, You don't need to be 737NG driver, or any other type of commercial pilot to understand Vmcg/Vmca and the kind of extreme yaw affects that can result from losing an engine if you don't handle the situation correctly.

 

Anyway, I am pretty sure Spin737 is or was on the NG?

[kevinh 409]

Not always stronger effect in a prop. If the critical engine fails then the effect is greater. If it's the non critical side the effect is less. The main point here is that thrust asymmetry is a matter of simple physics. This may be a weakness in FSX that PMDG did not put additional modelling in to enhance. The NGX is a fantastic systems simulation but flight handling isn't its strong point.<br />