Engine out and yaw / bank effects...

[jcomm 6,056]

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?

 

 

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 />

 

Thanks FLEX and kevin, and, of course my OP wasn't meant to troll the NGX, since it is already one of my preferred add-ons :-)

 

As a matter of fact I just did some tests with the A2A b377 cots, and althought we're comparing apples to oranges, the asymmetry problem is there too. If you clear two engines on one of the sides the effects aren't that big, even without feathering the props!

 

FSX, and hence, Prepar3d limitation IMO... Not a big deal though...

[ichundu 10]

 

 

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!

 

 

 

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

 

Also Vagabondo is a rw pilot, from what i've been reading in these forums

it is good to have such discussions i think, not to discredit a great product, but to point out possible weaknesses so they can get fixed in future sp releases.

[Spin737 102]

 

 

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

I just finished this year's CQ (Continuing Qualification) yesterday afternoon in a 737-700. 3 days in the Level-D sim with a little of everything thrown in.

 

We did engine failures and fires, and you need to keep the plane in trim. You can't have an engine fail and not use the rudder/rudder trim to keep the jet flying. So, if the PMDG isn't acting that way, something is wrong. You should see the "ball" far out of center and the yoke should be displaced until you've got the jet in trim.

[jcomm 6,056]

I just finished this year's CQ (Continuing Qualification) yesterday afternoon in a 737-700. 3 days in the Level-D sim with a little of everything thrown in.

 

We did engine failures and fires, and you need to keep the plane in trim. You can't have an engine fail and not use the rudder/rudder trim to keep the jet flying. So, if the PMDG isn't acting that way, something is wrong. You should see the "ball" far out of center and the yoke should be displaced until you've got the jet in trim.

 

 

Thx Matt for your precious input!  And we all konw that even those LevelD aren't up to the RL experience :-)

 

But what you mention is exactly what happens most of the time in FSX / Prepar3d - almost no "ball" displacement...

 

During initial climb, just after takeoff, it's the moment when those effects are more pronnounced, and that is good to have in the sim, but as soon as your speed builds up, or during an engine failure while cruising, there is no displacement at all...

[Vagabondo 23]

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

For the record I didn't compare one to the other, I was just stating the only realistic simulation I have come across thus far. However, engine out near blue line speed in a Seneca 1 is not a big deal and the rudder force required is quite light. Engine out near the blue line in a Seneca IV (or any other turbo variant) is quite different, the force is significant, very similar to that experienced in a 738.

 

 

Also Vagabondo is a rw pilot, from what i've been reading in these forums it is good to have such discussions i think, not to discredit a great product, but to point out possible weaknesses so they can get fixed in future sp releases.

Thanks Arlind, I agree I don't want to put NGX down, it is an incredible sim. Even with some minor shortcomings, it is still a valuable tool for a RW pilots to practice scenarios and test out ideas. It is that good!

 

You can't have an engine fail and not use the rudder/rudder trim to keep the jet flying. So, if the PMDG isn't acting that way, something is wrong. You should see the "ball" far out of center and the yoke should be displaced until you've got the jet in trim.

I think this is the case that the slip indicator is displaced, but the amount of rudder required to correct this is not very realistic. It is possible to reduce the sensitivity of the control to require more rudder movement to correct the aircraft. However, that is not the only issue with the simulation. In the real aircraft, due to the swept wing configuration and large dihedral effect, if you don't correct at all the aircraft will literally flip on its back (high thrust and low speed) and over correcting causes significant opposite roll, the slightest movement of the rudder pedals can cause significant roll correction requirement. Even with lesser thrust level and higher altitudes, the roll effect with changes of thrust is significant and could easily cause the AP to trip off and end up in an unusual attitude if not corrected with sufficient rudder, yet in NGX, with the rudder in trim for a given thrust and speed, I can play with the thrust with no significant effect on roll.

 

Just for info, realistic rudder trim values are approximately 6 for takeoff, 3 for cruise and 2 for approach.

[jcomm 6,056]

 

 

Just for info, realistic rudder trim values are approximately 6 for takeoff, 3 for cruise and 2 for approach.

 

Thx for the info Vagabondo. These refer to engine out scenarios, right?

[Spin737 102]

Thx for the info Vagabondo. These refer to engine out scenarios, right?

I hope so! If not, the plane needs to be re-rigged.

 

These numbers sound right, but I guess I never look down when I'm trimming the plane. I'm  just making sure the the yoke is level with no pressure on the rudder pedals.

[jcomm 6,056]

Curiously, I just tried these numbers after an "engine cut-off" soon after takeoff and they were close to what I applied.

 

While cruising, taking for instance the default situation for tutorial flight 2, just before TOD @FL390, if you:

 

1) disconnect A/P and A/T and set max throttle and then...

2) shutoff one of the engines

 

A  ) the sideslip cue will stary perfectly centered

B  ) A very mild / slow roll rate will develop

[FLEX1978 373]

I decided to test this, below V2 I cut engine 2 and then left the aircraft to do its own thing, it doesn't behave realistically. I also tested a few other addons and it's the same deal, is FSX really that bad at simulating asymmetric flight? I'm surprised no one has mentioned this before. I still use FS9 for airliner flying and it is simulated correctly.

 

Who needs TAC on the 777, FSX has it built in already!

[jcomm 6,056]

I decided to test this, below V2 I cut engine 2 and then left the aircraft to do its own thing, it doesn't behave realistically. I also tested a few other addons and it's the same deal, is FSX really that bad at simulating asymmetric flight? I'm surprised no one has mentioned this before. I still use FS9 for airliner flying and it is simulated correctly.

 

Who needs TAC on the 777, FSX has it built in already!

 

:-/  Yep ....  :blush: