Hi everyone,

I come here looking for help regarding engine out procedure during the takeoff phase.

 

What I'm wondering is if ENGINE OUT VNAV is modelled in the NGX.

 

Here is my problem:

I fly my take off with LNAV and VNAV modes armed. In the CDU takeoff REF page2, I have the following altitudes: ACCEL HT 3000ft, REDUCTION 1500ft, and EO ACCEL HT 800.

I simulate an engine out at V1.

When I rotate, the FD command bars make me accelerate towards V2 and keep that speed (correct behaviour as per the flght manual, it is not supposed to accelerate towards V2+20 as for a standard takeoff).

Reaching 400AGL, the autothrottle disconnects, and that's when things start going wrong !

The VNAV profiles is not modified, and the aircraft tries to fly the regular VNAV profiles:

-At 1500ft AGL, the n1 reference is automatically moved to CLB (but there is no thrust reduction of course, as the AT is disengaged).

-At 3000ft AGL, it commands acceleration towards 230kt

 

When I go to the CDU CLB page, it is the normal page, and there is no ALL ENG prompt on LSK 4L as there should be.

For that, see FCOM Volume2 pages 11.41.2 and 11.41.3.

 

The behaviour I'm expecting is that at 800ft AGL, the FD Bars command acceleration for cleaning the aircraft.

And I think I read that it is RECOMMANDED to disconnect AT in case of engine failure, but here it disconnects automatically, and I'm completely unable to re engage this.

 

Any help would be appreciated, and from a real life NG driver, even better !

 

Best regards to everyone.

 

PS: if this issue has already been looked at in this forum, apologies, I've honestly spent some time searching, without luck.

V2 to V2+20 is normal. I think V2+20 is more likely where you'll end up on an V1 Cut. The book sounds like it tries to keep you at V2, but I think it'll still push for the faster speed.

 

I don't know if there is some language somewhere that allows A/T during OEI operations, but the checklists all call for it to be disengaged, so I would go with that.

 

The A/T has bunch of variations and parameters that will cause a disconnect. Once it's gone, stop worrying about it. Power settings are pretty easy on the 737. It's the rudder trim you need to watch for.

 

Maybe try selecting an ENG OUT prompt on the CLB page to force VNAV into OEI? It should go automatically, but try it.

 

I'm interested to see what you find. Have fun!

Hi,

Thanks for taking the time to take a first look.

Actually, the V2, V2+20 part of the take off has a normal behavior (meaning it acts according to the flight manual).

That is:

-Regular take off: FD commands V2 until positive rate is established, then commands V2+20

-Engine Out: -if engine failure before V2, FD commands V2

-if engine failure betweenn V2 and V2+20, FD commands the speed at this time

-if engine failure above V2+20, FD commands V2+20

After all the tests I did, it seems that this part is working fine in the NGX.

 

Regarding the prompt on the climb page, first you are right, it should be detected automatically, and this is not working. The problem is that the prompt only gets me to a page suggesting the speed, but it cannot be validated and hence has no action on VNAV. The VNAV profiles remains standard. So I can't even force a VNAV engine out.

 

And regarding the AT problem, I agree with you, the checklists call for it to be disengaged. What surprises me is the fact that AT are disengaged automatically crossing 400ft AGL, which is not normal if I'm correct.

 

Best regards.

For info, I'm hesitating to submit a support ticket to PMDG, but I don't want to bother them with useless things, especially if this has already been adressed, or if I'm simply mistaken.

If someone knows of a post talking about that, or knows that I'm wrong, any heads up would be appreciated.

 

Otherwise, I 'll try next week a support ticket.

 

Regards.

Got the answer from Ryan himself at PMDG.

Here is his answer:

 

We did not model the stuff on page 11.41.2 - this is on the list for additions to the airplane in SP2.

 

Regarding the other stuff however, there is no automatic switching to the ENG OUT modes on the NG's FMC - it's advisory only and you have to manually activate them using the prompts at 6L/6R.

Hmmm that sucks, thanks for letting us know!