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ArjenVdv

Bugs/issues report thread

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On 07/10/2017 at 10:30 PM, downscc said:

Welcome to the PMDG forums.  Please note their rules require our full names on all posts.

The B777 should never use reverse to push back.

Hello, I never saw such rules (nor could I find them while making relevant searches in the forum - perhaps you could help direct me?)

What is it that prohibits a 777 for powerback? (Was speaking to an aquaintance who is a 757 captain and has had to powerback after diverting in an emergency to a smaller airport, and then there was no available tow to push the aircraft out the parking space. It's an unusual procedure due to the FOD risks associated, but I say it is certainly a non-normal procedure that may sometimes have to be carried out in certain circumstances. Is there something special about the 777 in particular that I don't know about that makes this kind of manoeuvre impossible?

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16 minutes ago, XMaramena said:

Hello, I never saw such rules (nor could I find them while making relevant searches in the forum - perhaps you could help direct me?)

 

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19 hours ago, scandinavian13 said:

 

Thanks, not sure how I missed it, but I did.

Amended my signature to include my full name and specs :)

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On 10/13/2017 at 11:47 AM, XMaramena said:

What is it that prohibits a 777 for powerback? (Was speaking to an aquaintance who is a 757 captain and has had to powerback after diverting in an emergency to a smaller airport, and then there was no available tow to push the aircraft out the parking space. It's an unusual procedure due to the FOD risks associated, but I say it is certainly a non-normal procedure that may sometimes have to be carried out in certain circumstances. Is there something special about the 777 in particular that I don't know about that makes this kind of manoeuvre impossible?

Boeing FCOM Limitations page L.10.8. Backing the airplane with reverse thrust is prohibited.

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I guess those GE90s are too powerful a vacuum cleaner to risk high power settings in close proximity to objects in the immediate environment. I don't think you could powerback with just idle reverse.

Is there a diagram i wonder, showing the danger area around the intake for reverse thrust. I found one for the 757 so can only imagine the area for a T7 would be larger.

fig3.gif

 

I did find a T7 digram for takeoff thrust, not reverse thrust which is interesting in that the intake area is only 25ft radius..

777danger.jpg

Never had an issue powerbacking my POSKY! :tongue:

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Hey Nahum, just watched your powerback bug video - I'd say that's quite normal physics happening:-

As you know the thrust reverse mechanism is a bunch of vane which divert the thrust forwards. You've increased the power beyond idle thrust to get the big girl to move back. When you cancel the reverse, the vanes retract, but the engines still take a little time to spool down and are still generating a reasonable amount of thrust. The vanes retract a lot faster than the time it takes for the thrust to decrease, hence the forward acceleration. Just be ready on the brakes! :happy:

It happens all the time with my freeware Avanti - I've just landed and have the props in beta (reverse), move the throttles forward to cancel reverse thrust and she tries to accelerate briefly. 

I respectfully suggest it isn't really a bug. :cool:

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Adding to HighBypass's comments, remember that the core jet is not being reversed on these engines, as opposed to e.g. an MD-80, where the combined exhaust is being reversed. So add to that that you also have positive thrust on the core, you have a closed reverse system, while that huge fan is still spinning down. That is a lot of total forward thrust.

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