757 gear alternate extension
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Join Date: Feb 2005
Location: UK
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757 gear alternate extension
Hello to all my fellow pprune's... I would like to know if when extending the gear using the alternate system on the 757 if the gear truck remains in the non tilt position. If so, whats the side affects? and if not, then why not?
Thanks for you answers.
Thanks for you answers.
Join Date: Dec 2006
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I guess the hydraulic pressure from the altn power pack (keel beam right wheel well) also goes to truck positioner. The gear is also already tilted when it comes out of the gear bay.
Gear tilt on the 757 is used for air/ground sensing, that's why I'm pretty sure ther egoes hydraulic pressure to the truck actuator in altn mode.
Gear tilt on the 757 is used for air/ground sensing, that's why I'm pretty sure ther egoes hydraulic pressure to the truck actuator in altn mode.
Join Date: Apr 2005
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The alt gear ext on the B757 uses a small hyd power pack with its own electric motor. This runs for about 10 secs to unlock the gear and doors.
You would use this in flight if you either have a hyd sys failure, or cannot move the selector to down.
If you have a hyd sys failure, there will be no pressure to the truck tilt actuators. This would not be a problem. Truck tilt is only required before gear retraction.
If, on the other hand, you use alt ext with the hyds pressurised (because you cannot move the selector) then when the gear is extending, and the power pack turns itself off (on a px sw) then hyd would be available to the truck tilt.
Well thats the way I read the MM!
You would use this in flight if you either have a hyd sys failure, or cannot move the selector to down.
If you have a hyd sys failure, there will be no pressure to the truck tilt actuators. This would not be a problem. Truck tilt is only required before gear retraction.
If, on the other hand, you use alt ext with the hyds pressurised (because you cannot move the selector) then when the gear is extending, and the power pack turns itself off (on a px sw) then hyd would be available to the truck tilt.
Well thats the way I read the MM!
