hydraulics with loss of thrust on both engines (737)

[togatogatoga]

Hi folks..

scenario: high speed flight

both engines lose thrust but continue to windmill.

do you confirm that the windmilling power would allow the engine driven hyd pumps to produce sufficent power to operate gear and flaps?

of course the other option would be to start the apu and connect it on the buses in order to allow the emdps to run..

[aviatorhi]

The pumps fitted on JT8Ds (-100 and -200) are able to provide about 25% of normal hydraulic output when the engine is windmilling, though it isn't enough to swing the gear. Not sure about the CFMs.

[ampclamp]

Windmilling engines will provide hyd pressure.
hyd pressue is achieved very early on even during start. Flow maybe an issue for high loads like flaps but they will work.

[Tee Emm]

Windmilling engines will provide hyd pressure.

Once the IAS reduces below around 180 knots the engines windmill much more slowly and in the simulator this has led to insufficient hydraulic pressure to actuate gear and flaps

[misd-agin]

High speed flight? Why are you worrying about gear and flaps during "high speed flight". Maybe that's the trick part of the question.

My observation is hydraulic pressure is normal as long as N2 is 5-8%. Below that control movement reduces hydraulic pressure. Pressure returns to 3000 PSI as soon as flight control input is stopped.

Three deadstick, no APU, flameout landings in a 737 sim. Flaps and gear operated normally. Maybe slow(too busy to time them) but they worked.

Real world might be different. Good luck. Report back if it ever happens to you. :ok:

[togatogatoga]

thanks for the useful answers guys!