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USMCmech · January 9th, 2005, 22:13

[ QUOTE ]
One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown.

[/ QUOTE ]

On most fully enclosed gear designs the sequence goes like this. DC-8, DC-9, 707, 747, ect.

Slow to Vlo

wheelwell doors - open

landing gear - extend

wheelwell doors - close

The weelwell doors are huge, and can't handel too much airspeed (that they can survive at all is pretty amazing).

After the doors are closed back up, you can accelerate back up to Vle without hurting anything.

We are always finding fatigue cracks on landing gear doors. They are subjected to huge amounts of vibration and stress durring the short time they are open.

The load on the hydraulic pump is the least of your worries. Most systems run PSIs in the thousands, and usually the pumps can produce much more. The actuator or the hardware it is bolted to will bend or break long before most hydraulic pumps meet their limit.

(light aircraft like pipers may be an exception)

Example a while back a mechanic left a ladder in the way of the gear when it was being retracted. The ladder was crusshed like a paper clip and the gear didn't even pause.

January 9th, 2005, 22:13	#10
USMCmech Old Skool Join Date: May 2004 Location: Dallas TX Posts: 1,729	Re: Min Gear retract speed ? [ QUOTE ] One more thing. I was speaking with a seasoned airline pilot (23,000 hours) and he said the difference in speeds was (depending on the aircraft) because of the gear doors...or at least that was the reasoning on the planes he had flown. [/ QUOTE ] On most fully enclosed gear designs the sequence goes like this. DC-8, DC-9, 707, 747, ect. Slow to Vlo wheelwell doors - open landing gear - extend wheelwell doors - close The weelwell doors are huge, and can't handel too much airspeed (that they can survive at all is pretty amazing). After the doors are closed back up, you can accelerate back up to Vle without hurting anything. We are always finding fatigue cracks on landing gear doors. They are subjected to huge amounts of vibration and stress durring the short time they are open. The load on the hydraulic pump is the least of your worries. Most systems run PSIs in the thousands, and usually the pumps can produce much more. The actuator or the hardware it is bolted to will bend or break long before most hydraulic pumps meet their limit. (light aircraft like pipers may be an exception) Example a while back a mechanic left a ladder in the way of the gear when it was being retracted. The ladder was crusshed like a paper clip and the gear didn't even pause.