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Old 7th Feb 2013, 14:01
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gAMbl3
 
Join Date: Jul 2010
Location: Mumbai
Age: 29
Posts: 120
ADR 1/3 less than 260 kts with L/G lever down ----> safety valve is open(lets hydraulic fluid pass through it) {take off condition}

ADR 1/3 less than 260 kts with L/G lever up ----> safety valve is still open as there is a 'Self Maintained' logic. {initial climb condition} As soon as ADR 1/3 more than 260 kts the safety valve will close (stop the hydraulic supply) {cruise}

ADR 1/3 more than 260 kts with L/G lever up ----> safety valve will remain close and when ADR 1/3 drops below 260 kts with L/G lever up it will still remain close. It will open only when L/G lever is selected down.{descent condition}


Why would you want the safety valve to stop the gear retraction at this point? this is exactly the situation you are going to be in after lift off (i.e. speed <260kts, LG lever Down), how would you raise the L/G if you didn't have power in this situation?
There is 'Self Maintained' logic for it.


when the MLG is on the ground and L/G Lever is down (and then there is an arrow pointing to the safety valve), and I don't understand if its supposed to be closed or opened, but I'm assuming in this situation you want the safety valve closed and there should be no hydraulic power to stop an accidental retraction on ground.
L/G lever is locked when main gear is compressed. No matter how much force you apply the lever won't go up on ground.
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