" Wait 15 seconds after the last manual gear extension handle is pulled "
To give the freefalling gear a chance to lock in the down position.
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The " landing Gear Lever .....Down " why do this ?
1 - To get rid of the Red Gear Disagree lights since the "OFF" and "UP" position acts act the same in the handle logic.
2 - If "A" Hydraulic pressure returns, it will be applied automatically.