Excerpts from the P-51A, P-51B-5, and P-51C-1 Erection and Maintenance Manual
Relating to the position of inner gear doors and flaps after shutdown

  T
here has been so much discussion about gear doors and flaps on Mustangs, so I spent much of the afternoon studying the Erection and Maintenance manual I have which is a WW II document.  It covers the P-51A, P-51B-5 and P-51C-1 Mustangs.  The long and short is that all these airplanes had identical landing gear and flap systems.  The was a mechanical uplock on the inner gear doors, but it was mechanically linked to the main strut actuator and only engaged when the main gear strut was in the retracted position.  It was held in the unlocked position when the gear was down.  The main gear strut down lock was the only part of the system that remained locked in position when hydraulic power was lost.  It had an internal spring which held it to the locked position, and it required hydraulic pressure to cause it to disengage and allow the strut to retract.  The inner gear doors and the flaps had no other means of staying up than the remaining hydraulic pressure after shutdown.  There was an accumulator in the system but it would not hold pressure indefinitely.  The bleed down rate would depend on the internal leakage of the system, which is usually better on new components than old ones.  I once flew an L-17 in the FT Eustis military flying club that had so much internal leakage that if you tried to raise the flaps before the gear was fully retracted everything just came to a stop until the gear was dropped to the down position again, reducing demand on hydraulic pressure and flow rate.

The page will take a bit to load, there are 9 manual page images.  I did it this way to make it easier to move back and forth between sections.


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