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
There 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.
There are 9 manual page images. I did it this way to
make it easier to move back and forth between sections.
