NSEU and DDG,
Thanks a lot Gentlemen for your outstanding posts!
At last I got it clear.
The NORMAL PARKING BRAKE SYSTEM is
redundant , as we rely on the pedals locking pins
and the parking brake blocking valve.
The ALTERNATE PARKING BRAKE SYSTEM is not redundant
itself, as it relies only upon the pedals locking pins,
but the whole system IS redundant, as the accumulator pressure will come into play after the A pressure has bled off, even with the airplane sitting dead on the apron.
Great!
As I'm always eager to learn more, let me ask a few little more questions:
1) I now see clearly on the diagram the ACCUMULATOR ISOLATION VALVE has a larger surface area on the A pressure side, so (as explained by
mono), after a few hours the accumulator pressure comes again into play when A pressure has bled below....
what exactly?
Around 1500psi, is that it?
2) At the risk of asking a stupid question:
Parking for longer periods requires the outboard wheels of the MLG to be chocked.
Why the outboard ones?
Thank you again for your valuable help, really appreciated.
LEM