RELIABILITY OF THE OLD AND RECENT APU's???
Hi,
Just few questions about APU:
Did the recent APU's are less reliable than the old one?
The reason I am asking this question because the APU in B 737 NG is provided (or may be protected to be correct) with 21 automatic shutdowns, compared to 4 for the old APU' (like B 737-200). So I tought that the recent APU's are more prone (may be) to shutdown while trying to save from probable damage during detected APU malfunctions.
Why APU's (even the recent) cannot provide the pneumatic power up to the cruise altitude (as electric power)? I am not talking about full power but reduced pneumatic power with no electric power (load): (at sea level, 60 f) 160 ppm at 60 PSIA.
You may say that air density at high altitudes is low (which is true). But the recent APU's are provided with a dedicated compressor for APU bleed air (load compressor). The old APU's are not fitted with a load compressor if I am not mistaken.
Last question which is not related to the subject (I aplogize):
If the APU is operating in flight (for some reasons) and the APU catchs a fire (in a twin,tri, quad), is this considered as emergency and necessitate an rapid descent or land ASAP (let's say the fire was extinguished).
Any toughts, comments, and feedback are appreciated.
Thank you.