Does anyone have a minimum running time for a typical APU before it is shutdown again?
A previous company used to start the "rocket" approaching the stand and it was running down again within 4 minutes.
I always thought back to my basic aero groundskule which stressed thermal creep and stabilised running conditions and can't help thinking such a short cycle had a detrimental effect on the APU.
The chief trainer of that outfit would not consider the practice of shutting down #2 on a twin turbofan so's the ext power could be plugged in safely, so we continued to potentially abuse the rocket as it was considered "safer".
