Originally Posted by
BluSdUp
A What!!??
Never heard of such a system, can you use an example
IIRC, the BAE 125/800 had such a system and the aircraft I fly now, the Global Express, has an “Aux Press” switch that activates the emergency pressurization system who provides an alternate pressurization source for the cabin in the event of the loss of both cooling packs.
However, when the system is used under abnormal situations, you are limited to FL410 because anything above that may require the bleeds to switch over to the high mode creating too much heat.