(There has been an issue with the APU enclosure sealant since 2009.) G450: Some G450 APUs cannot normally be operated in flight, even if others can. GV and G550: there are fewer things you can do with the APU in flight. GIV: the APU does a good job of keeping the cabin cool on even the warmest days, so the old practice of swapping the bleeds just prior to takeoff is no longer necessary. The G450 APU is about as good as it gets until you breach the newest generation of Gulfstreams (The G500 and G600), but if you are coming from a GIV, GV, G550, or even another G450, there are some things you need to know about.
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#Ata chapter 49 how to#
There seems to be a wide range of technique and procedure on how to best operate the APU. It burns around 30 gallons of fuel an hour, say about $200, and typical maintenance service plans go for around $50 an hour. The APU generally costs about $250 an hour to operate. It is particular about the way it starts in various conditions, has to be shutdown in a particular fashion, and when things go wrong, it may or may not tell you. What do we care about? The APU takes outside air, fuel, and battery power and converts all of that to bleed air, electrical power, exhaust, and noise. The manuals, Gulfstream and others, all seem to dive into the mechanics of the system and a lot of things that you, as a pilot, don't really care about.
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It works great until it comes time to replace it. The APU is a fairly reliable piece of magic that has a finite life.