Expratt From United States of America, joined Mar 2000, 311 posts, RR: 0
Reply 1, posted (14 years 2 months 2 weeks 4 days 21 hours ago) and read 9350 times:
The hole in the tails of 737, 757, and 767 airplanes is the auxiliary power unit (APU) exhaust. On the 727, it is in the right wing. On the 777, it is on the left side of the tail. On the DC-9/MD80, it is on the right side of the tail just over the engine.
Victor Hotel From Australia, joined Aug 2000, 305 posts, RR: 1
Reply 2, posted (14 years 2 months 2 weeks 4 days 17 hours ago) and read 9289 times:
I know about the APU's, and where they are, and what they do, but I am unsure as to how they work. I have a feeling they are a type of turbine(am I correct?), if so what sort and how does it work, If im wrong what is it and how does it work? Thanks in advance.
FBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 3, posted (14 years 2 months 2 weeks 4 days 15 hours ago) and read 9280 times:
Yes,modern APU's are very small jet engines running at a constant speed.In earlier days (read piston engine times) they were small piston engines almost invariably referred to as "putt-putt's".
All output is being used to generate electric power for ground and in-flight use when ground or engine-driven generators are not available.They also provide a source of compressed air for air conditioning and engine start.Some planes do not have APU's,or it may have been an option.SAS DC-8's did not have them.
Exnonrev From United States of America, joined Oct 1999, 621 posts, RR: 3
Reply 6, posted (14 years 2 months 2 weeks 1 day 9 hours ago) and read 9108 times:
The 707 and DC-8 never came from the factory with an APU. A few DC-8s got them when they recieved the CFM-56 conversion, but they had an overheating problem and were removed.
The only 707s to get a factory installed APU were the E-3 AWACS and the E-6 Mercury TACAMO aircraft. The installation is almost identical to the 727. The C-135 series (the real 717) has one installed in left rear cabin just forward of the boom operator position.
AeroGlobeAir7 From United States of America, joined Jan 2001, 586 posts, RR: 2
Reply 10, posted (14 years 2 months 2 days 5 hours ago) and read 8951 times:
The hole you speak of is the aircraft's APU (Auxhilary Power Unit). The APU provides electricity on the ground for the aircraft, for such functions such as engine start, air conditioning, heating, etc.