Starlionblue From Greenland, joined Feb 2004, 17247 posts, RR: 67
Reply 8, posted (10 years 9 months 1 week 6 days 11 hours ago) and read 8831 times:
That's the great thing about this forum, all the stuff you learn!
Some more fun APU facts:
- The engine cores on the BAe-146/Avro-100 started life as APUs, for example on the 767. APUs are just jet engines although in the 40s-50s some planes had piston powered units.
- The APU for the Classic 747 has 1100 Shaft Horsepower. That's about the same as both engines on the Twin Otter combined.
- The 727 originally only had the APU as an option.
- The 727 APU could obviously not go in the tail so it is located in one of the main gear wells. It can only be used on the ground and is prone to set things on fire. Also, it often creates a tongue of flame snaking over the wing on startup. Pretty good if you want to scare the pax
- I'm not entirely sure, but I think the 737NG APU intake is right under the exhaust:
Nyskymasters From , joined Dec 1969, posts, RR:
Reply 11, posted (10 years 9 months 1 week 6 days 6 hours ago) and read 8440 times:
With regard to the B737NG, there are what appears to be two exhaust outlets. Actually, the bigger "hole" is the APU exhaust outlet while the smaller one is, believe it or not, is a cooling inlet. Just another APU fun fact.
TriStarEnvy From United States of America, joined Jan 2004, 2265 posts, RR: 3
Reply 12, posted (10 years 9 months 1 week 6 days 6 hours ago) and read 8361 times:
Speaking of APU's, there is a really interesting(and very sad) documentary that's on PBS every now and then, about a group of guys who find a lost B-29 that was ditched in a lake. The show documents the planes history, and the back story of the group.
The plane was put down in a fresh water lake, and the corrosion damage was minimal. They spend forever getting it airworthy. As they try and fly it out, the APU breaks loose in the plane, and catches fire. Everybody gets out, okay, but the plane is lost. They show the crew sitting in the snow, and one of them says, something like, "My tools were in there" in such a deadpan way. I swear I just about cried.
If you don't stand for SOMETHING, you'll fall for ANYTHING.
The doors that are open are not the APU doors. They are actually open to allow access to the built-in work stand for the number 2 engine. The hatch on the bottom allows you to get to the stand from below, and the ones on the top allow you to work underneath the engine fan and core cowls. Even more fun are all the hinges to allow you to remove the #2 engine.
Doug_Or From United States of America, joined Mar 2000, 3457 posts, RR: 3
Reply 19, posted (10 years 9 months 1 week 5 days 21 hours ago) and read 7754 times:
Stefandotde- Aircraft only need APUs if there is no air on the ground for starting. It is nice for passengers and crew if there is no electricity, though its not a neccisity. IIRC the DC-8 had no APU, and some BAC 1-11 were also build without (though I couldn't find any pics in the database).
IMissPiedmont From United States of America, joined May 2001, 6361 posts, RR: 33
Reply 20, posted (10 years 9 months 1 week 5 days 16 hours ago) and read 7642 times:
Phollingsworth, you just made me cringe remembering that. It's also the entry to where one goes to inspect the horizontal stabilzer. Instant crush if someone activates the hydraulic system. I hated that little door.
Fun though was the very rare hot start on a 727s APU. Flames leaping out of the right wing 6 feet from a window tended to get the passengers attention.
Musang From United Kingdom, joined Apr 2001, 872 posts, RR: 6
Reply 21, posted (10 years 9 months 1 week 5 days 8 hours ago) and read 7543 times:
Lapper - in the selection of pics of APU intakes, the 146 intake is on the side of the rear fuselage, behind the aft door. So its not visible in that pic. If the intake at the base of the fin caught your attention, thats the ram air intake to the cabin in case air con packs fail.
Tristarenvy - in that B-29 incident, it was an auxiliary petrol powered generator roped to the floor, that spilled fuel on itself and caught fire. I agree though, an immensely interesting documentary and very sad at the end.
CitationJet From United States of America, joined Mar 2003, 2490 posts, RR: 3
Reply 22, posted (10 years 9 months 1 week 5 days 3 hours ago) and read 7458 times:
On the 727 APU operation with flames, there are about half a dozen instances of passengers initiating evacuations on the 727 without the cockpit crew knowing it. When the flames shoot out the APU, the passengers yell fire and open the overwing exits and start climbing on the wing, all while the plane is still taxiing. Check the NTSB accident site.
Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
Mr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 24, posted (10 years 9 months 1 week 5 days ago) and read 7420 times:
Here's two photos to show the difference between the APU exhaust on a 737NG and an older 737-3 as mentioned by Nyskymasters. The 737-3 only has the one exhaust pipe, and the 737NG has both the exhaust pipe & cooling inlet.