The canoes are flap-track fairings. Simply an aerodynamic fairing that decreasses the wind resistance around the flap tracks and also protects them somewhat from damage while on the ground. The flap tracks are attached to the wing and to the flaps and are used to make the flaps move. Many aircraft can dispatch without a fairing if one is damaged but fuel consumption will be slightly higher.
APUs are turbines (although before the 60s many aircraft had little piston engines) and run on jet fuel. Simply jet engines like the ones hanging under the wings, but without the fan.
Most APUs provide electrical power for the systems and bleed air for engine starts.
Some more fun APU facts:
- The engine cores on the BAe-146/Avro-100 started life as APUs, for example on the 767.
- 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: View Large View Medium
Photo © Islam Chen
[Edited 2004-08-23 20:35:47]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo