Jcooke From United States of America, joined Aug 2003, 81 posts, RR: 2 Posted (11 years 7 months 4 weeks 1 day 11 hours ago) and read 2496 times:
Here's one for the techies:
On my recent flight PIT-LAX the ground crew was prepping the plane for takeoff and they pulled over this rather large cart with a hose on it. I looked at it and it had an exhaust pipe on it. They took the hose and hooked it up to the underbody of the plane and then started pumping what I'm guessing air into the plane at full bore for about 10 minutes. about a minute or two before they shut this off they started up the engines and then disconnected the hose. The engine did make what seemed to be a backfire sound when it started up.
Was this some type of "bleed air" or whatever you may call it to get the engine started? If not, what was it and what does it do?
DAirbus From United States of America, joined Nov 2003, 596 posts, RR: 2
Reply 2, posted (11 years 7 months 4 weeks 12 hours ago) and read 2343 times:
The correct term for the piece of equipment is an air start cart commonly referred as a huffer. There are three types that can be used. The first is a start bottle which is basically a large tank of compressed air. This is usually used only at smaller airports and for smaller planes say up to a 737 in size.
The second one is a jet starter which is less common nowadays. This is a small jet engine which supplies bleed air through a hose for engine start. It is basically an APU with wheels. It is less common because it has a relatively limited output and it makes an incredible amount of noise.
The third type is probably the one you saw being used which consists of a large diesel engine driven compressor providing a source of high pressure air for engine start. These have the advantage of being quieter than the jet starter and can provide more volume and pressure than the air bottle. This is the most common type used today although there are a couple of the older types still around. As the previous post stated, an external source of air must be used for engine start when the APU is inop.
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