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grimmrad
10th Feb 2005, 04:24
As a PAX I am usually flying for visits or for lectures somewhere, I am no professional in the airline buz. Just out of curiosity: I once flew from BOS to PHL (terribly unreliable airport by the way). The take off was delayed as the pilot could not start the left turbine (Boing 737) due to some generator's fault. It needed to be started somehow from the ground (a car came, you can see, I am no pro in any way). When the engine started we finally got on our way, but I (as did other fellow passengers) had one nagging question in mind: this is all nicely working if you are on the ground - but what if, by whatever reason, the engine stalls in midflight... No service car coming there, I guess.
So here is the question: what if (and is there the possibility of an if)?
Thx for your explanations and response

Dr Illitout
10th Feb 2005, 08:54
I suspect that your aircraft had an inoperative A.P.U.
The A.P.U. is a small gas turbine in the tail of the 737 used to provide electricity and compressed air on the ground.
The starters on the main engines of the 737 are powered by compressed air. Without an A.P.U. a supply of compressed air would be supplied from a ground cart. Electricity would be supplied from another cart.
One engine would then be started "on the gate" the ground air supply and electricity would then be removed, the aircraft would be pushed back and the crew would start the other engine useing air supplied from the running engine. This is called a cross bleed start. This is the method you would use to start an engine in the air too.
If you were to suffer a DOUBLE engine failiure, you would then have to re-start the engines by useing the airflow through the engines to do a"Windmill start"!.
The whole "Airstart" proceedure is a pain in the A**e for the ground crews so we try to fix the A.P.U's as quick as possible!!.

Rgds Dr. I.

canyoujust???
11th Feb 2005, 13:24
Can you explain HUNG start?

BOAC
11th Feb 2005, 13:49
Where a turbine engine achieves 'self-sustaining' rotational speed but fails to accelerate to operating speed. Normally accompanied by rising exhaust temperature and requiring shut-down before damage is done.

edited for spooling

Oshkosh George
11th Feb 2005, 19:13
In the aforementioned situation,would they then try again,or is that a 'summon the engineers' case?

BOAC
11th Feb 2005, 20:11
....as they say, OG, it depends, it depends. Perhaps the tailwind was too strong, maybe the starter cut out too early, maybe they started it incorrectly............

Probably a job for the engineers:D