View Full Version : How long will it last?
Suppose you shut a jet engine down in the cruise how long would the engine windmill if the shutdown was due to the failure of the oil pressure pump? ie there was zero oil pressure and even windmilling there was zero oil pressure.
KISS please.
Rather short with RB.211 series engines.
NO oil prerssure = BIG time troubles.
OTOH, with a shutdown with minimal oil pressure...it can rotate for a rather long time.
As in two hours...minimum.
Old Smokey
24th Feb 2005, 06:08
Hopefully, it will cease rotating as soon as possible for 2 good reasons -
(1) If there's no oil pressure, further damage to the engine will be minimised making it much less expensive to repair,
(2) Windmilling drag is greater than for a stationary engine, thus performance will be better.
Regards,
Old Smokey
Touch'n'oops
25th Feb 2005, 06:54
Old Smokey
I have been taught that a shut down jet engine produces about the same amount of drag whether it is windmilling or not!
Could this just be a case for the low by-pass jet?
But, still I feel a high by-pass jet will have the same results, due to the fact than all shut down jets effectively become sheets of metal face on to the relative wind!!!
keithl
25th Feb 2005, 10:39
You want to "Keep It Simple" 7FF?
Well, the simple answer is, as 411A says, "It all depends which engine you mean". (Me, agreeing with 411A, WIHIH??!)
The engines I have flown have varied between Hours and Minutes with 0 oil pressure, depending on the lubrication system.
FE Hoppy
25th Feb 2005, 11:55
Keithl
How many times do you think we've shutdown an engine in flight. If I had time I would drag out the logbook but as a rough guess i would say 500-1000?
keithl
25th Feb 2005, 12:29
Hallo. mate, how you doing?
Yes, lots I agree, but not for zero oil pressure.
Or are you just letting me know you're there in case I start getting into techy bits that don't "belong" to me !!?
Old Smokey
25th Feb 2005, 13:06
Touch'n'oops,
It's nowhere near as significant as a windmilling propeller, BUT, the windmilling engine is extracting energy from the airstream (Something is making it turn, and energy doesn't come free). The Performance Manuals for various heavies give accountability for the worst case, this being windmilling failed engine/s. (Usually found in the Performance Manuals in association with the offset rudder drag coefficient, which of course also goes along with a failed engine).
I can only believe the books, I've shut down many during test flying, but so far have been unable to make one stop rotating altogether - don't want to thanks!
Regards,
Old Smokey