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CFM56 Cool down time

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CFM56 Cool down time

Old 21st May 2007, 17:20
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CFM56 Cool down time

Does somebody know something about a possible min cool down time of the CFM56 engines. I.E.: I used during landing max reverse and the apron is right there and taxying to the spot and engine shut down take less than 3 minutes!

Thanks volks

HPF
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Old 21st May 2007, 17:25
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BA SOPs for CFMs is three minutes after use of reverse and three minutes when max reverse used on IAE engined aircraft.
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Old 21st May 2007, 17:42
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Three minutes after "normal" use of reverse. Only one minute required if reverse was no more than idle.
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Old 21st May 2007, 18:34
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What is the technical reason for the minimum time before engines off?
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Old 21st May 2007, 19:17
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To allow the hot section of the engine to thermo stabilise (i.e. avoid shock cooling I think). I have seen presentation from CFM and they say min 1 minute, ideally 3 minutes to give long term preservation to the engine. Its suprising how many regional airports have aprons close to the runway so the inbound taxi time is short enough to cause it to be a problem.
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Old 21st May 2007, 19:34
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So you may need to take a longer route to the apron or ask for different parking spot in order to cool down the engine?

Rwy in Sight
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Old 21st May 2007, 19:38
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Not just regional airports! Land on 27R and if you get braking right you can be on a domestic stand in a few seconds. Quite embarrassing sitting there with the engines running waiting for our SOP 3 minutes.
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Old 22nd May 2007, 01:11
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That's good reason to (traffic permitting) let the aeroplane roll down the runway to the next exit. The longer taxi back will give you the extra cooldown time.

Of course when ATC says "expedite"...
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Old 22nd May 2007, 02:51
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Oh no CaptainSandL....you are quite incorrect on this one.

I'm here now looking at the current CFM International SOIs, and they tell me that the 3 minutes is to be the normal, following the use of reverse thrust!

No mention of 'normal' or 'max', just reverse.

Taxi time can be used as part/all of this time.

The one minute cooldown time is an unusual once-not-to-often thingy, and is not to be come the norm.
But the one minute is the absolute minimum!

Also, just as an aside, warmup times in excess of three minutes before setting takeoff power, will reduce the maximum peak EGT during the takeoff, which is something we all like!

Cheers...FD...
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Old 22nd May 2007, 03:06
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From my copy of the Boeing Operational Manual, Normal Procedures-Amplified Procedures:-
"If possible, after high thrust operation, including reverse thrust, run the engines at or near idle for three minutes before shutdown to cool the engine hot sections. Time at or near idle, such as taxiing before shutdown, is applicable to this three minute period. If needed, the engines may be shut down with a one minute cooling period. Routine cool down times of less than three minutes before shutdown are not recommended."
CC
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Old 22nd May 2007, 10:28
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Everything you wanted to know on the CFM56-3 (Classic)
PPS 3.5mb.......

Cheers
TOD

http://us.f13.yahoofs.com/bc/4417428...wJsUGBGxm17uPu
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Old 22nd May 2007, 10:31
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That's good reason to (traffic permitting) let the aeroplane roll down the runway to the next exit. The longer taxi back will give you the extra cooldown time.
And/or taxi to the ramp at a nice sedate speed!
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Old 22nd May 2007, 10:32
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The OM for Mechanics is the AMM.
There are two shut down procedures:
Stop the Engine Procedure (Usual Engine Stop)

If you cut off the fuel before wating the 3 minutes cooldown periode you can compare it with a flameout not caused by an engine failure:
Stop the Engine Procedure (Emergency Engine Stop)

So in my (technican) point of view, 3 minutes are minimum.
Shutting down without waiting the whole 3 minutes normally not end in a extreme damage of the engine, but lifetime and performance are reduced.
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