Just to add on to this friendly and interesting query and not trying to be a smart Alec but 'shortfuel' is right, there has been a tech bulleting around for a 'little while'.
- Important excerpts and 'updated procedures' only, cause it would take me all week to try and reproduce it all here, hehe.
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'From Boeing Ops Manual Bulletin
Number: JDE-8
Dated: June 15, 2007.
Subject: Engine Flameout Protection
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BACKGROUND INFORMATION
- Boeing and GE have investigated 21 engine flameout events which have occurred on various airplane models since 1991. Investigation of weather flight data and pilot reports associated with these events suggests the flameouts occurred between 11,500 and 33,00 feet in the vicinity of thunderstorms.
- Boeing and GE investigations conclude the event airplanes most likely encountered ICE crystals lifted by convective activity prior to the engine flameout.
-At very cold temperatures near thunderstorms the airplane can encounter visible moisture made up of high concentrations of small ICE crystals.
-These ICE crystals do not cause weather returns.
-These ICE crystals do not accumulate on cold aircraft surfaces.
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OPERATING INSTRUCTIONS
ENGINE FLAMEOUT PROTECTION
Accomplish this procedure when:
- in visible moisture with TAT below -10C near convective weather systems, including thunderstorms, and
- thrust is reduced for a descent or speed reduction.
* * * THE ABOVE APPLIES EVEN WITH SAT BELOW -40C. * * *
PACK HIGH FLOW SWITCH...................................................... ....................ON
(Increases bleed air extraction to improve engine flameout margin.)
NACELLE ANTI-ICE SWITCHES ............................................................ .........ON
(Increases bleed air extraction to improve engine flameout margin.)
Return to a normal configuration when:
the above conditions no longer exist, or
the > ANTI-ICE message is displayed
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For additional info and details, refer to Flight Operations Technical Bulletin 747-400-55,
Subject: Convective Weather Containing Ice Crystals Associated with Engine Power Loss and Damage, dated August 1, 2006.
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Happy contrails, everyone. Cheers!! =)
MC