B744F QRH - Main Deck Fire
I see that the revised procedures for FIRE MAIN DECK have been released by Boeing in an Operations Manual Bulletin
Among the changes is this:
"Expedite a climb or descent to 25,000 when conditions and terrain allow. Plan to stay at 25,000 for as long as conditions allow. After the descent has been started, do not delay the approach and landing"
Presumably this procedure is based in part on a 2009 FAA Fire Safety Highlight
"CARGO FIRE CONTROL BY DEPRESSURIZATION"
which compared the effectiveness of cargo fire suppression by depressurization with that of an extinguishing agent (Halon 1301), to wit:
"...Series two test results showed that although depressurization reduced the initial burning, the fire intensity on decent was greatly accelerated. The highest depressurization altitude evaluated (25,000 feet) produced the best initial results but the largest fire on decent..."
Clearly, remaining at altitude for as long as possible before effecting a minimum time descent to approach and landing is indicated
Setting aside for now the very legitimate questions of possible structural damage, or whether an 'immediate landing' (downwind, overweight, off-airport, or ditching) may be warranted, my questions (related to the Boeing OMB and QRH change) are these:
1) Preferred 'min time' descent profile from FL250 to sea level 'clean' or 'dirty'?; that is,
- extend speed brakes and descend at Vmo/Mmo, or
- extend speed brakes, decelerate in level flight to 270K / .82M, extend gear, descend and accelerate to 320K / .82M
and
2) Approximate 'no-wind' time and distance required for each method
I would book some sim time and try it myself, but will be at home on vacation and days off until late in the month
Very interested in to hear your responses and opinions
WIth thanks to all