Originally Posted by
cougar
For a main deck cargo fire, arming the Main Deck cargo fire switch shuts off two packs (2&3), and E/E switches to closed loop. When the Depress switch is pushed, the cabin depressurizes to 25000', and the aircraft descends or climbs to 25000'.
Not only does this starve the fire, but also maintains zero pressure differential on the main deck, with Pack 1 providing a slight positive pressure for the Upper deck. This logic is what keeps the smoke from the Upper deck.
Do you agree with this logic, 'cougar', are are you repeating it from somewhere? You speak of 'don't pull the smoke removal handle', 'starve the fire' and 'providing a slight positive pressure for the upper deck'. By the time you become aware you're on fire on a 744 (especially a freighter, where all you've got are particulate detectors), you've likely got an "overwhelming fire". Those aren't my words, those are the words of the report.
Originally Posted by N571UP Final Report
The growth rate of container fires after they become detectable by the aircraft’s smoke detection system can be extremely fast, precluding any mitigating action and resulting in an overwhelming fire.
There's a
wonderfully frightening video from the FAA showing what just a single Laptop Lithium Ion Battery fire looks like, and how to fight it (water extinguisher if you got it, Halon and then pour water on it if you don't. About 6:20 in shows what just Halon does - and that's all you got in the lower lobes). If you've got a whole pallet of portable devices, or perhaps a whole plane full if you're flying cargo . . .
Anyone who reads the full report will be the better for it.