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F111UPS767
29th Sep 2010, 18:16
As a result of the recent UPS cargo fire, much discussion was had that left me with the following questions. Any ideas?

1. It seems that a major fire in an aircraft will overpower the ability of the smoke removal procedures to be effective in keeping the cockpit from filling with smoke. (The outflow valves are just not big enough to provide an exit for the amount of smoke that can be generated by a significant fire.) Could you provide more information as to the validity of that statement?

2. Speaking for the 757/767, if a runway for an immediate descent to land is not available, the procedure is to descend to FL250 and set up the packs to depressurize the aircraft to starve the fire of oxygen. It was stated on the newsgroup that remaining higher (such as FL350) would result in unacceptable physiological damage to the aircrew even if on 100% pressure breathing. Is that accurate?

3. In performing the Cargo Fire procedure, the 757/767 goes to single pack operation at half flow. Assuming a descent to FL250, how long does that take to send the cabin pressure to 25,000? Would it be helpful to depressurize faster, either by manually opening the outflow valve fully, and/or turning off all packs until attaining the cabin pressure?