The people who fell unconscious were not in the cockpit. They were the people in the back...probably moving around (and at highest risk of hypoxia since they are physically active). They also might have been in an area that was not close to a drop down mask.
|Quoting Davescj (Reply 30):|
My question relates to this also, in cockpit are masks worn? Or simply "available" (as in NOT in overhead compartment)? When the masks dropped in the cabin (due to lack of pressure) did a mask drop also in the cockpit? You'd think that'd be a visual (as opposed to auditory alarm) that the problem is pressure, or am I not understanding Xtoler correctly in thinking that the O2 mas is ready -- ie not dropped from the cockpit cieling?
1) Masks are not typically worn by the flight crew unless there is a emergency (i.e. smoke, depressurization). However, on some airlines, it is SOP for the PIC to wear the mask if the other pilot has to take a physiological break (i.e. go to the bathroom).
2) Masks are not the drop type in the cockpit. Masks must be pulled from a container or fastener and swept over the nose and mouth.
3) In a slow pressurization, you have time to react to warnings. For instance, on Airbus aircraft, if cabin pressure exceed 14,000 feet, the MASTER WARNING alarm sounds and the CABIN PRESS text annunciation is shown in the digital display. After the masks in the cabin drop, the PASS OXY annunciation text is also displayed. Some other aircraft, like the Boeing 717, have an actual voice that warns "Cabin Altitude!". Other aircraft are somewhat more deficient, such as the Boeing 737 which has the cabin altitude alarm being the same sound as the "incorrect takeoff configuration" alarm, which may be part of the reason why the flight crew became on the Helios flight.
However, all of these warnings mean nothing if a rapid depressurization occurs. Useful time of consciousness can be as little as 15-20 seconds at 35,000 feet. Ideally, the flight crew should be familiarized with the signs of a rapid decompression so they instinctively reach for the mask without waiting for cabin warning systems to activate. In fact, on the G550, because of the very high altitudes it can fly at, has an "auto descend" feature that automatically activates if there is a loss of cabin pressure.