Originally Posted by
Old Fella
A classic example of where blow out panel may have been advantageous is the loss of the JAL B747 which suffered a rupture of the rear pressure bulkhead (due to a previous faulty repair). When the bulkhead ruptured the vertical stabilizer was pressurized and failed, taking the hydraulics to the rudder actuators with it. Total loss of hydraulics resulted which in turn led to loss of control of the aircraft.
I don't see how that would help in this case: a blowout panel for the bulkhead (or anywhere in the cabin) would mean that the cabin can't stay pressurised.
I.e. if the bulkhead blew at pressure difference X: during flight / once you're cruising you're expecting a pressure difference Y that will likely be larger (Y >= X). But to prevent bulkhead blowout you'd need a blowout panel that releases at a pressure difference Z, which has to be smaller than X for the panel to blow before the bulkhead does (i.e. Z < X, and Y >= X). Thus Z <= Y (blowout panel pressure difference less than crusing altitude pressure difference), so the blowout panels go on every single flight.
Note: I'm not qualified as a pilot or an aerospace engineer, I could well be missing something obvious here.