Question RE: pressurization and aircraft evac
 

I work with ground crew at KDFW. Recently, an incident at Ft. Lauderdale occurred in which a deranged pax forced his way off of Continental flight as it was taxiing to the active. Reportedly, the pilots depressurized the cabin in order for the F/As to be able to open a door and allow the man to leave the plane.

My understanding of newer commercial airliners is that the pneumatic system, when set to AUTO, doesn't begin to pressurize the aircraft until approximately 60+ knots of groundspeed has been reached on takeoff roll. Is it standard ops to pressurize older aircraft at the gate or during taxi?

Also, in the event of an aborted takeoff with a pressurized cabin, does the outflow valve automatically revert to a fully open position or does the aircrew have to manually open the valve to depressurize the aircraft in order to facilitate emergency evac should it be required?

Thanks.

I seem to recall with the 737 that it pressurises as soon as the packs are turned on after engine start to .125psi, and this slightly stiffens the fuselage and stops the doors banging around in their apertures. The automatic pressurisation system takes over, and in the event of a rapid evacuation, it is necessary for the copilot to switch the automatic control to manual and motor the outflow valves open to ensure full depressurisation. The door can still be forcefully opened though. I understand one of our crews on the Berlin flights with a German stewardess who opened the door after a flight, and maybe the wind caught it, but it swung quite powerfully and nearly pulled her out. She stomped up the cabin in a rage, burst onto the flight deck and loudly told them "you hav left ze aircraft pressurised, und I hav been sucked off!" I think they were too startled to even make a joke! While I'm on the subject of old reminisces, another one appeared in the flight deck with the pilots meal tray which had been standing in a small puddle on the galley counter. Not wanting the pilot's trousers to get soaked she asked "I am wet underneath Captain, would you like to feel?"

What was the question again?

Hi,

Thank you for the reply and the information provided.
Apparently, from what research I'm able to do, some fleet aircraft pressurize when the PACKS are set to AUTO and the engines have been started as you mention, while other's don't begin pressurization until takeoff roll (60+ knots groundspeed). I believe both the B767-300 and B747-400 fall into the latter catagory.

If the aircrew were to be incapacitated in an emergency evac situation, again with the cabin having been pressurized on the ground previous to takeoff, would the system logic still fully open the outflow valves with the PACKS left in AUTO postition?

I guess I'm wondering more about the extent of human intervention that is ultimately necessary to depressurize an aircraft in an emergency evac event. As you mention though, the doors should still be able to be forcefully opened with the cabin pressurized at normal levels on the ground.

Thanks again.

Never mind whether it pressurises.....

Hey rainboe, your stories were very rude but ever so funny...... any more???????