Sign in to follow this  
Guest Ricardo Sevarant

R/W question about 747 cabin pressurization -

Recommended Posts

Hello PMDG People,The PMDG 747 manual details that the 747-400 pressurization system (with PACKS on AUTO), begins to pressurize the cabin when a sensor detects groundspeed at 60+ knots on takeoff roll. I know that the pneumatic systems on some other fleet type aircraft pressurize the cabin as soon as the PACKS are set after engine start.Question: Do later models of aircraft have the groundspeed sensor system for better fuel economy or is this system incorporated for enhanced safety in the event of emergency evacuation (I.E., the aircraft wouldn't have to be de-pressurized on the ground so the flight attendants could more easily open the passenger doors). Thanks!

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Rico...At 65kts, the cabin is pressurized to a pressure equivalent to 50 (fifty) feet below airport altitude. Even if this cabin pressure command wasn't somehow automatically cancelled when the takeoff was aborted, I'm sure the cabin crew are quite able to overcome a hundredths of psi extra pressure on the door.Also, flight crew procedures for evacuation involve the manual operation of the outflow valves to full open to ensure there is no residual pressure.There is a modified pressurization schedule for when the aircraft takes off and has to return to the airport, but so far I haven't been able to find one for an aborted takeoff on the ground. I had a vague recollection of there being one, but it may have been for a different aircraft.Hope this helps.Cheers.Q>

Share this post


Link to post
Share on other sites

Hi there Q:I'm familiar with your alter-ego, so I'm well aware of your professional credentials in providing me with this information :) Always great to see you here in the forums.Thank you very much for the info! I love learning about R/W procedures with these complex aircraft. Cheers,

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this