Airliner Pressurization

Airliner Pressurization

Modern airliners are essentially flying beer cans - a thin metal shell made extremely rigid by internal pressure. However, while beer cans maintain their cylindrical form from top to bottom, airliners have sections cut out that are not pressurized, notably for the the landing gear. The cabin floor over those areas needs to be very strong to withstand the considerable pressure exerted on them. 

747 Main Landing Gear Bay

The 747 cabin is 20 feet wide, and if we suppose the main landing gear bay is 20 feet long, then we have an area of 400 square feet. Airliners maintain an air pressure equivalent to that found at 8,000 feet altitude, which is 10.9 PSI (pounds per square inch). The outside air pressure at 35,000 feet is 3.5 PSI. So we have a difference in pressure of 7.4 PSI. Multiply that by 400 square feet and 144 square inches per square foot and we have a force of 200 odd tons pushing down on that floor. That must be a very strong floor.

There was a scene in a movie (Flightplan maybe) where we have Jody Foster as a mother traveling with her daughter on an airliner and the bad guy stashes the daughter in the radome in the nose of the aircraft. Cute, but bogus, since the radome is not pressurized.

Inspired by a line on View From The Porch