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Bag Of Air

Southwest flew me home from Seattle, last Friday. (Alaska Airlines took me back again, today.)

The early stages of the flight included some fun events involving cabin pressure. Soon after takeoff, my ears had trouble adjusting to the change in cabin pressure. I thought briefly that the environmental control system (or the cabin outflow valve) was having problems. (How embarrassing. “Pardon me, but is there an aerospace engineer on the flight?”) My ears popped, though, and all was fine. (I’ll attribute it to my recent illness.)

The flight attendant, after taking our drink orders, brought around bags of Air Crisps (Nabisco-made crispy baked snacks, or “chips” as Americans call them). The chips must have recently been brought on board, because the bags were quite inflated. They were almost hard enough to use as balls in some sort of weird food packing-based sporting event. Or maybe as floating devices for small children. Because Seattle is at about sea level, and the cabin was probably at about 10,000 feet, there should be almost 5 psi pushing up on the sides of the bags.

This leads to the observation that one’s gastrointestinal system (a bag of a different type) would be doing the same thing, if it were sealed up tight. I have to wonder how much farting goes on as the cabin changes altitudes, and if the release of non-breathable gases is something that ECS engineers should take into account.



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it is something ECS engineers take into account when determining how much fresh air the cabin needs. I remember hearing stuff about it when I was up at Boeing. :)

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