news article here. Soon after takeoff, passengers heard popping noises, and the left and right cabin walls began buckling inward. After inspecting the damage, the pilot decided to turn around and make an emergency landing.
The cited cause (for now) was a “blown air duct.” Anyone have any further insight? Are they talking about a flimsy duct that was pressurized to some level well above cabin pressure, inflating it and causing the cabin walls to buckle inward? Or was there something else going on?
This is informed surmise; I don’t have any knowledge of the event itself beyond the article you linked to.
The plastic interior you folks see is not structural in any sense. It just hides the insulation and wiring and such behind it. And the none-too-pretty structure of the hull itself.
The interior is made in many separate panels that attach to the adjacent structure. They’re as light and flimsy as possible. And there are gaps between each panel section so as the aircraft flexes the panels shift against each other. It’s about like vinyl siding on a house, but made of non-smoking non-smoldering (i.e. stupid expensive) plastic, not vinyl. And its installed on the interior side of the walls, not the exterior side.
Hidden behind the panels up in the ceiling are large (8" dia) air ducts which take air from the air conditioning supply and distribute it the length of the airplane. The big ducts feed smaller lateral ducts which eventually feed the vent grilles you see at the top of the sidewall. Other similar ducts feed the eyeball vents above each seat.
It sounds like what happened is this: The big duct supply sprung a leak, or more likely a coupling between duct sections came loose. Suddenly a lot of air is being shoved into the space between the flimsy siding and the solid aluminum fuselage structure.
So the result is the “siding” is buckled away from the structure, there’s a lot (relatively) of rushing air noise and enough cold air to keep everybody cool blowing on just a couple of people.
These ducts are flowing air at much higher pressure & flow rate than you’re used to in household or automotive air conditioning. The goal is minimum weight of ducting and minimum backstage volume of ducting. So when a leak does occur, there’s a LOT of fast flow out of the leak.
The total airflow into the cabin is unaffected. So the pressurization is unaffected.
Still not a happy day at work. Time to go land at a nearby airport & get another jet.
But big picture, this is about as big a crisis as driving along in your car and having one of the louvers in your air conditioning vents snapping loose and falling out.
Article including photo of an airplane interior without all the plastic interior veneer, showing the hull and all the stuff usually hidden. (Scroll down a bit to see it.) Photo of John Kerry aboard Air Force C-17 returning from Baghdad.