The prime minister of New Zealand, Helen Clark, bruised her arm on Wednesday after the door of her six-seat airplane popped open in midflight. Two constables gained control of the door and were able to hold it closed until the plane landed. How’d they do that? Don’t people get sucked out of holes in airplanes?
Only if the cabin is pressurized and the plane is flying at a high altitude. Clark was riding in the unpressurized cabin of a twin-engine Piper Aztec, at only 8,000 feet. Papers flew around, but nothing was sucked out through door of the aircraft. In fact, the prime minister said that air rushed into the cabin after the door blew open.
At high altitudes, the thin air makes it hard to breathe unless the cabin is pressurized. In a jet plane, air from outside passes through compressors in the engines and then flows into the cabin at a higher pressure. Conditions inside the cabin are considered safe when they approximate an outside pressure at 8,000 feet or less. At high altitudes in an unpressurized cabin, pilots and passengers will eventually fall unconscious from lack of oxygen, or worse. This can take about half an hour at 18,000 feet or only a minute at 35,000 feet.
A blown-out door can be perilous for pressurized aircraft at high altitudes. In 1989, the lower cargo door on a United Airlines passenger jet became unlatched at about 23,000 feet. The sudden and explosive loss of pressure tore open a portion of the cabin—nine passengers were sucked out through the large hole, along with their seats and the floor around them.
The year before, a Boeing 737 operated by Aloha Airlines experienced an “explosive decompression” at 24,000 feet. An 18-foot portion of the roof of the cabin ripped off, and a flight attendant standing in the aisle was ejected from the plane.
In general, the more rapid the decompression, the more likely it is for someone to be sucked out of the aircraft. Three factors affect the rate of decompression: The volume of the cabin, the size of the opening, and the difference in pressure between the inside and outside of the plane. Smaller cabins will decompress more quickly than large ones, because the volume of pressurized air is smaller. Bigger holes also speed the process (something as small as a bullet hole might not pose a problem). And large differences in pressure, like those at very high altitudes, can exacerbate matters.
What else happens when a cabin undergoes explosive decompression? The sudden pressure change makes an explosive sound; the temperature in the cabin drops to match that of the frigid air outside the plane; and the combination of pressure loss with sudden cold produces a fog of water vapor. Passengers may experience the air being sucked out of their lungs, bloating of the abdomen, and the onset of frostbite, hypothermia, or decompression sickness. Holding one’s breath during rapid decompression leads to far more severe effects.
Explainer thanks Doyle Peed of The MITRE Corporation.