Rapid Decompression

Rapid decompression, which recently happened on a Southwest flight, is a situation that requires immediate action by your pilots. The cabin altitude horn sounds in the cockpit when the cabin altitude exceeds 10,000 feet on most aircraft. Other indications in the cockpit include a noticeable pressure differential in the ears, and the cabin rate of climb instrument will show a climb.For more about the aircraft pressurization system, see Cabin Pressurization

Oxygen masks are dropped automatically in the cabin, while your pilots immediately put on their quick-donning oxygen masks. If this happened at a high altitude, which is where your flight will be most of the time, then you can quickly experience hypoxia (low partial pressure of oxygen) and lose consciousness. For more about the oxygen system, see Oxygen System

After your pilots don their oxygen masks, their next immediate action items are to establish crew communications with each other and the flight attendants to help judge the situation. The next step is to notify ATC (Air Traffic Control) of the emergency situation and require an immediate descent to a lower altitude. Descent to 10,000 foot cabin altitude, or minimum enroute altitude (for clearance above obstacles), whichever is higher, is imperative but must be done smoothly so as not to aggravate the situation. Especially because it would be almost impossible to know if there was any other structural failure outside the aircraft, or that possibly if a piece of fuselage came off and hit a control surface (flaps, ailerons, vertical or horizontal stabilizers) or engine.

What can you personally do to minimize injury from a rapid decompression? Obviously, you will almost never know when it could happen. That is why it is important to listen to the safety demo, especially about donning your oxygen masks. While you hear the same thing over and over again, it just takes a couple of minutes to be ready in case the unexpected happens. When you are in a high stress situation, it helps to mentally go over things several times. Then when such a situation happens, it is almost becomes automatic on what steps to do in a timely fashion. The second thing is to always have a seat belt on when sitting. Once again, the recent situations with rapid decompressions were caused by relatively small holes. Obviously, you never know how a hole or tear happens or if it will expand, even if it starts out small.

While investigations continue, the cause of such tears and holes, is of course, of major concern. One common-sense reason can be the "cycles" an aircraft experiences while flying. A cycle is the climbing and descending that happens during one flight. If you can imagine an aluminum can being constantly flexed, contracting and expanding with the rise and fall of cabin pressures inside, then it is easy to see how such a thing could happen. You can see that a tremendous amount of these cycles could possibly contribute to weaknesses along joints or the skin itself. This was determined as a major factor that caused the Aloha Flight 243 incident back in 1988.


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