After a hole opened up in the fuselage of Southwest Airlines flight 2294 from Nashville to Baltimore, there has been a lot of talk about cabin depressurization and structural failure. The jury is still out as to the cause of this failure, but the incident does bring the topic of depressurization and emergency descents to the forefront. So what happens when the airplane loses cabin pressure, and what is a pilot to do?
Rapid and explosive decompression are serious concerns. This is when the cabin loses pressure at an alarming rate and can have serious repercussions.
A hole in the tail of a Southwest Airlines 737
These emergencies are real attention getters. Pilots will physically feel a “kick in the chest” as their lungs adjust to the change in pressure. Cabin temperature will instantly drop well below freezing while moisture in the air condenses to form a thick fog within the airplane. Amid these distractions, the pilot’s number one priority is to retain consciousness by donning an oxygen mask, then to initiate an emergency descent.
Complete structural failure of a 737-200 in Hawaii.
Not knowing the cause of depressurization, it’s a good idea to assume the worst: structural failure. It may be tempting to dive down at maximum speed, but any increase in airspeed will increase stress on the airframe. Say you are flying at 300 knots when the event occurs. Since the airframe hasn’t completely ripped apart at 300 knots, you must be “safe” at that speed. Consider that to be your new never-exceed speed. Chop the power, extend flight spoilers (if you have them), and pitch down to maintain no greater than 300 knots.
For those of us working as professional pilots in pressurized aircraft, the decisions are black and white. Commercial operators train their pilots in procedures for cabin depressurization. From a pilot’s perspective, it is as simple as following a mental checklist, backed up by the appropriate emergency checklist at a later time.
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