Cabin pressurization is quite a simple but often overlooked system within airliners that is used on the tens of thousands of commercial flights every single day. The only time cabin pressurization is really noticed is when these systems fail. Most recently, this failure was on Alaska Airlines Flight 1282 on January 5th, 2024. But how does cabin pressurization work, and how did it fail on Flight 1282?
With Boeing first implementing a cabin pressurization system on their commercial airliner Model 307 Stratoliner back in the 1930s, such a system is far from novel. The need for a pressurized cabin arose from airliners wanting to fly at a higher altitude to fly faster and above any dangerous weather. This, in turn, means that the people within the cabin need oxygen to breathe at these higher altitudes. Even at 20,000 feet, the cruising altitude of the Model 307 from the 1930s, people would struggle to breathe in the cabin comfortably. Today, airliners fly as high as 40,000 feet, where the atmospheric PSI is only 2.72, miniscule compared to the standard 14.7 PSI at sea level and impossible for passengers to breathe at.
The pressurization system works by using excess air from the airplane’s engine compressors and pumping it into the airtight cabin through a device called the air cabin pressure controller. This process occurs gradually to ensure the passengers barely notice the pressurization. In order to maintain this higher internal pressure within the cabin, the aircraft’s fuselage must be made of strong, light, and airtight materials like aluminum and carbon fiber. The opposite of these materials would be something like a balloon, which expands quite easily when more air is pumped inside to balance the pressure difference between the inside of the balloon and the atmosphere. This concept of excess and outward pressure trying to expand an object is identical to airliners, but the aircraft holds its pressure and shape due to the more rigid materials used. Even with more robust materials, commercials typically simulate an air pressure equivalent to that of around 8,000 feet to prevent putting too much stress on the fuselage.
This pressurization system fails when either the compressor fails, or the fuselage fails. The latter was the case of Flight 1282, when a panel called a “door plug” was blown off the aircraft at 16,000 feet. These door plugs are panels that are inserted into what would be a required emergency exit if the airliner configured their aircraft to have more seats. While investigators are still unsure of the actual cause of this door failure, the most prominent belief is that the bolts securing the door in place were never in place when the plane left Boeing’s factory. The lack of securing bolts compromised a key part of a cabin’s pressurization system, a completely sealed cabin, and resulted in the pressure differences blowing the door off the plane. According to NBC News, Boeing President and CEO Dave Calhoun said, “Whatever final conclusions are reached, Boeing is accountable for what happened… An event like this must not happen on an airplane that leaves our factory.”
Nonetheless, today, without cabin pressurization, the airline industry would be drastically different and most notably less comfortable. The main takeaways from such failures are not fears but rather more attention and safer construction to prevent these incidents in the future.
