Depressurization

Structural failure with hull breach results in rapid loss of cabin pressure—a disorienting event that may include fogging, immediate loss of air in the lungs, possible ear pain, and at higher altitudes, leaves only a few seconds of useful consciousness. But most times, the loss of pressure is more insidious where the first clue of a problem is the cockpit warning.

Reaction is mostly the same regardless of how it happens, and it can be rehearsed. Warnings include:

 

  1. Just a cabin altitude warning light (CAW)
  2. A CAW and intermittent horn
  3. An intermittent horn
  4. Hissing sound
  5. Rapidly climbing cabin indication on the pressurization system.

 

The beauty is that pilots can be faced with seeing/experiencing any number of warnings and responding appropriately. For example, if they’re below 10,000′ and notice the cabin climb rate is high, they can do the correct reactions for that situation, which may not require anything to dramatic. But the action must be done in the right order and rate–turn on both engine bleeds right away and the cabin will descend dramatically. The simulator will display “[feel ear popping]” which will trigger looking at the pressurization panel to notice that only the left pack was running on the APU. How should this be corrected? That’s what the simulation will provide—practice. A Quick Reference Handbook page can be presented in response to selecting a persistent QRH button.