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Old 5th August 2011 | 11:04
  #26 (permalink)  
Swedish Steve
 
Joined: Apr 2005
Posts: 569
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From: Stockholm Sweden
You can get in this situation only if you descent in a very high rate for a longer time.
In this case the aircraft altitude can pass the cabin altitude.
A couple of years ago I was called out to a B757.
During the descent into a sea level airport, at about 8000ft the crew had heard a bang, felt pressure in their ears, looked up and saw the cabin was at the same altitude as the aircraft and followed it down to the ground.
They thought that the bang had been a failure, and they had a hole in the fuselage. After much inspecting and checking and finding nothing, I decided to pressurise the aircraft. Looking up at the pressure control panel the cabin rate of descent knob was set at min! The aircraft had overtaken the cabin in the descent, the bang was the safety valves opening.
Rate knob reset to the pip, and aircraft departed.
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