2010-06 · NASA ASRS report 894209
A C-560 rapidly depressurized at FL340. The cabin altitude exceeded 25;000 FT during the emergency descent. There were no injuries and the aircraft was diverted to a nearby airport for a normal approach and landing.
While en route at FL340 we heard a loud high pitched whistle which seemed to originate form the main cabin door. We then noticed the cabin rate climbing in excess of 6;000 FPM and a steady rapid climb in the cabin altitude form normal indications. Upon noticing the increasing cabin rate the pilot not flying donned his oxygen mask and an immediate descent was requested and approved by the controlling ATC facility. Approximately 30 seconds to 1 minute the 'Cabin Alt 10;000 FT' red annunciator illuminated triggering the Master Warning causing the passenger oxygen masks to drop. Once the red Master Warning was illuminated we issued a positive exchange of flight controls while descending and I (pilot flying) donned my oxygen mask. After another positive exchange of flight controls were completed and the pilot flying was at the controls; the pilot not flying communicated to ATC that we were conducting an emergency descent due to a loss of pressurization and a quick check to ensure the safety of the passengers was done to ensure they were utilizing their oxygen mask. We then referred to appropriate checklist to confirm everything was covered accordingly. During this time a cabin altitude of 25;000 FT was noticed by the pilot flying while in the descent. ATC then issued an altitude of 15;000 FT. We requested an altitude of 10;000 FT so that we could come off oxygen and communicate clearly both as a crew and to check with the passengers to ensure everyone was OK. This altitude of 10;000 FT was approved. A continuous descent was made down to our 10;000 FT cleared altitude. Once the red Master Warning had extinguished we came off oxygen and notified ATC that we would have to divert. After being cleared to a nearby airport via a heading and given a descent to 5;000 ft ATC then asked if we required any assistance; which we refused. A normal approach and landing was made on the Runway. Dispatch and Maintenance Control was then notified. A van service was arranged by Dispatch to get our passengers to their planned destination. There was some confusion between the crew as to whether or not an actual emergency was declared. Crew communication during the incident was done primarily with hand signals and pointing due to the inability to communicate effectively while on oxygen. Whether an actual emergency was declared or not we seemed to be granted priority handling by ATC. Our every request was granted.
In cruise flight at FL340 there was a loud whistling sound. Twice earlier there had been a faint whistling sound that was found to be the cooler drawer. This time the sound was louder and when I looked at the drawer it was closed. While turned around [I noticed] the sound seemed to be coming from the door area. I turned back to the front and checked that the door had not come unlocked. When I saw that there was no light indicating that it had and I could feel my ears start to fill (pressure). I then looked at the cabin pressure rate and saw the indicator needle around positive six.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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