Citation II S2/Bravo (C550)
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 100; Flight Crew Total 3200; Flight Crew Type 850
Aircraft Equipment Problem Critical
General Declared Emergency; General Maintenance Action
Aircraft
Our aircraft experienced a rapid decompression while descending from FL300 to 12;000. The decompression occurred around FL280. We recognized the situation and initiated an emergency descent to 10;000. Upon reaching a safe altitude of 12;000 FT we advised ATC of the decompression; and declared an emergency. At this time ATC cleared us to descend to 2;800 and proceed to an IAF at our destination. The crew did so and landed safely.The rapid decompression was thought to have been caused by a build up of moisture in the door seal which turned to ice crystals at altitude. This blocked the airflow into the door seal causing a leak that allowed the cabin to rapidly depressurize. This was corrected by draining the door seal and lines to it more frequently during maintenance checks.
A CE550 flight crew experienced a rapid decompression as they began descent to their destination. They declared an emergency and were expedited to a safe landing by ATC.