Narrative:

We were approaching the VOR [and] had just been cleared to begin our initial descent to FL370 from our cruise altitude of FL410. We had completed the descent checklist; and as we were descending through FL400; we noted the cabin rate-of-climb indicator 'spiking' to a maximum rate-of-climb (6000+ fpm). We had red cabin altitude and master warning lights illuminating and initiated the cabin decompression and the emergency descent checklists. I ensured that the passenger oxygen masks were deployed and instructed our two passengers to don their oxygen masks; advised them that we had a pressurization problem and observed that they in fact had donned their masks and received a 'thumbs up' from them. We observed that the pressurization safety valves had apparently closed because the cabin altitude was limited to approximately 13000 ft. We requested a further descent to the lowest MEA altitude; but were initially restricted to FL290; due to (apparently) active military airspace below us. We clarified that we were declaring an emergency; and were subsequently given a heading for further descent; after a brief delay; down to 12;000 feet MSL. We subsequently confirmed with ATC that our pressurization problem was 'stabilized' as we approached 12;000 ft. On descent. We discussed airport alternatives; and we concluded that a conservative option would be to change our destination to ZZZ; as there would be better support capabilities if required. We had requested ATC to advise our operations command center of our situation and intentions. We briefed several options; and decided on executing the VOR approach and landing. We landed the aircraft without incident or injury and safely taxied to the FBO. We attended to our passengers; who indicated that they were not injured; but were very appreciative and supportive of our efforts. We followed up with operations and management personnel and conducted post-flight activities.

Related reports:

Google
 

Original NASA ASRS Text

Title: A CE-560 Captain reported loss of cabin pressurization at FL400. The Flight Crew declared an emergency; executed an emergency descent; and diverted to the nearest suitable airport.

Narrative: We were approaching the VOR [and] had just been cleared to begin our initial descent to FL370 from our cruise altitude of FL410. We had completed the descent checklist; and as we were descending through FL400; we noted the cabin rate-of-climb indicator 'spiking' to a maximum rate-of-climb (6000+ fpm). We had red cabin altitude and master warning lights illuminating and initiated the cabin decompression and the emergency descent checklists. I ensured that the passenger oxygen masks were deployed and instructed our two passengers to don their oxygen masks; advised them that we had a pressurization problem and observed that they in fact had donned their masks and received a 'thumbs up' from them. We observed that the pressurization safety valves had apparently closed because the cabin altitude was limited to approximately 13000 ft. We requested a further descent to the lowest MEA altitude; but were initially restricted to FL290; due to (apparently) active military airspace below us. We clarified that we were declaring an emergency; and were subsequently given a heading for further descent; after a brief delay; down to 12;000 feet MSL. We subsequently confirmed with ATC that our pressurization problem was 'stabilized' as we approached 12;000 ft. on descent. We discussed airport alternatives; and we concluded that a conservative option would be to change our destination to ZZZ; as there would be better support capabilities if required. We had requested ATC to advise our Operations Command Center of our situation and intentions. We briefed several options; and decided on executing the VOR approach and landing. We landed the aircraft without incident or injury and safely taxied to the FBO. We attended to our passengers; who indicated that they were not injured; but were very appreciative and supportive of our efforts. We followed up with operations and management personnel and conducted post-flight activities.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.