Citation V/Ultra/Encore (C560)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 96; Flight Crew Total 4876; Flight Crew Type 600
Communication Breakdown
ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Human Factors
While flying at FL390; I asked to climb to FL410 for light constant turbulence. I was flying with the O2 mask on already; because I fly single-pilot; and upon reaching FL395 I heard a pop and then a small air noise. I knew immediately that my door seal had a leak and I told ATC that I needed [a lower altitude]. I started an emergency descent so that I would not lose the entire cabin. The cabin started to depressurize at approximately 4;000 FPM; so I came down as fast as I could. I was trying to relay to ATC what I needed; but was more concerned with getting the airplane to a safe altitude so that the door seal would stop leaking and repressurize the cabin. ATC asked if I needed to [assistance] and I said yes; so they let me descend to 16;000 ft. After reaching 16;000 ft; the seal stopped leaking and I had a chance to talk to ATC about what happened. We discussed what the problem was and a better way to communicate it to them if this ever happened in the future. This was not our first time our door seal froze in flight so we are currently undergoing extensive maintenance and troubleshooting to find the underlying issue. During the descent; the masks did not drop and none of the passengers were injured or even experienced any real discomfort.
CE-560 pilot reported descending without clearance after he lost cabin pressure when a door seal started leaking.