Socata (Aerospatiale); Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 53.3; Flight Crew Total 1134; Flight Crew Type 410
Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Other / Unknown
Air Traffic Control Issued New Clearance; Aircraft Equipment Problem Dissipated; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Weather
Flying at 31;000 ft. and the pressurization audible alarm sounded; and we noticed that the cabin pressure was climbing.  It was at 9;800 ft. normally; but had risen to 12;500 ft.  I donned my oxygen mask as the cabin pressure over the next 1-2 minutes rose to a maximum of 15;500 ft.  At 15;000 ft. we began an emergency descent.  As we were setting up for the descent the emergency descent mode (EDM) on the plane took over and began turning the plane 90 degrees from its present course; I deactivated the EMD and corrected the heading back to a safe heading (bad weather was all around us).  I then notified ATC that we would need to begin an emergency descent due to pressure loss in the cabin.I requested 15;000 ft. altitude; and was cleared to descend (while I was already descending).  Once we reached 15;000 ft. the pressurization system began to catch up and the cabin pressure had stabilized at 7;200 ft. MSL.  We flew the remainder of the flight at 15;000 ft. and monitored the cabin pressure.  We landed without incident.  The 3 passengers reported to me to be fine.  The passenger oxygen masks were deployed when the plane began the EDM.Once on the ground i contacted the FBO to determine maintenance and repair requirements.  The problem had occurred before in very rare identical situation.  Rain/ice conditions.  Apparently; a slight amount of moisture in the door seal forms ice; and the seal breaks allowing for pressure from the inside to leak out.  Once we reached a lower altitude the pressure reached normal; and the remainder of the flight was uneventful.After discussions with the FBO I was able to clean the seals and on the flight out; we monitored the cabin differential pressure closely up through 12;500 ft.  Our plan was to return home at 12;500 ft. if there was any indication of an issue; but the cabin differential remained at 6.0 psi the entire flight.  We have added to the preflight checklist; to wipe down door seals prior to each flight.
Pilot flying TBM 940 aircraft reported cabin pressurization problem in cruise. Descent was initiated to lower altitude and cabin pressure stabilized.