PLT OF CPR SMT ACFT MADE A RAPID DSCNT AFTER LOSING ACFT CABIN PRESSURIZATION AT HIGH ALT.

Narrative

ON MAR/TUE/93 AT ABOUT XX30 OVER SBJ VOR AT FL260 CABIN DOOR SEAL DEFLATED CAUSING RAPID DEPRESSURIZATION OF CABIN. I DONNED MY OXYGEN MASK; ADVISED CTR OF PROB; INITIATED A FAIRLY RAPID DSCNT TO LOWER ALT. AT THE SAME TIME; I CHKED TO BE SURE THE 5 PAX WERE USING WERE USING THEIR MASKS; AND TURNED OFF J75 AIRWAY TO THE R 35 DEGS AND ADVISED ZNY I WAS DSNDING. CTLR TOLD ME TO MAINTAIN FL240. I SAID I WAS UNABLE AND REQUESTED 15000 FT. AFTER A MIN THE CTR CTLR CLRED ME TO 15000 AND BACK ON COURSE. SHORTLY THEREAFTER; I WAS TURNED OVER TO NY APCH; WHO WORKED ME DOWN TO A LOWER ALT AT WHICH I CANCELLED IFR AND CONTINUED TO MY DEST OF MTN. THE DOOR SEAL LATER RE- INFLATED. SUSPECT ICE IN DOOR SEAL LINE HAD FROZEN WHERE IT GOES THROUGH THE L WHEEL WELL AREA. AN 'M AND D' FORM HAS BEEN SENT TO THE LCL FSDO IN REF TO THIS PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE THOUGHT THAT HE HAD SAID ENOUGH TO THE CTLR THAT ATC WOULD KNOW THAT HE COULD NOT STAY AT HIGH ALT ANY LONGER. HOWEVER; ATC DID NOT REACT AT FIRST TO AN EMER UNTIL A MOMENT LATER WHEN THE CTLR CONCLUDED THAT THE ACFT WAS GOING DOWN NO MATTER WHAT! SUBSEQUENT INVESTIGATION REVEALED THAT THE CABIN DOOR PRESSURIZATION SEAL DOES FREEZE SINCE IT IS NOT PROTECTED AND THEREFORE; IS SUBJECT TO CAUSING A LOSS OF CABIN PRESSURE. FAA FSDO PERSONNEL ALSO ADVISED HIM TO STATE 'EMER' THE NEXT TIME.