FALCON DA20 SUFFERS DECOMPRESSION WHEN THE MODIFIED CARGO DOOR BLOWS OPEN. EMER DSCNT ENSUES WITH REDUCED AIRSPD TO KEEP DOOR FROM BLOWING OFF. RPTR CITES ACFT EQUIP DESIGN PROB.

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WE WERE CLRED TO CROSS NEW HOPE VOR AT 11000 FT. ABOUT 30 MI SW OF EWO VOR THE CABIN ALT STARTED CLBING AS WE WERE DSNDING THROUGH 22000 FT. WE WERE MAINTAINING ABOUT 250 KTS IN THE DSCNT AND A 2000 FPM DSCNT WITH THE AUTOPLT ENGAGED. WHEN THE CABIN ALT STARTED CLBING I TURNED THE AUTOPLT OFF; EXTENDED THE AIR BRAKES AND PULLED THE PWR TO IDLE. THE FO STARTED TRYING TO REGAIN CTL OF THE CABIN. WE ACCELERATED TO AROUND 280-290 KTS AS WE INCREASED OUR RATE OF DSCNT. WE WERE DSNDING AT LEAST 6000 FPM. AT AROUND 18000 FT THE FO NOTICED THAT THE DOOR LIGHT WAS ON AND I TOLD THE JUMPSEATER TO LOCK THE COCKPIT DOOR. I ALSO STARTED SLOWING THE ACFT TO BELOW 250 KTS SO THAT MAYBE THE DOOR WOULD NOT COME ALL THE WAY OPEN. AT AROUND 17000 FT A LOUD BANG WAS HEARD AND THE DOOR CAME OPEN. I ASCERTAINED VERY QUICKLY THAT THE ACFT WAS FLYABLE AND VERIFIED WITH THE FO THAT HE DID INDEED CONNECT THE CARGO STRAP TO THE DOOR BEFORE TKOF. THE FO PUT HIS SHOULDER HARNESS ON AND THEN I GAVE HIM THE ACFT SO I COULD PUT MY SHOULDER HARNESS ON. THE ACFT WANTED TO OSCILLATE BACK AND FORTH AROUND THE VERT AXIS. IT REQUIRED A LOT OF L RUDDER TO PREVENT THE YAWING. AFTER I HAD MY SHOULDER HARNESS ON I TOOK OVER THE FLYING DUTIES AGAIN. WE ASKED FOR PRIORITY HANDLING TO THE SDF ARPT AND APCH HANDED US OVER TO TWR. TWR CLRED US TO LAND RWY 35. WE INSTRUCTED TWR THAT WE WANTED RWY 1 AND THEY CLRED US TO LAND RWY 1. WE RETRACTED THE AIR BRAKES AND SLOWED TO BELOW 200 KTS AND DISCUSSED THE CONFIGN THAT WE WANTED TO LAND THE ACFT IN. WE CAME TO THE CONCLUSION THAT FLAPS 25 DEGS WAS THE BEST CONFIGN AND THAT WE WOULD KEEP IT FAST. WE DID NOT KNOW HOW THE OPEN DOOR WAS AFFECTING THE AIRFLOW OVER THAT WING AND DECIDED THAT WE WOULD LAND AT AROUND 160 KTS. WE EXTENDED THE FLAPS; DLE'S AND GEAR AND LANDED. WE EXITED THE ACFT THROUGH THE DV WINDOW WHEN WE FOUND OUT THE DOOR WOULD NOT OPEN NORMALLY. WE FOUND UPON EXITING THE ACFT THAT THE LADDER WAS OUTSIDE THE ACFT. WE OPENED THE DOOR BY HAND AND FOUND THAT THE ACTUATORS THAT OPEN AND CLOSE THE DOOR WERE BROKEN; THE HINGES THAT HOUSE THE ACTUATORS WERE BENT AND THAT MOST OF THE INTERIOR ON THE DOOR AS WELL AS THE STUFFING HAD BEEN SUCKED OUT. LOOKING BACK ON THE SIT; I LEARNED 4 THINGS. ONE; THAT WE SHOULD HAVE DONNED OUR OXYGEN MASKS. WE DID NOT BECAUSE I FELT THAT WE WOULD NOT BE ABLE TO COMMUNICATE AND THAT WE WOULD BE DOWN IN BREATHABLE AIR IN NO TIME. OUR OXYGEN MASKS DO NOT ALLOW US THE CAPABILITY OF TALKING WITH ONE ANOTHER WITHOUT TAKING THE MASKS OFF. I COULD NOT HAVE COMMUNICATED WITH MY FO AND FLOWN THE ACFT AT THE SAME TIME. WE ARE CORRECTING THIS PROB. EVERY PLT SHOULD MAKE SURE THAT THEY HAVE THE CAPABILITY OF COMMUNICATING WITH THE ENTIRE CREW IN ANY EMER! TWO; I THINK THAT THE NET THAT WAS CONNECTED TO THE DOOR SAVED OUR LIVES. THE COMPANY THAT NOW HOLDS THE SUPPLEMENTAL TYPE CERTIFICATE TO THE DOOR IS BAFFLED AS TO WHY THE DOOR CAME OPEN. WE ARE GOING TO HAVE IT FIXED AND IMPROVED SO THAT THIS WILL NEVER HAPPEN AGAIN. THE ORIGINAL SUPPLEMENTAL TYPE CERTIFICATE DOES NOT HAVE ANY LOCKING PINS TO PREVENT THE LOCKS FROM COMING OPEN. I HOPE ANY DA20 OPERATOR WITH THE ORIGINAL CARGO DOOR HAS THESE PINS INSTALLED. THREE; THE ORIGINAL SUPPLEMENTAL TYPE CERTIFICATE FOR THIS PARTICULAR CARGO CONFIGN HAS A CARGO/BARRIER NET THAT IS NOT CONNECTED TO THE DOOR. THERE IS A NET THAT IS CONNECTED TO A BAR THAT GOES FROM THE CEILING TO THE FLOOR AND IT IS NOT CONNECTED TO THE DOOR. OUR PMI APPROVED A 10G BARRIER NET THAT IS CONNECTED TO THE DOOR. LASTLY; I SHOULD HAVE DECLARED AN EMER INSTEAD OF ASKING FOR PRIORITY HANDLING. THE PRIORITY HANDLING CAME TO MY MIND FIRST AND I INSTRUCTED MY FO TO GET PRIORITY HANDLING. IT WOULD HAVE ENDED THE SAME WAY BUT LOOKING BACK DECLARING AN EMER WOULD HAVE BEEN THE SMARTEST THING TO DO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR WAS REFERRING TO THE MODIFIED CARGO DOOR ON THE DA20. THE REGULAR PAX LOADING DOOR WAS REMOVED AND ENLARGED. IT IS HINGED ON THE TOP. THE DOOR ON THIS ACFT WAS THE DOOR APPROVED WITH THE SUPPLEMENTAL TYPE CERTIFICATE AND DID NOT HAVE THE LOCKING PINS THAT THE RPTR ALLUDES TO IN HIS TEXT. THIS WAS A 1965 MODEL ACFT. THE DOOR WAS MODIFIED USING THE ORIGINAL LOCKING MECHANISMS WHICH LATCHES OVER CTR. THE RPTR FERRIED THE ACFT THE NEXT DAY FOR REPAIRS AND TALKED WITH THE REPAIR ENGINEERS. THEY FELT THAT THE LATCHES HAD BEEN TOO LOOSE; ALLOWING TOO MUCH 'PLAY' AND THUS CAME OPEN. THE MODIFIED NET IN THE SCENARIO KEPT THE DOOR FROM COMING OFF THE ACFT. IF IT HAD; IT IS SAID THAT THE TAIL WOULD HAVE BEEN STRUCK WITH A POSSIBILITY OF DESTROYING THE TAIL COMPLETELY. THE POI OF THE CARRIER HAD APPROVED THE NEWER '10G NET.' THIS WAS THE RPTR'S FIRST EXPERIENCE AND THE CARRIER'S FIRST EXPERIENCE WITH A DOOR COMING OPEN. THEY HAVE 4 ACFT MODIFIED WITH THIS TYPE DOOR; WITHOUT THE LOCKING PINS THAT RPTR RECOMMENDS. THE DOOR IS APPROX 4.5 FT HIGH AND 5 FT WIDE. THE FAA IS SUGGESTING A MODIFICATION TO THE DOOR; BUT NOT ENFORCING THE MODIFICATION. THE MODIFICATION COSTS $600;000 TO PERFORM. THE CARRIER'S POI HAS A COPY OF THIS RPT. THE COM PROB MENTIONED IN THE EVENT OCCURRED BECAUSE THE MIKE IN THE MASK WAS HOOKED UP TO THE ATC XMITTER ONLY. IT HAS BEEN REWORKED SO THAT THE COCKPIT SPEAKER HAS ACCESS TO IT. REGARDING THE DOOR; ANOTHER LARGER CARRIER HAD USED THIS ACFT WITH THE CARGO DOOR AND HAD THEIR OWN DESIGN FOR LOCKING/LATCHING. THEY HAD 4 FAILURES OF THIS DOOR.