Narrative:

The situation began as we were descending through FL280. Our clearance was for pilot's discretion down to FL240 and we were navigating direct to fingr intersection on the fingr 2 arrival into ads. Passing through FL280, the 'door' light came on on the annunciator panel, indicating that the door was no longer fully closed. At that time the cabin pressure decreased at a very high rate. The other crew member and I then donned our oxygen masks and began an emergency descent procedure. I was the PNF and therefore it was my responsibility for radio communications. The center frequency was very congested at the time which caused a delay in my being able to request a lower altitude. I was finally able to advise ATC that we need a lower altitude immediately, at which time they cleared us down to 12000 ft. However, by the time we received that clearance, we were already passing through approximately FL225 which was 1500 ft below our last assigned altitude. Once we got down to an altitude where oxygen was no longer needed, we continued on to our destination airport without further incidence. This chain of events happened very quickly. To have prevented the altitude excursion, a couple of things might have been done. First, we probably could have leveled off at FL240 and waited to receive a lower altitude assignment. Our oxygen was working properly which would've allowed us to stay there for a few moments. However, we were initially concerned about the integrity of the door and therefore wanted to land as soon as possible at that point in time. The other action we might have taken was to squawk 7700 in order to alert the ATC controller to our situation. Callback conversation with reporter revealed the following information: the reporter was the first officer PNF. He said that the door had been closed from the inside and the crew had complied with company procedures for closing and locking the door. This entails moving a safety bolt which is a bar that is slid across the door handle. The inside locking mechanism is the prime lock for the door. The cargo net was also engaged on the door. Both of these steps are to preclude the loss of the outwardopening door in the event of an inadvertent unseating of the door. That is just what happened. This door is an 'after market conversion.' when the door did become unseated the aircraft lost cabin pressure quite rapidly. During the postflt inspection it was found that the locking handle was out of adjustment. The external handle is supposed to fit flush with the door when it is closed and locked. The mechanic took only 5 mins to 'adjust' the handle so that the handle on the outside did close flush with the door. Reporter suggested that the only way to determine proper closure is for the crew to check this on their preflight, having one crew member close it from the inside and the other observe the exterior latch mechanism's position relative to the door. The flight was an atx service. The captain filed a company report but the crew has had no 'feedback' from management. Supplemental information from acn 411835: due to radio congestion and my rapid descent we passed through FL240 just prior to receiving a clearance for lower. (ZFW continued to approve lower altitudes and issue vectors. They made no reference to traffic conflicts nor did I hear them move another aircraft for us.) when this occurred we were flying in VMC and we were able to maintain VMC. After we realized by visual and audible inspection that the door was latched and secured we continued to ads at lower altitude. Upon landing the mechanics found that the spring in the door release handle had broken allowing the weight of the handle to activate the door microswitch. When this switch is activated it also dumps cabin pressure. I believe we handled this situation well with the exception of declaring an emergency. I think ATC might have been able to approve lower faster had we declared an emergency. Callback conversation with reporter revealed the following information: reporter stated that he learned after landing that the door latch handle spring broke causing the handle to activate the cockpit door open light. When activating the light the aircraft pressurization will automatically dump in order to prevent possible opening of thedoor and its loss. The door was still fully latched shut and the flight crew did not hear any air noise escaping from the door or light in the seal area around the door. The aircraft, a dassault falcon 20, is an old aircraft built in the late 1960's, and previously used by a large air cargo company. The door is a more recently designed cargo, which was specifically designed to not open in-flight in case of any latching problem as long as the door warning light is out.

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Original NASA ASRS Text

Title: CB, A DSNDING DA20, LOSES ABILITY TO STAY PRESSURIZED WHEN THE CABIN DOOR LIGHT INDICATES A DOOR THAT HAS BECOME 'UNSEATED' IN THE FRAME. ACFT LEAVES FL240 BEFORE AMENDED CLRNC IS RECEIVED FROM ATC.

Narrative: THE SIT BEGAN AS WE WERE DSNDING THROUGH FL280. OUR CLRNC WAS FOR PLT'S DISCRETION DOWN TO FL240 AND WE WERE NAVING DIRECT TO FINGR INTXN ON THE FINGR 2 ARR INTO ADS. PASSING THROUGH FL280, THE 'DOOR' LIGHT CAME ON ON THE ANNUNCIATOR PANEL, INDICATING THAT THE DOOR WAS NO LONGER FULLY CLOSED. AT THAT TIME THE CABIN PRESSURE DECREASED AT A VERY HIGH RATE. THE OTHER CREW MEMBER AND I THEN DONNED OUR OXYGEN MASKS AND BEGAN AN EMER DSCNT PROC. I WAS THE PNF AND THEREFORE IT WAS MY RESPONSIBILITY FOR RADIO COMS. THE CTR FREQ WAS VERY CONGESTED AT THE TIME WHICH CAUSED A DELAY IN MY BEING ABLE TO REQUEST A LOWER ALT. I WAS FINALLY ABLE TO ADVISE ATC THAT WE NEED A LOWER ALT IMMEDIATELY, AT WHICH TIME THEY CLRED US DOWN TO 12000 FT. HOWEVER, BY THE TIME WE RECEIVED THAT CLRNC, WE WERE ALREADY PASSING THROUGH APPROX FL225 WHICH WAS 1500 FT BELOW OUR LAST ASSIGNED ALT. ONCE WE GOT DOWN TO AN ALT WHERE OXYGEN WAS NO LONGER NEEDED, WE CONTINUED ON TO OUR DEST ARPT WITHOUT FURTHER INCIDENCE. THIS CHAIN OF EVENTS HAPPENED VERY QUICKLY. TO HAVE PREVENTED THE ALT EXCURSION, A COUPLE OF THINGS MIGHT HAVE BEEN DONE. FIRST, WE PROBABLY COULD HAVE LEVELED OFF AT FL240 AND WAITED TO RECEIVE A LOWER ALT ASSIGNMENT. OUR OXYGEN WAS WORKING PROPERLY WHICH WOULD'VE ALLOWED US TO STAY THERE FOR A FEW MOMENTS. HOWEVER, WE WERE INITIALLY CONCERNED ABOUT THE INTEGRITY OF THE DOOR AND THEREFORE WANTED TO LAND ASAP AT THAT POINT IN TIME. THE OTHER ACTION WE MIGHT HAVE TAKEN WAS TO SQUAWK 7700 IN ORDER TO ALERT THE ATC CTLR TO OUR SIT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE FO PNF. HE SAID THAT THE DOOR HAD BEEN CLOSED FROM THE INSIDE AND THE CREW HAD COMPLIED WITH COMPANY PROCS FOR CLOSING AND LOCKING THE DOOR. THIS ENTAILS MOVING A SAFETY BOLT WHICH IS A BAR THAT IS SLID ACROSS THE DOOR HANDLE. THE INSIDE LOCKING MECHANISM IS THE PRIME LOCK FOR THE DOOR. THE CARGO NET WAS ALSO ENGAGED ON THE DOOR. BOTH OF THESE STEPS ARE TO PRECLUDE THE LOSS OF THE OUTWARDOPENING DOOR IN THE EVENT OF AN INADVERTENT UNSEATING OF THE DOOR. THAT IS JUST WHAT HAPPENED. THIS DOOR IS AN 'AFTER MARKET CONVERSION.' WHEN THE DOOR DID BECOME UNSEATED THE ACFT LOST CABIN PRESSURE QUITE RAPIDLY. DURING THE POSTFLT INSPECTION IT WAS FOUND THAT THE LOCKING HANDLE WAS OUT OF ADJUSTMENT. THE EXTERNAL HANDLE IS SUPPOSED TO FIT FLUSH WITH THE DOOR WHEN IT IS CLOSED AND LOCKED. THE MECH TOOK ONLY 5 MINS TO 'ADJUST' THE HANDLE SO THAT THE HANDLE ON THE OUTSIDE DID CLOSE FLUSH WITH THE DOOR. RPTR SUGGESTED THAT THE ONLY WAY TO DETERMINE PROPER CLOSURE IS FOR THE CREW TO CHK THIS ON THEIR PREFLT, HAVING ONE CREW MEMBER CLOSE IT FROM THE INSIDE AND THE OTHER OBSERVE THE EXTERIOR LATCH MECHANISM'S POS RELATIVE TO THE DOOR. THE FLT WAS AN ATX SVC. THE CAPT FILED A COMPANY RPT BUT THE CREW HAS HAD NO 'FEEDBACK' FROM MGMNT. SUPPLEMENTAL INFO FROM ACN 411835: DUE TO RADIO CONGESTION AND MY RAPID DSCNT WE PASSED THROUGH FL240 JUST PRIOR TO RECEIVING A CLRNC FOR LOWER. (ZFW CONTINUED TO APPROVE LOWER ALTS AND ISSUE VECTORS. THEY MADE NO REF TO TFC CONFLICTS NOR DID I HEAR THEM MOVE ANOTHER ACFT FOR US.) WHEN THIS OCCURRED WE WERE FLYING IN VMC AND WE WERE ABLE TO MAINTAIN VMC. AFTER WE REALIZED BY VISUAL AND AUDIBLE INSPECTION THAT THE DOOR WAS LATCHED AND SECURED WE CONTINUED TO ADS AT LOWER ALT. UPON LNDG THE MECHS FOUND THAT THE SPRING IN THE DOOR RELEASE HANDLE HAD BROKEN ALLOWING THE WT OF THE HANDLE TO ACTIVATE THE DOOR MICROSWITCH. WHEN THIS SWITCH IS ACTIVATED IT ALSO DUMPS CABIN PRESSURE. I BELIEVE WE HANDLED THIS SIT WELL WITH THE EXCEPTION OF DECLARING AN EMER. I THINK ATC MIGHT HAVE BEEN ABLE TO APPROVE LOWER FASTER HAD WE DECLARED AN EMER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE LEARNED AFTER LNDG THAT THE DOOR LATCH HANDLE SPRING BROKE CAUSING THE HANDLE TO ACTIVATE THE COCKPIT DOOR OPEN LIGHT. WHEN ACTIVATING THE LIGHT THE ACFT PRESSURIZATION WILL AUTOMATICALLY DUMP IN ORDER TO PREVENT POSSIBLE OPENING OF THEDOOR AND ITS LOSS. THE DOOR WAS STILL FULLY LATCHED SHUT AND THE FLC DID NOT HEAR ANY AIR NOISE ESCAPING FROM THE DOOR OR LIGHT IN THE SEAL AREA AROUND THE DOOR. THE ACFT, A DASSAULT FALCON 20, IS AN OLD ACFT BUILT IN THE LATE 1960'S, AND PREVIOUSLY USED BY A LARGE AIR CARGO COMPANY. THE DOOR IS A MORE RECENTLY DESIGNED CARGO, WHICH WAS SPECIFICALLY DESIGNED TO NOT OPEN INFLT IN CASE OF ANY LATCHING PROB AS LONG AS THE DOOR WARNING LIGHT IS OUT.

Data retrieved from NASA's ASRS site as of July 2007 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.