Narrative:

We were in level cruise on a 2 hour flight at 39000 ft when we experienced a noise similar to a rifle shot and the airplane started to depressurize. Making a very quick determination that we had a broken cockpit side window, I was not sure that we did not also have an explosive decompression pending. While this was not as explosive decompression, I could not take any chances, so I started the emergency descent procedure as taught in our simulator training. During the descent from 39000 ft to 12000 ft, my co-pilot was trying to establish 2-WAY communications with ATC. Before this incident, we were using our headsets for communication. With the headset off, the oxygen mask was not allowing him to receive communication, only transmit. This caused some confusion, during which time he picked up the hand microphone and made 2 or more blind xmissions announcing what our problem was and what we were doing. Later in our descent he did reestablish 2-WAY communication. After we reached 12000 ft, the next ATC controller asked us what our intentions were. Since we had about 1.0-1.5 psi on the pressurization and thought the window that was still intact was going to be fine at that low psi, I said that we wanted to continue on to our destination. ATC also asked if we were declaring an emergency or needed any equipment. I told the copilot that we did not need to declare an emergency at that point. It seemed odd to me that they were asking this question, since I took it for granted that by squawking 7700 when we started our descent that we were already on emergency status. A pressurization problem at 12000 ft wouldn't normally require declaring an emergency. Our emergency was over at that point. Upon landing at our destination, we arranged for a ferry permit from the flight standards inspector, and flew the airplane to a maintenance center to have the window replaced. It was then determined that the window had been installed incorrectly in may/xx/93 and one of the bolts securing the window had chafed the window until it was weakened and suddenly split. With over 16 yrs of corporate flying in mostly turboprops and jets, this was my first time to declare an emergency. Never having had a high altitude pressurization problem, my only experience for handling and emergency of this magnitude has been simulator practice. It has always been emphasized that the type of failure at high altitude requires immediate attention, due to the very short time of useful consciousness if there is a complete loss of pressurization. In hindsight, I do believe that if we had been IMC, that I would have been motivated to talk to ATC about our need for an emergency descent. That observation is easier to make sitting at a desk, and not at 39000 ft with a sudden broken window. Supplemental information from acn 295886: in the process of putting on my mask my sunglasses were knocked off and my headset kept getting in the way so I couldn't get the mask to properly seal to my face. I wanted to communication our situation to ATC as soon as possible but because my headset was not on properly on nor were the radio switches in the correct position, I wasn't able to have effective communication with ATC until we had descended several thousand feet. I did make 2 or 3 xmissions 'in the blind' but heard no reply as the radio switches were out of position.

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Original NASA ASRS Text

Title: LOSS OF PRESSURIZATION - DSCNT PROC EMER.

Narrative: WE WERE IN LEVEL CRUISE ON A 2 HR FLT AT 39000 FT WHEN WE EXPERIENCED A NOISE SIMILAR TO A RIFLE SHOT AND THE AIRPLANE STARTED TO DEPRESSURIZE. MAKING A VERY QUICK DETERMINATION THAT WE HAD A BROKEN COCKPIT SIDE WINDOW, I WAS NOT SURE THAT WE DID NOT ALSO HAVE AN EXPLOSIVE DECOMPRESSION PENDING. WHILE THIS WAS NOT AS EXPLOSIVE DECOMPRESSION, I COULD NOT TAKE ANY CHANCES, SO I STARTED THE EMER DSCNT PROC AS TAUGHT IN OUR SIMULATOR TRAINING. DURING THE DSCNT FROM 39000 FT TO 12000 FT, MY CO-PLT WAS TRYING TO ESTABLISH 2-WAY COMS WITH ATC. BEFORE THIS INCIDENT, WE WERE USING OUR HEADSETS FOR COM. WITH THE HEADSET OFF, THE OXYGEN MASK WAS NOT ALLOWING HIM TO RECEIVE COM, ONLY XMIT. THIS CAUSED SOME CONFUSION, DURING WHICH TIME HE PICKED UP THE HAND MIKE AND MADE 2 OR MORE BLIND XMISSIONS ANNOUNCING WHAT OUR PROB WAS AND WHAT WE WERE DOING. LATER IN OUR DSCNT HE DID REESTABLISH 2-WAY COM. AFTER WE REACHED 12000 FT, THE NEXT ATC CTLR ASKED US WHAT OUR INTENTIONS WERE. SINCE WE HAD ABOUT 1.0-1.5 PSI ON THE PRESSURIZATION AND THOUGHT THE WINDOW THAT WAS STILL INTACT WAS GOING TO BE FINE AT THAT LOW PSI, I SAID THAT WE WANTED TO CONTINUE ON TO OUR DEST. ATC ALSO ASKED IF WE WERE DECLARING AN EMER OR NEEDED ANY EQUIP. I TOLD THE COPLT THAT WE DID NOT NEED TO DECLARE AN EMER AT THAT POINT. IT SEEMED ODD TO ME THAT THEY WERE ASKING THIS QUESTION, SINCE I TOOK IT FOR GRANTED THAT BY SQUAWKING 7700 WHEN WE STARTED OUR DSCNT THAT WE WERE ALREADY ON EMER STATUS. A PRESSURIZATION PROB AT 12000 FT WOULDN'T NORMALLY REQUIRE DECLARING AN EMER. OUR EMER WAS OVER AT THAT POINT. UPON LNDG AT OUR DEST, WE ARRANGED FOR A FERRY PERMIT FROM THE FLT STANDARDS INSPECTOR, AND FLEW THE AIRPLANE TO A MAINT CTR TO HAVE THE WINDOW REPLACED. IT WAS THEN DETERMINED THAT THE WINDOW HAD BEEN INSTALLED INCORRECTLY IN MAY/XX/93 AND ONE OF THE BOLTS SECURING THE WINDOW HAD CHAFED THE WINDOW UNTIL IT WAS WEAKENED AND SUDDENLY SPLIT. WITH OVER 16 YRS OF CORPORATE FLYING IN MOSTLY TURBOPROPS AND JETS, THIS WAS MY FIRST TIME TO DECLARE AN EMER. NEVER HAVING HAD A HIGH ALT PRESSURIZATION PROB, MY ONLY EXPERIENCE FOR HANDLING AND EMER OF THIS MAGNITUDE HAS BEEN SIMULATOR PRACTICE. IT HAS ALWAYS BEEN EMPHASIZED THAT THE TYPE OF FAILURE AT HIGH ALT REQUIRES IMMEDIATE ATTN, DUE TO THE VERY SHORT TIME OF USEFUL CONSCIOUSNESS IF THERE IS A COMPLETE LOSS OF PRESSURIZATION. IN HINDSIGHT, I DO BELIEVE THAT IF WE HAD BEEN IMC, THAT I WOULD HAVE BEEN MOTIVATED TO TALK TO ATC ABOUT OUR NEED FOR AN EMER DSCNT. THAT OBSERVATION IS EASIER TO MAKE SITTING AT A DESK, AND NOT AT 39000 FT WITH A SUDDEN BROKEN WINDOW. SUPPLEMENTAL INFO FROM ACN 295886: IN THE PROCESS OF PUTTING ON MY MASK MY SUNGLASSES WERE KNOCKED OFF AND MY HEADSET KEPT GETTING IN THE WAY SO I COULDN'T GET THE MASK TO PROPERLY SEAL TO MY FACE. I WANTED TO COM OUR SIT TO ATC AS SOON AS POSSIBLE BUT BECAUSE MY HEADSET WAS NOT ON PROPERLY ON NOR WERE THE RADIO SWITCHES IN THE CORRECT POS, I WASN'T ABLE TO HAVE EFFECTIVE COM WITH ATC UNTIL WE HAD DSNDED SEVERAL THOUSAND FEET. I DID MAKE 2 OR 3 XMISSIONS 'IN THE BLIND' BUT HEARD NO REPLY AS THE RADIO SWITCHES WERE OUT OF POS.

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.