Narrative:

I am a captain for a regional airline and fly a 19 passenger aircraft with no F/a. On the flight in question 1 of the smaller cowling panels on the right-hand engine separated from the aircraft shortly after takeoff. Prior to this flight's scheduled departure, maintenance had been performing some work on the right-hand engine. After they had completed their work, the first officer did another walk-around, observing that all the cowling panels which had been removed had been securely fastened. As he was doing this, one mechanic was doing what is always the last item after recowling an engine--wiping off oily fingerprints from the cowling. At this time he was standing in front of the panel in question, which would have prevented the first officer from viewing the lower portion of it. This particular panel, by the way, had not even been removed. We discovered later that the lower 8 of the 21 total quarter-turns had been loosened to provide only limited access behind that panel. (This small portion with the relative wind's force was enough to rip all the remaining quarter-turns through their respective holes in the panel and allow its sep from the aircraft.) when the first officer returned to the cockpit, it was verified that everything looked secure, and we completed the before start checks. The passenger boarded, we taxied out and executed a normal takeoff on 18L. As we were initiating our departure turn at 400' and changing over to departure control, a passenger stepped forward and informed me that part of the right-hand engine cowling had separated from the aircraft. After visually confirming this, I informed departure control that we needed to return for landing. We landed uneventfully on 18L, returned to the ramp and deplaned our 13 passenger. After exiting the aircraft and inspecting the engine, we found all but 7 of the quarter-turns still in their secure, locked position. Nothing at all was damaged except for the cowling panel itself, which was found on the airport property about 1/2 hour later. A primary factor which makes the professional aviation environment so safe is the redundancy in human scrutiny. It's not that one colleague distrusts another when a pilot double-checks something when a mechanic has already done the same thing, it's a mutual understanding that as humans, all of us are capable of making mistakes, and we welcome and expect the scrutiny of others to weed out inevitable mistakes. This is the only way we create the near perfect performance which we have come to expect in this industry. The event documented in this report demonstrates that even with conscientious professional involved, an incident like this can still occur. All it takes is an unusual combination of events to create just a small gap in this system of double scrutiny. This is why we can never be too careful. Supplemental information from acn 160437: after the maintenance was done and engine ground run I helped replace the lower cowling and then replaced the outboard aft cowling. I never checked the inboard SID cowling (which was loosened before I got to the aircraft). The whole incident was an oversight by the supervisor, mechanic, flight crew and myself.

Related reports:

Google
 

Original NASA ASRS Text

Title: UNSECURED ENGINE PANEL DEPARTS ACFT SHORTLY AFTER TKOF FROM DFW.

Narrative: I AM A CAPT FOR A REGIONAL AIRLINE AND FLY A 19 PAX ACFT WITH NO F/A. ON THE FLT IN QUESTION 1 OF THE SMALLER COWLING PANELS ON THE RIGHT-HAND ENG SEPARATED FROM THE ACFT SHORTLY AFTER TKOF. PRIOR TO THIS FLT'S SCHEDULED DEP, MAINT HAD BEEN PERFORMING SOME WORK ON THE RIGHT-HAND ENG. AFTER THEY HAD COMPLETED THEIR WORK, THE F/O DID ANOTHER WALK-AROUND, OBSERVING THAT ALL THE COWLING PANELS WHICH HAD BEEN REMOVED HAD BEEN SECURELY FASTENED. AS HE WAS DOING THIS, ONE MECH WAS DOING WHAT IS ALWAYS THE LAST ITEM AFTER RECOWLING AN ENG--WIPING OFF OILY FINGERPRINTS FROM THE COWLING. AT THIS TIME HE WAS STANDING IN FRONT OF THE PANEL IN QUESTION, WHICH WOULD HAVE PREVENTED THE F/O FROM VIEWING THE LOWER PORTION OF IT. THIS PARTICULAR PANEL, BY THE WAY, HAD NOT EVEN BEEN REMOVED. WE DISCOVERED LATER THAT THE LOWER 8 OF THE 21 TOTAL QUARTER-TURNS HAD BEEN LOOSENED TO PROVIDE ONLY LIMITED ACCESS BEHIND THAT PANEL. (THIS SMALL PORTION WITH THE RELATIVE WIND'S FORCE WAS ENOUGH TO RIP ALL THE REMAINING QUARTER-TURNS THROUGH THEIR RESPECTIVE HOLES IN THE PANEL AND ALLOW ITS SEP FROM THE ACFT.) WHEN THE F/O RETURNED TO THE COCKPIT, IT WAS VERIFIED THAT EVERYTHING LOOKED SECURE, AND WE COMPLETED THE BEFORE START CHKS. THE PAX BOARDED, WE TAXIED OUT AND EXECUTED A NORMAL TKOF ON 18L. AS WE WERE INITIATING OUR DEP TURN AT 400' AND CHANGING OVER TO DEP CTL, A PAX STEPPED FORWARD AND INFORMED ME THAT PART OF THE RIGHT-HAND ENG COWLING HAD SEPARATED FROM THE ACFT. AFTER VISUALLY CONFIRMING THIS, I INFORMED DEP CTL THAT WE NEEDED TO RETURN FOR LNDG. WE LANDED UNEVENTFULLY ON 18L, RETURNED TO THE RAMP AND DEPLANED OUR 13 PAX. AFTER EXITING THE ACFT AND INSPECTING THE ENG, WE FOUND ALL BUT 7 OF THE QUARTER-TURNS STILL IN THEIR SECURE, LOCKED POS. NOTHING AT ALL WAS DAMAGED EXCEPT FOR THE COWLING PANEL ITSELF, WHICH WAS FOUND ON THE ARPT PROPERTY ABOUT 1/2 HR LATER. A PRIMARY FACTOR WHICH MAKES THE PROFESSIONAL AVIATION ENVIRONMENT SO SAFE IS THE REDUNDANCY IN HUMAN SCRUTINY. IT'S NOT THAT ONE COLLEAGUE DISTRUSTS ANOTHER WHEN A PLT DOUBLE-CHKS SOMETHING WHEN A MECH HAS ALREADY DONE THE SAME THING, IT'S A MUTUAL UNDERSTANDING THAT AS HUMANS, ALL OF US ARE CAPABLE OF MAKING MISTAKES, AND WE WELCOME AND EXPECT THE SCRUTINY OF OTHERS TO WEED OUT INEVITABLE MISTAKES. THIS IS THE ONLY WAY WE CREATE THE NEAR PERFECT PERFORMANCE WHICH WE HAVE COME TO EXPECT IN THIS INDUSTRY. THE EVENT DOCUMENTED IN THIS RPT DEMONSTRATES THAT EVEN WITH CONSCIENTIOUS PROFESSIONAL INVOLVED, AN INCIDENT LIKE THIS CAN STILL OCCUR. ALL IT TAKES IS AN UNUSUAL COMBINATION OF EVENTS TO CREATE JUST A SMALL GAP IN THIS SYS OF DOUBLE SCRUTINY. THIS IS WHY WE CAN NEVER BE TOO CAREFUL. SUPPLEMENTAL INFO FROM ACN 160437: AFTER THE MAINT WAS DONE AND ENG GND RUN I HELPED REPLACE THE LOWER COWLING AND THEN REPLACED THE OUTBOARD AFT COWLING. I NEVER CHKED THE INBOARD SID COWLING (WHICH WAS LOOSENED BEFORE I GOT TO THE ACFT). THE WHOLE INCIDENT WAS AN OVERSIGHT BY THE SUPVR, MECH, FLT CREW AND MYSELF.

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.