Narrative:

The left engine cowling came loose and was held on the aircraft by one cam lock. I personally preflted this aircraft, and checked the security of the engine cowling as well as the four lock, unlock alignment marks on the cam lock nuts. The aircraft was landed and brought back to the gate area. Some company mechanics met the aircraft, and a statement was made by one of the mechanics that it was possible for the lock, unlock alignment marks to be in the locked position, and the cowlings seem secure, but the only way to make sure the cowling was secure is to get a wrench and turn the cam lock nuts and feel the detent in the cam lock itself. The company operations manual and procedures prohibit pilots from doing this. I personally feel that there should be more fasteners to hold the cowling in place and a better way to verify the security of the cowling. On landing the partially secure cowling was bumping up against the propeller governor, making the propeller go to the ground, low pitch stop. Causing a big yaw when the power was reduced for landing. Supplemental information from acn 171218. First officer did the preflight and I walked around the aircraft also. The left engine cowling was secure and cam locks were in the locked position, my first officer pushed and pulled on the cowling, it was secure. During climb out a passenger came forward and informed us that left cowling is coming off, when I checked it was hanging on by one lock. We did not declare an emergency, just told ATC that we needed to land immediately.

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Original NASA ASRS Text

Title: ACR LTT RETURNS LANDS AFTER PASSENGER TELLS PIC THAT COWLING IS COMING OFF ENGINE.

Narrative: THE L ENG COWLING CAME LOOSE AND WAS HELD ON THE ACFT BY ONE CAM LOCK. I PERSONALLY PREFLTED THIS ACFT, AND CHKED THE SECURITY OF THE ENG COWLING AS WELL AS THE FOUR LOCK, UNLOCK ALIGNMENT MARKS ON THE CAM LOCK NUTS. THE ACFT WAS LANDED AND BROUGHT BACK TO THE GATE AREA. SOME COMPANY MECHS MET THE ACFT, AND A STATEMENT WAS MADE BY ONE OF THE MECHS THAT IT WAS POSSIBLE FOR THE LOCK, UNLOCK ALIGNMENT MARKS TO BE IN THE LOCKED POS, AND THE COWLINGS SEEM SECURE, BUT THE ONLY WAY TO MAKE SURE THE COWLING WAS SECURE IS TO GET A WRENCH AND TURN THE CAM LOCK NUTS AND FEEL THE DETENT IN THE CAM LOCK ITSELF. THE COMPANY OPS MANUAL AND PROCS PROHIBIT PLTS FROM DOING THIS. I PERSONALLY FEEL THAT THERE SHOULD BE MORE FASTENERS TO HOLD THE COWLING IN PLACE AND A BETTER WAY TO VERIFY THE SECURITY OF THE COWLING. ON LNDG THE PARTIALLY SECURE COWLING WAS BUMPING UP AGAINST THE PROP GOVERNOR, MAKING THE PROP GO TO THE GND, LOW PITCH STOP. CAUSING A BIG YAW WHEN THE PWR WAS REDUCED FOR LNDG. SUPPLEMENTAL INFO FROM ACN 171218. F/O DID THE PREFLT AND I WALKED AROUND THE ACFT ALSO. THE L ENG COWLING WAS SECURE AND CAM LOCKS WERE IN THE LOCKED POS, MY F/O PUSHED AND PULLED ON THE COWLING, IT WAS SECURE. DURING CLBOUT A PAX CAME FORWARD AND INFORMED US THAT L COWLING IS COMING OFF, WHEN I CHKED IT WAS HANGING ON BY ONE LOCK. WE DID NOT DECLARE AN EMER, JUST TOLD ATC THAT WE NEEDED TO LAND IMMEDIATELY.

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.