Narrative:

Our commuter flight on jul/xy/98 started out with a mechanical delay involving an oil leak on the right engine. The fix involved taking the airplane across the field to the maintenance ramp where the mechanic began his repairs by removing the majority of the right engine's cowlings. The leak was fixed and all of the cowlings, zeus fasteners, cam locks, and safety wires were reattached, as I, the captain of the flight, observed. I followed up with a preflight, and then taxied back to the terminal ramp, where my copilot also performed a successful preflight. The scheduled flight boarded approximately 5 hours late with 3 passenger. Takeoff and climb were both uneventful, with all engine instruments indicating normal. We leveled off at 15000 ft MSL and set cruise power. Approximately 20 mins and 50 mi into the flight, I, the PF, and the copilot noticed a slight bump in what was otherwise smooth air. As the copilot looked out his right window, he noticed that the top forward, inboard attaching points (cam locks) had come loose, causing 2 safety wires to break. This resulted in the upper cowling separating from the lower cowling approximately 4 inches. There is no emergency or abnormal procedure for this condition, so I immediately slowed down to 150 KIAS, just above vg in order to minimize pressure on the cowling. We returned to ZZZ, requesting only priority handling -- no emergency. Upon landing, we shut down the engines before attempting to taxi to the ramp. By this time the cowling had settled back down onto the main structure, and had been held on by 2 other cam locks and safety wires. However, the leading edge was uncomfortably close to the spinner. We restarted only the left engine and taxied to the ramp. The original mechanic met us at the gate, inspected the engine, and reattached the cowling.

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Original NASA ASRS Text

Title: A BEECH 1900D IN CRUISE AT 15000 FT DIVERTED DUE TO #2 ENG UPPER FORWARD COWLING LOOSE AND RAISED, CAUSED BY IMPROPER INSTALLATION AFTER MAINT.

Narrative: OUR COMMUTER FLT ON JUL/XY/98 STARTED OUT WITH A MECHANICAL DELAY INVOLVING AN OIL LEAK ON THE R ENG. THE FIX INVOLVED TAKING THE AIRPLANE ACROSS THE FIELD TO THE MAINT RAMP WHERE THE MECH BEGAN HIS REPAIRS BY REMOVING THE MAJORITY OF THE R ENG'S COWLINGS. THE LEAK WAS FIXED AND ALL OF THE COWLINGS, ZEUS FASTENERS, CAM LOCKS, AND SAFETY WIRES WERE REATTACHED, AS I, THE CAPT OF THE FLT, OBSERVED. I FOLLOWED UP WITH A PREFLT, AND THEN TAXIED BACK TO THE TERMINAL RAMP, WHERE MY COPLT ALSO PERFORMED A SUCCESSFUL PREFLT. THE SCHEDULED FLT BOARDED APPROX 5 HRS LATE WITH 3 PAX. TKOF AND CLB WERE BOTH UNEVENTFUL, WITH ALL ENG INSTS INDICATING NORMAL. WE LEVELED OFF AT 15000 FT MSL AND SET CRUISE PWR. APPROX 20 MINS AND 50 MI INTO THE FLT, I, THE PF, AND THE COPLT NOTICED A SLIGHT BUMP IN WHAT WAS OTHERWISE SMOOTH AIR. AS THE COPLT LOOKED OUT HIS R WINDOW, HE NOTICED THAT THE TOP FORWARD, INBOARD ATTACHING POINTS (CAM LOCKS) HAD COME LOOSE, CAUSING 2 SAFETY WIRES TO BREAK. THIS RESULTED IN THE UPPER COWLING SEPARATING FROM THE LOWER COWLING APPROX 4 INCHES. THERE IS NO EMER OR ABNORMAL PROC FOR THIS CONDITION, SO I IMMEDIATELY SLOWED DOWN TO 150 KIAS, JUST ABOVE VG IN ORDER TO MINIMIZE PRESSURE ON THE COWLING. WE RETURNED TO ZZZ, REQUESTING ONLY PRIORITY HANDLING -- NO EMER. UPON LNDG, WE SHUT DOWN THE ENGS BEFORE ATTEMPTING TO TAXI TO THE RAMP. BY THIS TIME THE COWLING HAD SETTLED BACK DOWN ONTO THE MAIN STRUCTURE, AND HAD BEEN HELD ON BY 2 OTHER CAM LOCKS AND SAFETY WIRES. HOWEVER, THE LEADING EDGE WAS UNCOMFORTABLY CLOSE TO THE SPINNER. WE RESTARTED ONLY THE L ENG AND TAXIED TO THE RAMP. THE ORIGINAL MECH MET US AT THE GATE, INSPECTED THE ENG, AND REATTACHED THE COWLING.

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.