Narrative:

I was on a repos flight with only a mechanic on board when the right engine cowling came up and was struck by the main rotor blades. The cowling departed the aircraft and the pieces landed in a tree and on a street in a residential area. There were no injuries or property damage on the ground. We made an uneventful landing at the auxiliary pad which was our original destination. This flight was the second flight of the day for me. Upon returning from the first flight, one of the mechanics told me he wanted to do a compressor wash on the left engine. After washing the aircraft, the mechanic opened the left engine cowling and proceeded to do a compressor wash on that engine. I helped him by engaging the starter when he asked. I did this while sitting in the copilot's seat which on this helicopter is the left front seat. After he finished and said he was ready to go, I walked around the nose and climbed into the pilot's seat after glancing back briefly to make sure nothing was amiss along the right side of the aircraft. We then departed the main helipad to the south and flew a l-hand pattern en route to the auxiliary pad where we planned to conduct the engine power check. Abeam our landing point on the downwind leg, I reduced power and raised the nose slightly to decelerate and begin the approach. Almost immediately I felt in the cyclic and collective controls a strong medium frequency vibration lasting approximately 2 seconds. After the vibration stopped, I checked each of the controls and found they responded normally. I continued the approach and we landed at the auxiliary pad. After recovering what remained of the cowling, it was determined that 2 of the 5 latches had been secured prior to takeoff. This was probably done when the mechanic closed the cowling prior to washing the aircraft. I assumed that since the cowling was closed that it was completely latched. I think 2 contributing factors were: 1) poor communication between the mechanic and me, and 2) fatigue induced complacency. This was the 12TH day in a row I had worked without a day off. Being tired may have made me complacent about checking the mechanic's work by doing a complete walkaround prior to takeoff. Our company has re-emphasized to all its pilots the importance of doing this walkaround.

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Original NASA ASRS Text

Title: HELI PLT STRIKES OWN ENG COWLING AFTER IT SEPARATES FROM ACFT DURING SHORT REPOS HOP.

Narrative: I WAS ON A REPOS FLT WITH ONLY A MECH ON BOARD WHEN THE R ENG COWLING CAME UP AND WAS STRUCK BY THE MAIN ROTOR BLADES. THE COWLING DEPARTED THE ACFT AND THE PIECES LANDED IN A TREE AND ON A STREET IN A RESIDENTIAL AREA. THERE WERE NO INJURIES OR PROPERTY DAMAGE ON THE GND. WE MADE AN UNEVENTFUL LNDG AT THE AUX PAD WHICH WAS OUR ORIGINAL DEST. THIS FLT WAS THE SECOND FLT OF THE DAY FOR ME. UPON RETURNING FROM THE FIRST FLT, ONE OF THE MECHS TOLD ME HE WANTED TO DO A COMPRESSOR WASH ON THE L ENG. AFTER WASHING THE ACFT, THE MECH OPENED THE L ENG COWLING AND PROCEEDED TO DO A COMPRESSOR WASH ON THAT ENG. I HELPED HIM BY ENGAGING THE STARTER WHEN HE ASKED. I DID THIS WHILE SITTING IN THE COPLT'S SEAT WHICH ON THIS HELI IS THE L FRONT SEAT. AFTER HE FINISHED AND SAID HE WAS READY TO GO, I WALKED AROUND THE NOSE AND CLBED INTO THE PLT'S SEAT AFTER GLANCING BACK BRIEFLY TO MAKE SURE NOTHING WAS AMISS ALONG THE R SIDE OF THE ACFT. WE THEN DEPARTED THE MAIN HELIPAD TO THE S AND FLEW A L-HAND PATTERN ENRTE TO THE AUX PAD WHERE WE PLANNED TO CONDUCT THE ENG PWR CHK. ABEAM OUR LNDG POINT ON THE DOWNWIND LEG, I REDUCED PWR AND RAISED THE NOSE SLIGHTLY TO DECELERATE AND BEGIN THE APCH. ALMOST IMMEDIATELY I FELT IN THE CYCLIC AND COLLECTIVE CTLS A STRONG MEDIUM FREQ VIBRATION LASTING APPROX 2 SECONDS. AFTER THE VIBRATION STOPPED, I CHKED EACH OF THE CTLS AND FOUND THEY RESPONDED NORMALLY. I CONTINUED THE APCH AND WE LANDED AT THE AUX PAD. AFTER RECOVERING WHAT REMAINED OF THE COWLING, IT WAS DETERMINED THAT 2 OF THE 5 LATCHES HAD BEEN SECURED PRIOR TO TKOF. THIS WAS PROBABLY DONE WHEN THE MECH CLOSED THE COWLING PRIOR TO WASHING THE ACFT. I ASSUMED THAT SINCE THE COWLING WAS CLOSED THAT IT WAS COMPLETELY LATCHED. I THINK 2 CONTRIBUTING FACTORS WERE: 1) POOR COM BTWN THE MECH AND ME, AND 2) FATIGUE INDUCED COMPLACENCY. THIS WAS THE 12TH DAY IN A ROW I HAD WORKED WITHOUT A DAY OFF. BEING TIRED MAY HAVE MADE ME COMPLACENT ABOUT CHKING THE MECH'S WORK BY DOING A COMPLETE WALKAROUND PRIOR TO TKOF. OUR COMPANY HAS RE-EMPHASIZED TO ALL ITS PLTS THE IMPORTANCE OF DOING THIS WALKAROUND.

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.