Narrative:

This is a news/traffic helicopter and we had been called to a breaking news story. Our regular helicopter had just been grounded for maintenance; so the back up helicopter had to be made ready for flight. After 5 minutes I was told it would take just as long to complete the paperwork for the back-up ship as it would to disable and MEL our regular aircraft. We opted for the latter. So the photographer and I had to move all the items from the back up ship (which we just put in there) back to the regular helicopter. I did my pre-flight and walk around; got in and took off.we got to the scene; got our footage; and left. Just as I turned to leave the cowling of helicopter came open in flight requiring a precautionary landing in an open football field. Upon inspection on the ground it was discovered the cowling had come in contact with the sleeves of the rotor blades damaging 2 of the 3 sleeves and the cowling itself. This required our mechanic to be brought to the field with the necessary parts to do a field repair as the aircraft was un-airworthy to fly.it is unclear as to how or why the cowling became unlatched; but prior to the incident maintenance had been performed on the aircraft in question; paperwork had to be completed and a shift of crew and items from the back-up helicopter to the helicopter involved all played a roll in the cowling opening in flight. The mechanic said he left the cowl up; but as I did my preflight I saw the cowling was down and thought it was latched. So we are unsure of how it came open.

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Original NASA ASRS Text

Title: Following a departure complicated by numerous factors including maintenance deferrals and an aborted aircraft change; the helicopter took off; completed its mission and then suffered an inflight opening of the engine cowling forcing an emergency landing and causing damage to the cowling and the rotor blade sleeves.

Narrative: This is a news/traffic helicopter and we had been called to a breaking news story. Our regular helicopter had just been grounded for maintenance; so the back up helicopter had to be made ready for flight. After 5 minutes I was told it would take just as long to complete the paperwork for the back-up ship as it would to disable and MEL our regular aircraft. We opted for the latter. So the photographer and I had to move all the items from the back up ship (which we just put in there) back to the regular helicopter. I did my pre-flight and walk around; got in and took off.We got to the scene; got our footage; and left. Just as I turned to leave the cowling of helicopter came open in flight requiring a precautionary landing in an open football field. Upon inspection on the ground it was discovered the cowling had come in contact with the sleeves of the rotor blades damaging 2 of the 3 sleeves and the cowling itself. This required our mechanic to be brought to the field with the necessary parts to do a field repair as the aircraft was un-airworthy to fly.It is unclear as to how or why the cowling became unlatched; but prior to the incident maintenance had been performed on the aircraft in question; paperwork had to be completed and a shift of crew and items from the back-up helicopter to the helicopter involved all played a roll in the cowling opening in flight. The mechanic said he left the cowl up; but as I did my preflight I saw the cowling was down and thought it was latched. So we are unsure of how it came open.

Data retrieved from NASA's ASRS site as of April 2012 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.