Authorities said the incident did enough damage that the rotor and the top of the transmission came off the helicopter. The aircraft went down in a training area in the southeast corner of Camp Pendleton near Fallbrook.
The September crash killed two Marines and started a brush fire that burned more than 100 acres. Both pilots onboard were killed.
The report, obtained by the U-T San Diego newspaper, recommends changing the design of the AH-1W Cobra Attack helicopters to better protect them against bird strikes.
