Robinson R44 II N168AG accident near Topanga, California

Probable cause

The in-flight separation of the tail rotor gear box for an undetermined reason. Contributing to the accident was the hilly terrain, which was unsuitable for a forced landing.

NTSB analysis

About 15 minutes into the helicopter's local sightseeing flight, the pilot heard a loud noise and the helicopter began to rotate to the right. He entered an autorotation and aimed for a trail in the hilly terrain the helicopter was passing over. As he flared the helicopter and pulled up on the collective to terminate the autorotation, the helicopter again began to rotate to the right. The helicopter impacted the trail and rolled over, coming to rest on its right side. Examination revealed that the tail rotor gearbox had separated from the tail boom. With the exception of the outboard sections of both tail rotor blades, none of the tail rotor components were recovered. The blade sections were found along the helicopter's flight path about 1/2-mile from the accident site. The two blade sections both displayed signatures consistent with the tail rotor contacting the helicopter's vertical stabilizer after the tail rotor gear box separated from the tail boom. The reason for the separation of the tail rotor gear box could not be determined due to the missing parts.

Text from the NTSB. Open the NTSB docket for LAX08LA183 for the full record.