On June 14, 2008, about 1900 Pacific daylight time, a Robinson R44 II helicopter, N168AG, sustained substantial damage when it rolled over during a forced landing in Topanga Canyon, Topanga, California. The airline transport pilot and the two passengers received minor injuries. The helicopter was operated by Adventure Helicopter Tours, Los Angeles, California, as a 14 Code of Federal Regulations Part 91 sightseeing flight. Visual meteorological conditions prevailed, and a company flight plan was filed for the local flight that departed Whiteman Airport, Los Angeles, about 1845.

The pilot reported that the flight departed Whiteman Airport and headed towards the coast. About 15 minutes into the flight, he heard a "huge bang," and the helicopter began to rotate to the right. He entered an autorotation and aimed for a trail. 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.

The helicopter was examined at the accident site by a Federal Aviation Administration (FAA) inspector and after its recovery to the operator's hangar by the National Transporation Safety Board investigator-in-charge (IIC) and representatives of Robinson Helicopter Company. The fuselage was dented, deformed, and scratched. The main rotor blades remained attached to the rotor hub and were bent and buckled. The tail boom was separated into three sections: a forward section, measuring about 3 feet long, which remained attached to the fuselage; a middle section, measuring about 10 feet long; and an aft section, consisting of about 4 inches of tail boom with the horizontal and vertical stabilizers attached, but missing the tail rotor gear box and tail rotor hub and blade assembly. The middle section of tail boom was found with the fuselage and remained partially attached by wires. The aft section of tail boom was found about 70 feet from the fuselage. There was no evidence of main rotor contact with the tail boom.

The tail rotor gear box was not recovered. 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 leading edge impact damage, paint transfers, and deformation, which corresponded to damage to the lower trailing edge of the helicopter's vertical stabilizer. The geometry of the blade strikes indicated they occurred after the tail rotor gear box separated from the tail boom.

At the time of the accident, the helicopter had accumulated 973.3 hours total flight time. Its most recent 100-hour inspection was completed on April 24, 2008, at a total time of 878.2 hours. Review of the helicopter's maintenance records revealed that on August 4, 2007, at an unknown total time, a new tail skid was installed. The records indicated that on March 5, 2007, at a total time of 501.6 hours, the tail rotor assembly was removed "due to damage" and sent to Robinson Helicopter Company for repairs. The repair tag for the tail rotor assembly indicated that on March 13, 2007, a visual inspection was performed and one tail rotor blade was replaced. The tail rotor assembly was reinstalled on the helicopter on March 19, 2007, at a helicopter total time of 513.3 hours.