SEA08FA185 · Robinson Helicopter R22 BETA II

The pilot, who had not flown his helicopter for about one year, took off and flew about seven to ten minutes to the location of his personal residence. Once at that location, he flew around the local area while waiting for the person who drove him to the airport to return to the newly constructed helipad at the residence before he made his first landing there. After about ten minutes of maneuvering around the area, the helicopter experienced a complete loss of engine power, and the pilot attempted an autorotation to the backyard of a residence about one-half mile from his own. During the last part of the attempted forced landing, the helicopter collided with a tree and a wood fence. The investigation did not reveal any anomalies or malfunctions that would have prevented the engine from operating normally, and the engine underwent a successful post-accident dynamometer test run. The investigation revealed that the flight took place during ambient conditions that would be expected to produce carburetor icing, and under which the pilot would need to constantly monitor the carburetor temperature gauge and make adjustments to the carburetor heat. The pilot had a history of seasonal allergies, and toxicology test results were consistent with the recent use of diphenhydramine, a sedating and impairing over-the-counter antihistamine often known by the trade name of Benadryl. The extent to which impairment from the medication may have played a role in the accident could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset