ERA13FA070 · Robinson Helicopter R22 BETA II

The helicopter was in cruise flight about 500 feet above ground level, over a bay beach, when both of its main rotor blades separated. The helicopter subsequently descended into the bay, and the wreckage with the exception of the main rotor blades was recovered 2 days later. One main rotor blade was subsequently recovered about 1 month later, and the other main rotor blade was not recovered. With the exception of the separation of the main rotor blades, examination of the airframe and engine did not reveal any evidence of preimpact mechanical malfunctions or anomalies. Metallurgical examination of the rotor hub and the recovered main rotor blade revealed features consistent with overstress, and no preexisting cracking or fatigue was noted. Additionally, damage to the teetering stops on the rotor hub was consistent with mast bumping. The observed mast bumping could have resulted from large, abrupt flight control inputs or from a mechanical failure of the unrecovered main rotor blade.

Toxicological testing and review of the pilot's medical records revealed a history of near nightly use of zolpidem (Ambien) as a sleep aid and frequent use of rizatripan (Maxalt) to treat migraine headaches. Neither condition or its respective prescription medication for treatment was reported to the Federal Aviation Administration and if it had been, would have most likely disqualified the pilot for a medical certificate based on the frequency of use/symptoms; however, the investigation could not determine the effects, if any, that the recurrent migraine, chronic zolpidem use, and underlying sleep problems might have had on the pilot at the time of the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset