ERA15FA096 · Robinson Helicopter R22 BETA

The student helicopter pilot was on a solo training flight in the airport traffic pattern. He had completed eight approaches via a right downwind approach to the runway, when the air traffic controller advised him that he was number three for his next approach. About 1 minute later, the student pilot requested a left 360-degree turn. The controller then instructed him to hold at his current location and expect to be number four in sequence. During the next 6 minutes, the controller made three attempts to have the student pilot report the traffic to follow on final approach in sight, and the student pilot advised that it was hard for him to hear the controller's instructions due to wind noise. The controller then advised the student pilot to follow an airplane on short final approach, and the student pilot reported the traffic in sight. About 1 minute later, the controller advised the pilot of another airplane to follow the helicopter on the approach. The airplane pilot observed the helicopter ascend in a series of right, 360-degree turns for about 100 to 200 ft. As it climbed, white smoke consistent with a rapid increase in engine rpm and an engine overspeed trailed the helicopter. When the helicopter climbed to an apex of about 800 ft, the ends of both rotor blades coned upward to where the tips were nearly vertical, consistent with a low rotor rpm condition. The helicopter then entered a right, spiraling descent until it impacted the water.

A postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The main rotor blade elastomeric teeter stops were missing, consistent with low rotor rpm blade flapping. Although the temperature and dew point were conducive to carburetor icing, its formulation likely would not have allowed the helicopter to climb as high as it did just before the accident. More likely, the student pilot became distracted while he attempted to track other aircraft in the traffic pattern and sequence the helicopter for the approach, which led to his failure to maintain rotor rpm. Toxicological testing performed on specimens from the pilot identified butalbital in liver (1.24 ug/g) and in muscle (0.468 ug/g). Estimated corresponding blood levels were likely below the therapeutic window for butalbital, and unlikely to have been directly impairing at the time of the accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset