Accident Overview
On April 27, 2009, a Robinson R22 Beta helicopter, registration JA7987, operated by Osaka Aviation Inc., was conducting flight training at Yao Airport. The aircraft had taken off at approximately 14:40 Japan Standard Time for a training flight that included air work and takeoff and landing practice. The crew consisted of a captain (instructor) and a trainee.
Sequence of Events
After completing air work training, the aircraft returned to Yao Airport for takeoff and landing exercises. The crew performed a normal landing and two straight autorotation power recoveries. While preparing for a 180° turn autorotation power recovery, the instructor observed that the trainee initiated the turn too early and corrected the cyclic position. Shortly after, the instructor felt unusual impacts and noticed the oil pressure warning light illuminated, leading him to judge that the engine had stopped. The altitude was approximately 350 feet.
The instructor took over control and decided to land on a grass field adjacent to the runway rather than attempt to reach the runway, as he believed a landing on the runway would result in a severe impact. He reported the engine stoppage to air traffic control and executed a landing on the grass. The rotor low rotation warning sounded during the descent. The landing was hard, but the helicopter did not overturn.
Post-Accident Findings
After landing, the instructor checked the fuel indicator, mixture knob, ignition switch, and fuel shut-off valve, all of which were in their normal positions. The trainee reported that the fuel load at takeoff was approximately 19.2 gallons in the main tank and two-thirds of the 10.5-gallon sub-tank, providing an endurance of about 2 hours 40 minutes. The trainee had used the carburetor heat knob during training due to indications in the yellow arc of the carburetor temperature indicator.
Both occupants were not injured. The aircraft sustained substantial damage, but no fire occurred. The investigation did not determine why the engine stopped.