Accident Summary
On 13 February 2015 at 1113 UTC, a Robinson R22 Beta (registration G-THLA, serial number 3462, year of manufacture 2003) equipped with one Lycoming O-360-J2A piston engine was involved in an accident during a training flight. The helicopter came to rest on its right side in a ploughed field off Snargate Lane, Romney Marsh, Kent. Both occupants, the instructor (holder of a Commercial Pilot’s Licence, age 37, with 960 total flying hours including 857 on type) and a student, were uninjured. The helicopter sustained substantial damage to the rotor system and tailboom.
History of the Flight
The flight was conducted to focus on autorotation techniques in preparation for the student’s General Flying Test. The instructor reported wind from 150/160° at 25–30 kt, a cloud base above 2,000 ft, and hazy visibility. The sortie began with two gentle autorotations completed satisfactorily, followed by advanced exercises including constant attitude, standard (60 kt) range, and extended range autorotations. The instructor then demonstrated a 360° autorotation, explaining how the 30 kt headwind would push the helicopter back and that airspeed and rotor rpm would decrease during the turn. He completed the demonstration with a flared recovery at about 55 kt.
The student initiated her autorotation at the correct position for a chosen landing area different from the instructor’s. She entered a left turn and lost airspeed as predicted. During the turn, the low rotor rpm warning horn sounded (rotor rpm below 96%). The student lowered the collective pitch control to restore the rpm needle to the green sector. When the helicopter lined up for the landing field, the instructor noted airspeed slow and height about 250 ft. He joined the engine and rotor rpm needles by applying power and instructed the student to go around. After 2–3 seconds, he applied considerably more power, then full power as the helicopter descended to about 150 ft, and pushed forward on the cyclic to gain airspeed. The helicopter continued to descend, and the instructor attempted a flare at approximately 40 ft for a low-speed landing on the ploughed surface. The skids dug in, the main rotors struck the ground, and the helicopter rolled onto its right side. The instructor turned off fuel and electrics, noting fuel escaping from the cowling around the rotor head. Both occupants exited without assistance.
Discussion
The instructor stated that he believed the helicopter experienced severe windshear in the final stage of the autorotation, causing a loss of lift that prevented a recovery or go-around. The instructor’s report indicated that a high rate of descent developed compared to the demonstrated autorotation, possibly originating from the reduction in collective pitch following the low rotor rpm warning. The reduction in airspeed may have resulted from windshear, but with height decreasing rapidly, the instructor lowered the nose to increase airspeed, further increasing the rate of descent. The cloud base of 2,000 ft could have allowed a higher entry to the autorotation, giving more time to choose a suitable landing area, but the instructor noted the student had performed well previously and was capable of advanced manoeuvres. Several potential landing areas were missed while the instructor was explaining which field to aim for, resulting in lineup on the ploughed field. The instructor stated he had intended to go around from approximately 300 ft.
The report also noted that flight conditions may have been conducive to vortex ring state, which requires high rate of descent (typically >300 ft/min), applied power, and low airspeed. The instructor, upon further reflection, stated he was confident the go-around was initiated at 45 kt accelerating toward 60 kt, the ideal point on the power curve to arrest descent, and concluded that vortex ring did not contribute to the accident.