Accident Synopsis
On 13 March 2018, at approximately 1427 UTC, a Robinson R22 helicopter (registration ZS-RNW) was involved in an accident about 10 km southwest of Rand Aerodrome (FAGM). The helicopter was being used for a Part 141 training flight with an instructor and a student on board. The instructor sustained serious back injuries, while the student suffered minor injuries. The aircraft was substantially damaged.
Aircraft and Crew Information
The helicopter was manufactured by Robinson Helicopter Company and was appropriately maintained by an approved maintenance organization. The documentation was found to be valid and in order. The instructor held a valid Airline Transport Pilot Licence (ATPL) with a Grade 3 instructor rating and a type rating for the helicopter. He had a total flying time of 1552.2 hours, with 263 hours on type, and 210.1 hours as an instructor. The student pilot had 1.8 hours of flying time prior to the accident and did not hold a Student Pilot Licence, as it was not required under the applicable regulations for less than 5 hours of flying time.
Accident Sequence
The accident flight was the third training flight for the student, focusing on attitude and power changes (Exercise 5). The instructor and student took off from Rand Aerodrome at approximately 1500 UTC and flew to a helicopter general flying area about 7 nm southwest of the aerodrome. On the return flight at about 500 ft AGL, while changing the radio frequency, the instructor noticed the engine RPM was revving high. The aircraft yawed to the right and the nose pitched up. The inexperienced student unintentionally increased the throttle, causing an engine overspeed. The instructor then took control and closed the throttle fully to reduce the engine RPM. The helicopter began to descend rapidly, and the low rotor RPM warning horn sounded. The instructor was unable to flare, and the helicopter impacted the ground. A small post-impact fire, caused by hot exhaust contacting dry grass, was extinguished by a bystander.
Investigation Findings
Examination of the wreckage revealed that the governor switch was in the off position. The main rotor blades showed little damage, indicating low rotor RPM at impact. The engine was examined and found to have grass in the cylinders, suggesting it was running at impact, though the engine RPM could not be determined. The weather was not considered a factor in the accident.
Probable Cause
The pilot mismanaged the throttle followed by an unsuccessful forced landing. Poor technique and improper use of engine controls.