What happened
On 2 November 2009, a Robinson R22 Beta helicopter, registration ZS-HAN, was performing a private takeoff from Rand Airport. The pilot, who was flying to accumulate hours for a commercial license, was accompanied by one passenger. As the aircraft began its takeoff roll and gained altitude and airspeed, the low main rotor RPM warning horn activated and the corresponding warning light illuminated.
In an attempt to manage the situation, the pilot applied more throttle to recover the lost RPM, but the engine failed to compensate. Faced with nearby trees and electrical cables, the pilot decided to abandon the takeoff. To maximize the available skidding distance, the pilot attempted to maintain altitude while reducing speed. Because the aircraft was already at a very low altitude, the pilot could not lower the collective and instead used the cyclic to keep the helicopter level while slowing down.
The aircraft eventually made contact with the ground at the threshold of runway 17. The helicopter skidded for approximately 7 meters before the left skid caught the grass shoulder at the edge of the runway. This impact caused the helicopter to roll onto its left side, at which point the main rotor blades struck the ground.
The investigation
SACAA AIID investigators examined the aircraft and the circumstances surrounding the flight. The investigation confirmed that the engine was in good working order, as a ground test performed by an approved maintenance organization found the powerplant to be operating normally. The aircraft's maintenance records were found to be in compliance with all necessary regulations, and the pilot held a valid license and medical certificate.
Findings
- The aircraft was overloaded by 24.11 lbs at the time of the accident.
- The engine and airframe were found to be in a serviceable condition.
- Weather conditions were favorable and were not a contributing factor.
- The primary cause of the roll was that the left skid dug into the grass shoulder during the landing roll.
- It was noted that the pilot may have utilized improper takeoff techniques, which led to the initial drop in main rotor RPM.