What happened
On 23 March 2005, a private flight was underway near Stellenbosch Aerodrome when the pilot and one passenger experienced a sudden loss of power. The flight, which involved local maneuvering within the Stellenbosch general flying area, proceeded normally until the aircraft reached the base leg of its approach. During this phase, the pilot observed a drop in engine RPM accompanied by slight vibrations, immediately followed by a total engine failure.
To manage the emergency, the pilot performed an autorotative maneuver, turning downwind over a treeline to reach an open field located approximately one nautical mile outside the aerodrome boundary fence. While attempting to cushion the landing at 40ft A/GL, a tailwind component caused the Robinson R44 (implied by type/context, though the report lists EXECUTIVE 162 F) to touch down at a higher airspeed than intended. The aircraft skidded roughly 10 meters before the front skids sank into soft ground, causing the helicopter to pitch forward. This motion caused the main rotor blades to strike the tail boom assembly, resulting in extensive damage to the blades, tail boom, and tail rotor.
The investigation
Investigators examined the mechanical state of the aircraft, noting that a 75-hour inspection had been completed on 3 January 2005, with only 12.4 hours flown since that service. The investigation focused on the electrical connections within the engine compartment to determine why the engine ceased operation.
Findings
- The investigation identified that an earth strap connecting the ignition modules was improperly secured to the left-hand seat frame.
- Instead of being attached to the engine mount bolt as required by the manufacturer, the strap was fastened with a bolt of a smaller diameter.
- This incorrect bolt provided insufficient electrical contact and possessed a much lower torque capacity than the specified hardware.
- A momentary interruption in this electrical ground caused the ignition system to fail, leading to the engine failure.