History of Flight
On 11 December 2014, a Robinson R44 Raven II helicopter, registration ZS-RUP, departed from a private farm near Bloemfontein, South Africa, on a ferry flight to Klerksdorp aerodrome. The flight was conducted under visual meteorological conditions in daylight. The pilot, who held a valid commercial pilot license and had 733.8 hours on type, reported that after lift-off, all power checks indicated normal operation. As the helicopter passed through transition at approximately 20 feet, the pilot heard a loud bang from the rear and observed a decrease in engine and rotor RPM, accompanied by the low-RPM horn. The pilot immediately lowered the collective, opened the throttle, and flared to regain rotor RPM but was unable to arrest the descent. To avoid the tail contacting the ground, he leveled the helicopter and pulled collective to cushion the landing.
Damage and Injuries
The helicopter bounced on first ground contact. On the second ground contact, the skids hooked on grass, and as the pilot pulled back on the cyclic to prevent a nose-over, the main rotor blades struck and severed the tail boom. No damage occurred to the fuselage, but the tail section, including the tail rotor gearbox and blades, was separated from the tail boom. The main rotor blades sustained leading-edge damage with missing pieces. Neither the pilot nor the two passengers were injured. The helicopter sustained substantial damage.
Investigation Findings
A teardown inspection of the Lycoming IO-540-AL-1A5 engine, along with tests of magnetos, spark plugs, and fuel injector nozzles, revealed no abnormalities. The engine was determined to be serviceable at the time of the accident. The reason for the power loss could not be determined. The helicopter had a valid certificate of airworthiness and was within weight limits (2407.3 lbs, 92.7 lbs below maximum). Density altitude was calculated at approximately 7000 feet with a temperature of 30°C and pressure altitude of 4482 feet. Weather conditions were fine, with calm wind and 10 km visibility.
Probable Cause
The investigation concluded that the accident resulted from an unsuccessful forced landing after an undetermined loss of engine power during take-off.