History of Flight
On 1 August 2015, a Robinson R44 helicopter (registration ZS-SBM) departed Wonderboom Aerodrome (FAWB) at 0830Z for a training flight under Part 141. The flight instructor and a student pilot intended to practice circuits and autorotations at Aeropark Zynkraal airfield before returning to FAWB. The flight to Aeropark via Bronkhorspruit dam was uneventful.
Upon arrival, the student pilot performed one circuit. On final approach for runway 27, the student initiated an autorotation into the wind. At approximately 200 feet above ground level (AGL), the main rotor revolutions per minute (RPM) began to decay. The instructor took control, lowered the collective, and opened the throttle in an attempt to recover rotor RPM. The engine laboured but rotor RPM did not increase. At about 100 feet AGL, the instructor flared the helicopter and then levelled it, but rotor RPM remained insufficient. The instructor opted for a run-on landing; the helicopter shook violently, the left-hand skid struck the ground and broke off. The main rotor blades struck the runway three times, severing the tail boom. The helicopter rolled onto its left side and came to rest on the centre of the runway.
Injuries to Persons
Neither the instructor nor the student sustained any injuries.
Damage to Aircraft
The helicopter sustained substantial damage to the main rotor blades, tail boom, left-hand skid, fuselage, and windshield.
Personnel Information
The instructor, aged 29, held a Commercial Pilot Licence (Helicopter) with a Grade 2 Flight Instructor rating and had a total flying experience of 2022.1 hours, including 747.0 hours on type. The student pilot, aged 40, held a Student Pilot Licence and had 36.5 total flying hours, with 7 hours on type.
Aircraft Information
The accident helicopter was a Robinson R44 II (serial number 12099, manufactured in January 2008) with a Textron Lycoming engine. Total airframe time at the time of the accident was 988.8 hours. The last maintenance inspection was performed on 25 June 2015 at 944.8 hours. The helicopter had a valid Certificate of Airworthiness and Certificate of Registration.
Meteorological Information
Wind was light and variable (less than 5 knots), visibility 10 km, temperature 15°C, and no cloud cover.
Wreckage and Impact Information
The helicopter came to rest on the centre of runway 27 at Aeropark Zynkraal (coordinates S 25°54'11.44", E 028°32'44.63"). The main rotor blades struck the runway three times, leaving marks consistent with a rotor system hitting the tail boom at moderate RPM. The tail boom was cut into pieces. The accident occurred during daylight.
Probable Cause
The probable cause was a hard landing following unsuccessful autorotation practice. A contributing factor was incorrect autorotation technique.