What happened
On 1 June 2018, a flight instructor and a student pilot were conducting circuit training at Klipriver Airfield in Gauteng Province. The flight was part of a type conversion exercise in a modified Chayair Sycamore MK1 gyroplane, registration ZU-BUA. After completing several successful take-offs and landings, the aircraft was performing its tenth touch-and-go maneuver at an altitude of approximately 80 to 150 feet.
During this maneuver, the student pilot noticed a distinct, rhythmic knocking sensation through the control column. The instructor immediately took command of the aircraft and prepared for an emergency landing, instructing the student to shut down the engine. However, roughly 10 seconds after the instructor assumed control, the engine stopped unexpectedly. While attempting a 90-degree banked turn to avoid power lines, the pilot lost control, and the aircraft entered a violent right-hand spiral. The gyroplane struck the ground heavily, resulting in substantial damage to the landing gear, tail section, and rotor blades. The instructor sustained minor injuries, while the student pilot escaped without injury.
The investigation
The SACAA AIID investigation examined the aircraft' and the circumstances leading to the impact. Investigators noted that the aircraft had undergone significant modifications, including the installation of a heavier Subaru EJ25 engine, which had increased the aircraft's empty weight from 380 kg to 446 kg. To compensate for a nose-heavy center of gravity, the mast plate had also been modified.
Analysis of the weight and balance revealed that the aircraft was operating above its maximum allowable limit. With the combined weight of the two occupants and 35 liters of fuel, the takeoff weight was approximately 632 kg, exceeding the maximum all-up weight of 590 kg by 7%. Following the crash, the engine was tested and found to be functioning normally, leaving the cause of the mid-air shutdown a mystery.
Findings
- The primary cause of the accident was an engine stoppage in flight for reasons that could not be determined.
- The aircraft was operating in an overweight condition, exceeding its maximum certified takeoff weight.
- The aircraft's center of gravity had been adjusted via mast plate modifications to account for the heavier engine installation.