What happened
During a skydiving operation, a pilot was conducting training for a second pilot on the operation of the aircraft. Following six successful flights, the crew completed the deployment of skydivers on the final flight without initial incident. As the aircraft descended toward the landing site with the engine at idle power, the aircraft performed a 360-degree right turn after turning onto final approach, likely due to excessive altitude.
During the approach, the aircraft experienced a series of oscillations in both speed and thrust. The pilot attempted to adjust the throttle, but the engine power did not respond as anticipated. While attempting to avoid a berm located in the flight path of a nearby dirt field, the pilot maneuvered the aircraft into a right turn. The aircraft subsequently landed short of the runway and struck the berm. At the moment of impact, the engine was producing power. There were no mechanical failures or malfunctions identified in the aircraft following the crash.
Findings
Investigation into the flight data and engine characteristics suggests that the aircraft, which had been modified with a Honeywell TPE331 engine, was subject to specific operational complexities. Because the engine was operating near the transition between propeller-governing and underspeed-governing modes, the throttle sensitivity was significantly increased. Small movements of the power lever can cause large, unexpected changes in thrust.
It is believed that the pilot experienced pilot-induced oscillations (PIO) due to this high sensitivity during the final approach. The investigation noted that the pilot in the left seat may have been unable to clearly monitor engine power changes because she was listening to music at a high volume through her headset. It is also unclear exactly when the pilot in the right seat took control of the aircraft, though the oscillations occurred during the period when the left-seated pilot was likely at the controls. The accident resulted in no reported fatalities, though the right-seated pilot sustained injuries.