What happened
On March 8, 2013, a pilot conducted a flight from the Rottweil-Zepfenhan airfield (EDSZ) in a Trixy Aviation G 4-2 RT autogyro. After completing two circuit patterns, the pilot departed the airfield toward the north. Witnesses near the villages of Leidringen and Dautmergen observed the aircraft flying over a wooded area, noting unusual engine noises that abruptly ceased. Observers described seeing the aircraft oscillating side-to-side before pitching forward into a vertical dive. One witness reported seeing the rotor stop spinning while the aircraft rotated around its longitudinal axis. Debris was seen falling from the sky, and the wreckage was later located in a forest. The pilot sustained fatal injuries in the crash.
The investigation
The BFU examined the wreckage and analyzed flight data from the aircraft's digital cockpit display. The investigation focused on the structural integrity of the rotor head, the control linkages, and the canopy locking mechanism. Metallurgical analysis of the control rod ball joints was conducted at the Technical University of Braunschweig. Investigators also reviewed the aircraft's maintenance history, noting a previous incident involving a damaged tail rotor assembly. The investigation also examined the cockpit's digital logs, which recorded GPS coordinates, acceleration, and engine parameters.
Findings
Investigators determined that the aircraft was flying in a state "behind the power curve," characterized by significant speed fluctuations and a loss of altitude. While the engine data appeared normal, the aircraft suddenly entered a roll into a nearly inverted position followed by a massive descent.
Crucially, the investigation found that the canopy was not fully secured. Evidence showed that the forward locking block had been torn from the fuselage. The investigation concluded that the pilot may have unbuckled his harness to attempt to re-secure the large canopy during flight. This action, or the sudden opening of the canopy due to the insecure latch, likely caused a sudden disruption of the control linkages, leading to the total loss of control. Although one ball joint showed signs of a potential fatigue crack, it was ruled out as the primary cause of the accident.
Safety action
Following the accident, the manufacturer announced several safety measures. These include installing a reminder sign inside the cockpit to ensure the canopy is closed and locked before taxiing. Additionally, the manufacturer plans to replace all existing and future ball joints with forged, more vibration-resistant components and will implement a policy to replace all control linkages following any "blade flapping" event.