What happened
On August 12, 2023, during the "II Królewski Piknik Lotniczy" airshow at Borki airfield, a prototype JK-3 Juan gyrocopter was performing a series of demonstration maneuvers. The flight profile included low-altitude passes, turns, and speed demonstrations, culminating in an autorotative landing with the engine shut down.
At approximately 16:44 LMT, while flying southeast along the runway at an altitude of roughly 100 meters, the pilot deactivated the engine. The planned landing maneuver involved a 180-degree turn to approach the runway from a northwesterly direction into a crosswind. During the descent, the pilot observed that the aircraft was descending more rapidly than anticipated. Upon completing the 180-degree turn, the gyrocopter touched down on all three landing gear wheels simultaneously and bounced off the ground. After bouncing, the aircraft traveled several meters along the runway axis. Due to the lack of airflow over the rotor caused by the inactive engine, the aircraft became uncontrollable and began veering to the right into the wind. The gyrocopter subsequently overturned onto its left side, causing significant damage to the main rotor and the airframe structure. The pilot sustained no injuries and exited the aircraft unassisted.
The investigation
The PKBWL examined the flight sequence and the technical performance of the aircraft during the engine-off maneuver. The investigation focused on the aircraft's behavior during the autorotative approach and the loss of directional control following the ground bounce.
Findings
- The primary causes of the accident were the shutdown of the engine during flight and an incorrect assessment of the gyrocopter's flight characteristics during the engine-off phase.
- A contributing factor was that the aircraft was a recently introduced prototype of a new design.
Safety action
The investigation led to the adoption of several preventive measures for the JK-3 Juan user manual, including:
- Re-establishing the H-V2 (height-velocity) diagram specifically for engine-off flight.
- Recommending that landings below 50 meters be performed in a straight line without turns.
- Including a warning regarding the reduced effectiveness of the rudder during engine-off flight.
- Recommending that, whenever possible, landings should be performed into a headwind.