What happened
On April 21, 2020, at Hran andice Airport (LKHN), a Zlín Z-526 F, registration OK-EHO, was performing a glider tow operation involving an L-13 glider. The flight was part of a training program for the pilot to obtain a TOWING-S qualification, with an instructor on board.
During the third takeoff attempt of the day, the pilot increased engine power to takeoff settings. As the aircraft accelerated and the landing gear unloaded, the gear retracted. This occurred approximately 30 meters into the takeoff roll, before the glider had released from the tow line. The sudden retraction caused the aircraft to settle onto its belly, leading to propeller contact with the runway surface and a subsequent impact with the ground. The glider pilot successfully released the tow line, performed a left turn, and landed safely on the airfield.
The investigation
The ÚZPLN investigation examined the actions of the crew, the mechanical state of the aircraft, and the environmental conditions. The investigation established that the pilot had performed several successful tow operations earlier that day. However, after landing the second tow, the pilot exited the aircraft to detach the tow line and then re-entered the cockpit to prepare for the third flight.
Investigators found that the pilot's attention was compromised by fatigue and the physical and mental strain of conducting training while adhering to COVID-19 safety protocols, including wearing a face mask. The investigation also noted that the instructor, seated in the front cockpit, was unable to visually verify the position of the landing gear switch, which is located in the rear cockpit.
Findings
- The primary cause of the accident was the pilot's error in accidentally switching the landing gear to the 'UP' position during cockpit preparations.
- The pilot's fatigue and the added stress of wearing a mask during the training session contributed to the oversight.
- The Zlín Z-526 F sustained extensive damage, including significant damage to the fuselage structure, the left landing gear leg, the engine, the propeller blades, and the left wing.
- There were no injuries to the crew, and no damage was caused to third-party property.