What happened
On November 26, 2011, at Mikulovice airfield, a takeoff attempt involving a SZD-50-3 Puchacz glider, registration SP-3485, and a Z 42M towplane, registration OK-JSF, resulted in two emergency landings.
During the takeoff roll from runway 23, the glider experienced a significant loss of climb performance. The pilot of the towplane, attempting to clear obstacles behind the airfield, maneuvered the aircraft to the right, which led to a flight path toward nearby residential buildings. The glider pilot, recognizing the critical situation, released the tow rope. However, the glider was already at a low altitude and low airspeed; it entered a right-hand bank and landed hard on the ground, causing the wing to strike the terrain.
Simultaneously, the towplane pilot attempted to complete the climb but was unable to maintain sufficient altitude. The towplane performed an emergency landing across the runway threshold, striking a fence and hitting utility poles, which caused extensive damage to the aircraft's fuselage, engine mount, and wings.
The investigation
The ÚZPLN investigation focused on the mechanical state of both aircraft and the actions of the crews. Investigators examined the glider's air brake mechanism and found that the control lever had not been properly locked in the closed position. This allowed the air brakes to deploy spontaneously due to aerodynamic forces and the impact of the glider's initial bounce on the runway.
Furthermore, the investigation reviewed the weight and balance of the flight. The glider's takeoff weight was calculated at 567 kg, which exceeded the 500 kg limit specified in the towplane's flight manual by 13.4%. The investigation also looked into the flight experience of the glider pilot and the operational procedures at the airfield.
Findings
- The primary cause of the accident was the spontaneous deployment of the air brakes because the control lever was not secured in the locked position.
- The glider pilot failed to recognize the cause of the decreasing airspeed and delayed the decision to terminate the takeoff.
- The towplane pilot failed to terminate the tow in a timely manner that would have allowed for a safe landing for both aircraft.
- The takeoff weight of the SZD-50-3 Puchacz exceeded the maximum allowable limit for the Z 42M towing equipment.
- The glider pilot did not meet the required flight experience criteria for conducting a flight with an additional occupant.
- The airfield organizer failed to ensure the glider was operated by a pilot with sufficient recent experience for the specific flight conditions.