What happened
On September 15, 2019, a training flight involving a SZD-50-3 Puchacz glider, registration SP-3367, and an Aviat A-1B Husky aircraft, registration SP-TIR, resulted in an accident at Warsaw-Babice (EPBC) airport. The flight was a student training session focused on landing accuracy and winch/tow practice.
During the pre-flight sequence, the crew experienced a delay when a radio battery had to be retrieved. Following the installation of the battery, the instructor performed a check of the trim and airbrake lever. During the takeoff roll, the glider departed the ground first, followed by the towing aircraft. However, the towing aircraft failed to gain sufficient altitude or airspeed. The instructor, noticing the low airspeed, took control and released the towline to perform an emergency landing with a wind component.
While executing a 180-degree turn for the approach, the glider lost airspeed and entered a stall, striking the ground with the forward fuselage and left wing. The impact caused the fuselage to break behind the wings. The student pilot sustained serious injuries and was transported by helicopter to a hospital, while the instructor sustained light injuries. The pilot of the towing aircraft was uninjured.
The investigation
The PKBWL investigation focused on the mechanical state of the aircraft and the cockpit procedures. Investigators examined the airbrake mounting points on the left wing and found deformations. Testing confirmed that the airbrake mechanism itself was functional and that the locking mechanism was capable of securing the brakes in the closed position.
Analysis of the flight sequence revealed that the takeoff climb was impeded by excessive aerodynamic drag. The investigation also noted that the flight controller was not actively observing the takeoff at the time of the incident, and witnesses were positioned too far away to notice the configuration of the glider's airbrakes.
Findings
- The primary cause of the failure to climb was the improper locking of the airbrakes, which allowed them to deploy during the takeoff roll or immediately after liftoff.
- The student pilot failed to properly secure the airbrake lever, and the instructor failed to verify this specific setting during the pre-flight check.
- The glider entered a stall during the emergency landing approach due to a loss of airspeed.
- The instructor's attention was divided between monitoring the student's flight path and correcting student errors during the takeoff.
- The flight controller's lack of observation during the takeoff contributed to the lack of immediate awareness regarding the abnormal climb performance.