What happened
On April 14, 2018, a DG-400 glider, registered as HB-2070, was performing a private VFR flight at St. Gallen-Altenrhein (LSZR). During the approach to grass runway 28, the pilot experienced a sudden failure in radio communications. While the pilot could still receive transmissions, they were unable to transmit any outgoing messages.
At the same time, a glider tow operation was preparing for departure on the same grass runway. Because the pilot could not communicate with the tower or other aircraft to coordinate the landing, they chose to avoid flying over the departing tow setup. To maintain safety, the pilot opted to land on a nearby meadow characterized by tall grass.
Upon touching down, the aircraft traveled approximately ten meters before a sudden 180-degree yaw occurred in the tall grass. The impact resulted in light damage to the aircraft, specifically a cracked fuselage and a bent tailwheel. The pilot was not injured.
The investigation
The investigation focused on why the radio equipment failed despite passing pre-flight checks. While the pilot reported the radio was functioning correctly before takeoff, the inability to send "blind calls" during the approach necessitated the emergency landing decision.
Technical inspection of the radio equipment during repair work revealed that the installation was otherwise sound, but a broken solder joint had developed on the push-to-talk (PTT) button. It is believed that the physical vibrations and movements of the control stick during flight caused the previously intact electrical connection to fail mid-flight.