What happened
On June 1, 2021, at approximately 08:30 local time, a pilot was operating a Brändli BX-2 «Cherry», registration HB-YHT, on a private VFR flight from Bad Ragaz (LSZE) to Locarno (LSZL). The aircraft, a two-seat homebuilt design powered by a Rotax 912 ULS engine, departed from runway 30 following a standard warm-up period.
Shortly after takeoff, the pilot retracted the landing gear and flaps and switched off the electric fuel pump. Approximately 15 seconds after this action, the pilot experienced a loss of engine power. Due to nearby obstacles, the pilot identified a suitable landing site in a field approximately 700 meters northwest of the airfield. The pilot initiated a right turn and extended the landing gear. The aircraft touched down at roughly 50 knots; however, as the aircraft decelerated on the soft ground, the nose gear collapsed, causing the aircraft to roll over.
While the pilot sustained no injuries, the aircraft was heavily damaged. Bystanders had to break the cockpit canopy to extricate the pilot from the overturned aircraft.
The investigation
SUST examined the aircraft and the Rotax 912 ULS engine to identify potential mechanical failures. The investigation confirmed that the last maintenance checks, including a 100-hour/annual inspection, were completed in August 2020, with the most recent regulatory validation in March 2021.
Investigators found no evidence of technical defects in either the airframe or the engine that could explain the perceived power loss. Because the issue occurred immediately after the electric fuel pump was deactivated, the mechanical fuel pump was specifically tested. The mechanical pump was found to be performing correctly across the entire engine power range.