What happened
On June 12, 2008, a Rombach Special biplane, registration HB-YNG, was conducting a solo training flight near the Lommis airfield in Switzerland. The pilot had previously completed several training circuits with an instructor earlier that day. During the takeoff roll for a solo circuit, the pilot applied power, but the engine experienced a momentary drop in power due to a rapid throttle increase. After a successful subsequent circuit with the instructor, the pilot attempted a solo circuit.
During the initial climb, at an altitude of approximately 100 meters, the engine suddenly lost power and eventually ceased functioning entirely. Given the low altitude, the pilot opted not to attempt a restart and instead executed an immediate emergency landing in a field west of the airfield. The aircraft touched down at the edge of a field and entered a wheat field, where the resistance caused the aircraft to nose over. The pilot escaped the wreckage without injury, though the aircraft sustained heavy damage.
The investigation
Investigators examined the aircraft's mechanical systems and fuel components. The fuel selector, electric pump, and fuel lines showed no signs of damage, and the fuel tanks were more than two-thirds full. Analysis of fuel samples confirmed the quality was within specifications. The propeller damage indicated the engine was at a low RPM upon impact.
While the engine showed internal mechanical damage during a manual rotation, investigators decided against a full ground run because such a test would likely have caused further severe damage to the engine. Because the aircraft was slated for repairs that were not immediately planned, the investigation was concluded without a definitive determination of the engine failure's root cause.