What happened
On April 30, 2009, a YETTI J-03 ultralight aircraft, registration OK-CUX 22, was performing a flight from Bubovice airport (LKBU) with the intention of flying to Trutnov. Following takeoff from runway 28L, the pilot experienced an initial power loss at an altitude of approximately 50 meters. Although engine power was temporarily restored, allowing the aircraft to climb to 70 meters, the pilot elected to perform a safety landing at the departure airfield after determining that nearby plowed and beet fields were unsuitable for touchdown.
During the landing pattern, specifically between the third and fourth turns, the engine failed completely. While attempting to maintain gliding speed and clear a stand of trees, the aircraft lost altitude too rapidly to reach the runway. The aircraft struck bushes at the edge of a sloping meadow approximately 400 meters from the threshold of runway 28L and impacted the ground from a height of about 5 meters. The aircraft slid 20 meters along the ground before coming to a halt. The pilot sustained no injuries, though the aircraft suffered extensive damage, including a destroyed landing gear, damaged engine firewall, and structural damage to the fuselage and right wing.
The investigation
The ÚZPLN investigation focused on the mechanical state of the engine and fuel systems. Investigators conducted fuel flow tests on the aircraft's dual electric fuel pumps and filters. These tests demonstrated that the fuel delivery system was functioning correctly, with a flow rate of 82.8 liters per hour—more than double the required minimum of 31.25 liters per hour. No defects were found in the pumps or the fuel filter during these post-accident examinations. The investigation also reviewed the pilot's qualifications, flight experience, and the meteorological conditions, which included recent rain showers and broken clouds.
Findings
- The primary cause of the accident was likely an unreliable fuel supply to the engine.
- The pilot's options for an emergency landing site were severely limited due to the unsuitable terrain of the surrounding fields.
- The aircraft was unable to reach the runway due to insufficient altitude following the engine failure.
- The aircraft sustained significant structural damage upon impact with the vegetation and ground.