What happened
On August 21, 2015, at approximately 17:00 local time, an AirLony Skylane UL, registration OK-MUO44, crashed in the municipality of Lipno, Louny District. The aircraft was flying at a very low altitude, likely 50 meters or less, when it entered a sudden descent.
An eyewitness observed the aircraft flying from west to east at an estimated speed of 100 km/h. Shortly after, the aircraft was seen banking sharply between houses. The aircraft struck the roof and gable of a residential building, causing damage to the tiles and guttering, before hitting the ground. The impact with the building also severed a portion of the left wing and the left landing gear. Following the initial collision, the aircraft struck an overhead electrical pole and continued to slide across the terrain, eventually coming to rest near a fence.
The pilot sustained fatal injuries at the scene, while the passenger, an experienced pilot, suffered serious injuries.
The investigation
The ÚZPLN investigation focused on the flight path, the mechanical condition of the aircraft, and the pilot's actions. Investigators analyzed eyewitness testimony, examined the wreckage, and performed a graphical flight analysis.
Technical inspections of the ROTAX 912 S2 engine revealed several irregularities, including an improperly sized oil drain tube, a non-standard oil cooler, and improperly adjusted carburetors that caused fuel imbalance. While the engine was found to have been running at idle or near-idle during the impact, investigators could not definitively prove that an engine failure was the primary cause of the accident. The investigation also noted that the aircraft's technical certificate and insurance were not valid at the time of the accident, and much of the aircraft's maintenance documentation was unavailable.
Findings
- The pilot failed to maintain the minimum required VFR altitude of 300 meters (or 150 meters) above terrain.
- The aircraft was flying at an extremely low altitude, likely below 50 meters, during a maneuver.
- The probable cause of the accident was the aircraft falling during a maneuver at a very low altitude and likely low airspeed, leaving the pilot with insufficient time to recover.
- The pilot's extensive experience (over 1,500 hours) did not provide enough margin to rectify the situation due to the extreme proximity to the ground.