What happened
On July 5, 2020, a pilot conducted a technical test flight in an ultralight KR-2S, registration OM-M5 and 549, following a recent engine replacement. The flight was intended to verify the performance of the new Corvair engine and Varp Drive propeller. After performing three ground runs, the pilot initiated a takeoff from the left side of runway DS 3 at Krosno (EPKR) airport, approximately 300 meters from the threshold.
During the initial climb, at an altitude of approximately 35 meters, the aircraft transitioned from a climb to level flight and then began to descend despite the engine operating at full power. While attempting a left turn to avoid buildings, the pilot spotted a meadow and decided to attempt an emergency landing there. During the subsequent turn back toward the meadow, the aircraft's right wing struck a roadside lamp post. The impact caused the aircraft to rotate 180 degrees before crashing into a private property, where it struck a fence, a car, and a garage wall. The pilot sustained serious injuries, and the aircraft was destroyed.
The investigation
The PKBWL investigation examined the aircraft's engine, propeller, and documentation. Investigators found that the engine was functioning normally, though evidence of a rich fuel mixture was present in the exhaust and spark plugs. The investigation focused heavily on the propeller configuration and the takeoff parameters. The team also reviewed the aircraft's maintenance and flight logs, noting discrepancies between the recorded flight hours and the owner's statements, as well as inconsistencies regarding the engine installation history.
Findings
- The primary cause of the accident was the decision to initiate the takeoff from a position that did not allow for a safe emergency landing in the event of an engine failure or performance issue.
- The propeller pitch angle had not been correctly adjusted for the aircraft's flight speed; at speeds exceeding 120 km/h, the propeller began to act as an aerodynamic brake, causing the sudden descent.
- The pilot's takeoff roll was intentionally extended to "feel" the aircraft, which reduced the available runway distance for a safe abort.
- The pilot was operating with an expired pilot license from the Slovak Federation of Ultralight Flying (SLUF).
- No formal request for permission to conduct the technical flight had been submitted to the SLUF, rendering the flight unauthorized under their regulations.
- There were significant discrepancies in the aircraft's documentation regarding engine type and total flight hours.
- The propeller pitch angle was not properly regulated for the intended flight envelope.