What happened
On December 31, 2023, an Aeroprakt A-22L2, registration SP-SWOZ, was participating in a local flying event at the Oborniki-Słonawy (EPOB) airfield. During the sixth flight of the day, the pilot was performing a landing approach on runway 11. While executing the approach, the pilot encountered a paramotor that had unexpectedly entered the landing straight without radio communication. To avoid the other aircraft, the pilot initiated a 360-degree right-hand turn over a wooded area.
During this maneuver, the aircraft's airspeed was near its minimum limit for the configuration with flaps retracted. As the pilot increased engine power, the aircraft's nose dropped below the horizon. In the ensuing turbulence, the pilot inadvertently adjusted the throttle, and the passenger, startled by the sudden change in attitude, braced themselves against the control stick, which partially obstructed the controls. The aircraft entered a stall and began a descending right turn, eventually striking two pine trees. The impact caused significant damage to the left wing and the propeller, and the aircraft slid along a fallen tree trunk before coming to rest.
The investigation
The PKBWL examined the wreckage, flight data, and environmental conditions. Investigators analyzed a video recording made by the passenger on a mobile phone, which allowed for the calculation of the aircraft's ground speed and bank angle. The investigation also reviewed meteorological data from the nearby EPPO station and interviewed a nearby witness who reported hearing the engine surge and then fail. The investigation confirmed that the aircraft's weight and center of gravity were within permissible limits, and no pre-existing mechanical failures were found in the control surfaces.
Findings
- The atmospheric conditions, characterized by high humidity and specific temperatures, were highly conducive to carburetor icing.
- The pilot was performing the descent with reduced engine RPM and without the carburetor heat turned on, which increased the risk of icing.
- The right-hand turn was initiated at an indicated airspeed very close to the aircraft's stall speed for the clean configuration.
- The engine failure was triggered by a momentary throttle adjustment that caused the engine to stumble in the presence of existing carburetor ice.
- The passenger's physical reaction to the sudden movement caused an unintended obstruction of the flight controls.
- The aircraft's center of gravity was positioned near the rear limit of the allowable range.