Accident Brief: Two Died In Kolb TWINSTAR Accident

The private pilot, who had recently purchased the experimental amateur-built light-sport airplane, and a passenger were conducting a local flight in day visual meteorological conditions. Witnesses stated that the airplane departed and remained in the airport traffic pattern. While the airplane was on approach to the runway for landing, witnesses heard the engine power decrease then and immediately increase. The airplane appeared to enter an aerodynamic stall from a low altitude and impact terrain in a nose-low attitude. Postaccident examination of the airplane revealed no evidence of mechanical malfunctions or failures that would have precluded normal operations. Based on available information and examination of the wreckage, it is likely that the pilot did not maintain sufficient airspeed while maneuvering during the approach for landing. The airplane subsequently exceeded its critical angle of attack and entered an aerodynamic stall at an altitude too low for recovery.

The pilot's logbook was not located during the investigation, and the pilot's experience level in experimental and light-sport airplanes was not determined. Additionally, it could not be determined if the pilot had obtained transition training in the accident airplane, which was classified as a low-inertia/high-drag airplane. Low-inertia/high drag airplanes are particularly susceptible to unintentional aerodynamic stalls due to their margin between low cruise speed and stall speed and their tendency to experience significant airspeed decay with increased load factor (such as during a turn).

Toxicology revealed that the pilot was using pain and allergy medications at the time of the accident; however, whether the pilot had impairing levels of either of the medications around the time of the accident or whether the potentially-impairing medications degraded his ability to safely operate the airplane could not be determined.

Probable cause(s): The pilot's failure to maintain airspeed during a visual approach for landing, which resulted in an exceedance of the airplane's critical angle of attack and a subsequent aerodynamic stall at an altitude too low for recovery.

NOTE: The report republished here is from the NTSB and is printed verbatim and in their complete form.

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Isabel GoyerWriter