Hays, KS, USA
N3631Z
Grumman G164
The pilot was performing an agricultural application flight, and the airplane was observed departing a private airstrip to the east toward a field west of the airstrip. The airplane impacted terrain in a steep, nose-down attitude. A postimpact fire ensued. There were no witnesses to the accident. Impact signatures and twisting of the wreckage were indicative of a nose-low spin, consistent with an aerodynamic stall . Flight control continuity could not be verified due to fire damage, but no anomalies were noted with the airframe and engine that would have precluded normal operation. The pilot's toxicology tests results showed no drug or alcohol use. Thus, it is likely that aerodynamic stall resulted from the pilot allowing the airplane to exceed its critical angle of attack during a turn.
HISTORY OF FLIGHT On August 20, 2019, at 0915 central daylight time, a Grumman-Schweizer G164-B airplane, N3631Z, impacted terrain near Hays, Kansas. The commercial pilot was fatally injured, and the airplane was destroyed by impact forces and postimpact fire. The airplane was owned and operated by Werth Aerial Spraying Inc. as a Title 14 Code of Federal Regulations Part 137 agricultural application flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight, which originated from the operator's private airstrip. According to a family member, the purpose of the flight was to apply chemicals to a neighbor's field west of the pilot's private airstrip. The family member observed the airplane departing the airstrip to the east and then turned away from the airplane. She did not see the airplane after it departed or for the remainder of the flight. The airplane impacted terrain 0.7 mile northeast of the airstrip. There were no witnesses to the accident. WRECKAGE AND IMPACT INFORMATION The airplane impacted a gravel road that was oriented east to west and an adjacent ditch. All wreckage was located within about 50 ft of the initial impact point, and ground scars were oriented on a 292° heading. The wings were oriented along an east-west direction, and the top of the wings faced south. The metal tube frame of the fuselage and empennage were oriented toward the north-northwest with the vertical and horizontal stabilizers rotated to the west. The engine was separated from the fuselage and located abeam the tail. The airplane's attitude at impact and impact angle could not be determined from the available evidence, but the damage to the wreckage and the orientation of the wreckage in relation to the initial impact point were consistent with an impact at a steep angle. A post-impact fire consumed most of the fuselage, cockpit, and inboard sections of the left and right wings. Flight control continuity was established from the ailerons, rudder, and elevators to the cockpit. Control continuity could not be established within the cockpit due to fire damage to the flight controls. The engine had separated from the main wreckage The propeller and throttle control levers were found in the full forward position. The mixture control lever was found near the full aft position. Engine control cables were continuous from their respective control levers to the engine firewall. The control cables terminated forward of the engine firewall in a manner consistent with overload. A teardown of the engine was performed, and no anomalies were found that could have led to a loss of engine power. The propeller spinner was removed, and both propeller blades were found to be in a low pitch position. One blade was bent aft about 90° near the midpoint of the blade. Gouges were present on the leading edge of the blade. The other blade was straight and exhibited leading edge gouging and polishing and chordwise scratches. Examination of the airframe and engine revealed no anomalies that would have precluded normal operation. MEDICAL AND PATHOLOGICAL INFORMATION The District Coroner, 23rd Judicial District of Kansas, performed an autopsy on the pilot. His cause of death was thermal injuries and carbon monoxide inhalation. Toxicology testing performed at the Federal Aviation Administration Forensic Sciences Laboratory was negative for ethanol, carbon monoxide, and all tested drugs.
The pilot's exceedance of the airplane's critical angle of attack, which resulted in an aerodynamic stall.
Source: NTSB Aviation Accident Database
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