NTSB Factual Report

HISTORY OF FLIGHT

On September 2, 2016, about 1000 central daylight time, an experimental, amateur-built RV-6 airplane, N676DT, impacted a cornfield following a loss of control near Viborg, South Dakota. The commercial pilot and the passenger were fatally injured, and the airplane was destroyed. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan had been filed. The local flight departed from Marv Skie-Lincoln County Airport (Y14), Tea, South Dakota, about 0900.

Family members reported that the passenger was the pilot's 14-year-old granddaughter, who aspired to become a pilot, and that it was very common for them to take local flights on the weekends. They added that the purpose of the flight was personal and not instructional.

A witness reported hearing an engine "sputtering," followed by a loud "thud," and then he observed a fireball. The witness did not see the airplane in flight.

PERSONNEL INFORMATION

AIRCRAFT INFORMATION

The airplane was built from a kit by a previous owner, and it was configured for two occupants with side-by-side seating. The airplane received a special airworthiness certificate with an experimental designation on September 11, 1996.

The investigation was unable to determine when the airplane had been fueled last.

METEOROLOGICAL INFORMATION

There were no active AIRMETs or SIGMETs near the accident location. Also, there were no PIREPS applicable to the accident area.

WRECKAGE AND IMPACT INFORMATION

The accident site was located in a mature cornfield about 10 nautical miles west of Viborg and 27 nautical miles southwest of Y14. The airplane came to rest on top of the corn stalks, some of which remained unbroken near the empennage. The wreckage exhibited no lateral or forward displacement. Outside of the wreckage area there was no airplane debris and no noticeable damage to the crop. According to first responders, the passenger was seated in the left seat and her 4-point seatbelt remained fastened. The pilot was seated in the right seat and his 4-point seatbelt remained fastened.

The engine cowling, cockpit, fuselage, and forward portion of the empennage were consumed by a postimpact fire (figure 1).

The wing roots and bottom side of the fuselage were thermally damaged. The wing tank fuel caps were found in place and secure.

The left wing tip fairing separated from the wing and was found near the forward left side of the wreckage. The left wing exhibited rearward and upward impact crushing signatures (figure 2). Impact marks were found under the left wing tip. The left flap was partially underneath the left wing and remained attached at the connection points. The left aileron remained partially attached to the wing; the inboard connection remained attached while the outboard connection was impact separated. The left fuel tank was breached.

The right wing sustained leading edge damage and rearward crushing near the inboard section. The right flap was retracted and mostly undamaged. The right aileron was found in a neutral position, remained attached, and was mostly undamaged.

The aileron control tubes remained attached to the aileron surfaces and were continuous inboard to the fuselage where they were both consumed by fire.

The elevator control tube remained attached to the elevator surface and extended about 4 ft into the rear fuselage where it was thermally damaged and partially consumed by fire. The forward portion of the elevator control tube remained attached to its connection at the control stick. The elevator trim tab was slightly down from the neutral position. The rudder control cables remained attached to each side of the rudder. The rudder control cables were continuous to the forward ball swage in the cockpit area, and the right ball swage was covered with melted aluminum. The rudder pedals were found in the forward cockpit near the firewall and sustained thermal damage and impact damage.

The throttle and mixture control knobs were near the full forward position. The cockpit instrumentation was mostly consumed by fire. The ignition was positioned to "BOTH." The fuel selector was set to the right fuel tank position.

The two-bladed metal propeller remained attached to crankshaft flange. The propeller was embedded in the soil and positioned horizontally (figure 3). The propeller blades were slightly bent aft and did not exhibit any leading edge damage.

The engine remained attached to the engine mounts and sustained thermal damage primarily near the rear, which encompassed the engine accessories. The top spark plug electrodes, which were all automotive style plugs, were free of damage and exhibited coloration consistent with normal operation. The empennage and exhaust manifold did not contain any visible oil residue. Engine mechanical continuity was established from the vacuum pump drive to the propeller flange. When the crankshaft was rotated via the accessory drive gear, thumb compression and suction were obtained at each cylinder. The valve rockers were undamaged and exhibited movement consistent with normal operation. The magneto drive gear in the accessory section and fuel pump plunger actuated when the accessory drive gear was rotated. The engine driven fuel pump was thermally damaged. The carburetor remained secure on its mounting pad with the mixture and throttle controls secure at their respective connections. The carburetor throttle control was near the full open position, and the mixture was near the full rich position. The carburetor fuel inlet screen was free of contaminants. The carburetor air inlet was free of obstruction. The carburetor was removed and opened for examination, which revealed that the float bowl remained free of contamination and the plastic floats were thermally damaged. The left and right electronic ignition components were thermally damaged. The ignition harness was mostly consumed by fire; however, it appeared to have been connected at each spark plug. The vacuum pump remained secure to its mounting pad, and the plastic coupler was thermally damaged. The engine oil suction screen was free of contaminants.

The postaccident examination of the engine and airframe did not reveal any mechanical malfunctions or anomalies that would have precluded normal operation. The postimpact fire prevented a complete examination of the airplane.

MEDICAL AND PATHOLOGICAL INFORMATION

The Sanford Health Pathology Clinic, Sioux Falls, South Dakota, completed an autopsy on the pilot, and the cause of death was multiple blunt force injuries. The Federal Aviation Administration's (FAA) Bioaeronautical Sciences Research Laboratory conducted toxicology testing, which revealed verapamil and norverapamil in the blood and liver.

Verapamil is a prescription drug used in the treatment of hypertension, angina, and arrhythmias. Norverapamil is a metabolite of verapamil.

The Sanford Health Pathology Clinic also completed an autopsy on the passenger, and the cause of death was blunt force injury. The FAA's Bioaeronautical Sciences Research Laboratory conducted toxicology testing, which was negative for carbon monoxide in the blood.

ADDITIONAL INFORMATION

A review of FAA radar data for the accident area did not reveal any radar returns that correlated to the flight. Also, there were no air traffic control communications found from the airplane.

An undamaged Appareo Stratus PRX V2 was found near the wreckage. The unit was downloaded by the NTSB Recorders Laboratory and did not reveal any data from the accident flight.

The pilot's iPad was found by the family, and the ForeFlight application revealed 37 previous flight track logs. The track logs were from November 29, 2014 to July 26, 2016.

NTSB Probable Cause

The pilot's failure to maintain airplane control, which resulted in the airplane exceeding its critical angle of attack, an aerodynamic stall, and subsequent flat spin into terrain.