NTSB Factual Report

HISTORY OF FLIGHT

On July 1, 2017, about 0730 Pacific daylight time, a North Wing Scout XC light sport weight-shift-control (WSC) aircraft, N492XB, was destroyed when it impacted mountainous terrain while maneuvering near Chelan, Washington. The flight instructor and student pilot sustained fatal injuries. The aircraft was owned by the flight instructor who was operating it under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed for the local flight, which originated from Lake Chelan Airport (S10), Chelan, Washington, about 0630.

A review of video obtained from an onboard camera revealed that, earlier that morning, the student pilot completed a checkride to obtain a sport pilot certificate. The instructor informed the student pilot that he completed the checkride successfully. They subsequently departed again and continued to fly in the local area. Video showed that the pilots stayed in the traffic pattern before departing to the east. As the aircraft continued to climb away from the airport, the pilots discussed finding an area with less turbulence. About 19 minutes after takeoff for the accident flight, the instructor took over the flight controls and began to demonstrate a spiral dive. As he entered the maneuver, the aircraft's bank angle increased, and the aircraft rotated nearly 360° with its nose pointing straight down. The video stopped recording upon impact.

PERSONNEL INFORMATION

The instructor, age 70, held a private pilot certificate with an airplane single-engine land rating and a flight instructor certificate for light sport aircraft. The pilot was issued a third-class Federal Aviation Administration (FAA) airman medical certificate on April 19, 2016, with a limitation that he must have available glasses for near vision. On the application for that medical certificate, the pilot reported 6,000 total hours of flight experience, of which 100 hours were in the previous six months. A review of the pilot's logbook revealed that he accumulated a total of 3,012.9 hours in the WSC trike category.

The student, age 48, held a student pilot certificate and was not required to possess an FAA airman medical certificate. The student's logbooks were not available for review, and his flight experience could not be determined.

AIRCRAFT INFORMATION

The aircraft was manufactured in 2014 and purchased by the instructor in May 2017. The aircraft's maintenance records were not located and its maintenance history could not be determined.

The aircraft was equipped with a Rotax 912 series, 80-horsepower reciprocating engine. The engine was situated behind the rear seat in a pusher-type arrangement. The engine was electronically controlled and drove a 3-blade composite propeller.

The primary pilot station was the front seat. The rear seat occupant has no access to instruments. Both front and rear seat occupants had access to the control bar. Evidence suggest that the pilot occupied the rear seat and the student the front seat.

METEOROLOGICAL INFORMATION

The 0655 automated observation at Pangborn Memorial Airport (EAT), Wenatchee, Washington, about 35 miles southwest of the accident site, included wind from 310° at 11 knots, 10 miles visibility, temperature 24°C, dew point 9°C, and an altimeter setting of 29.91 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

The aircraft impacted terrain near the top of a hill in mountainous, rocky terrain and was destroyed by impact forces. The wreckage debris path was oriented on a heading about 130° magnetic. The first identified point of contact (FIPC) was a rock about 25 ft below the summit of the hill. The FIPC was characterized by an area of disturbed dirt surrounded by debris, including the front steering fork and the brake reservoir. A portion of the canopy was located left of the FPIC. The main wreckage, including most of the airframe, the engine, the wing, main landing gear, and propeller, was located about 50 ft from the FIPC on a heading of 320°, indicating that, following the impact, it rolled down the hill. One propeller blade was fractured and located about 30 ft north of the main wreckage. The rear seat was located within the main wreckage; the front seat was located along the debris path. Multiple separations throughout the flight control system were observed. All fracture surfaces were consistent with overload.

The engine cylinders, crankcase and overhead components were intact and displayed no evidence of catastrophic failure. Disassembly and examination of the engine revealed no evidence of abnormal wear or failure of internal components. Negligible impact damage was noted to the crankcase, reduction gear case, cylinders, and accessory section. Rocker arm, valve train, and accessory gear continuity was established by rotating the engine crankshaft by hand. All four cylinders developed pressure when the crankshaft was rotated. Internal examination of the pistons and cylinders using a lighted borescope revealed no anomalies. The piston faces and cylinder bores were clear and undamaged. The spark plugs were removed and displayed normal wear signatures. Impact damage was noted to both carburetors and the ignition system. Examination of the engine revealed no evidence of a preimpact mechanical malfunction or failure.

MEDICAL AND PATHOLOGICAL INFORMATION

The King County Medical Examiner, Seattle, Washington, performed an autopsy of the flight instructor and the student pilot. The cause of death for both individuals was listed as multiple blunt force injuries.

The FAA Bioaeronatical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology on specimens from the instructor and the student pilot. Testing of specimens from the instructor detected ethanol in muscle and brain, propanol in muscle, and atorvastatin in liver. Ethanol is the intoxicant commonly found in beer, wine, and liquor. Ethanol may also be produced in body tissues by microbial activity after death. Atorvastatin (often called Lipitor) is a cholesterol-lowering agent. The drug is not considered impairing. The tests for cyanide and carbon monoxide were not performed. Testing of specimens of the student pilot detected ethanol in muscle but not in liver; no drugs were detected in muscle. The tests for cyanide and carbon monoxide were not performed.

ADDITIONAL INFORMATION

Recovery from a Steep-banked Spiral Dive

According to the Weight-Shift Control Aircraft Flying Handbook (FAA-H-8083-5) Addendum, the purpose of practicing a steep spiral dive is to "build recognition of and a reflexive response to a steep-banked spiraling dive. Start all practice at an altitude that will permit a recovery at no lower than 1,000 feet above the ground (AGL). An altitude of at least 2,500 AGL is recommended…The pilot must be careful not to stall the aircraft or exceed airspeed limitations at all times."

NTSB Probable Cause

The flight instructor's failure to maintain control of the aircraft while demonstrating a spiral dive, which resulted in a loss of control. Contributing to the accident was the instructor's decision to demonstrate a spiral dive maneuver at an altitude that was too low for recovery.