NTSB Factual Report

HISTORY OF FLIGHT

On July 27, 2015, about 1724 central daylight time, a Beech M35 airplane, N9CB, was destroyed after impacting terrain near Amery, Wisconsin. The pilot and three passengers were fatally injured. The airplane was registered to and operated by St. Croix Bonanza Association LLC under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The flight departed from New Richmond Regional Airport (RNH), New Richmond, Wisconsin about 1716 and was destined for Voyager Village Airstrip (9WN2), Webster, Wisconsin.

The co-owner of N9CB witnessed the airplane depart from Runway 14 at RNH. He estimated the airplane became airborne about 1,700 feet down the runway, versus a typical ground run of about 1,000 feet. He was concerned for weight and balance reasons when he saw there were four persons in the airplane.

A review of air traffic control radar revealed returns (primary radar only) coincident with the departure time and direction of the planned flight for N9CB. The returns indicated the airplane proceeded from RNH on a northeast track for 7 miles, followed by a right turn near the accident site. Altitude information was not available, due to line of sight limitations of the radar site.

Several witnesses located near the accident site noticed the airplane maneuvering immediately prior to the accident. One witness described the airplane in a steep climb, followed by "making a circle and then twisting" just prior to disappearing behind a tree line. Another witness reported seeing the airplane in a nose down attitude with its wings rocking. Three other witnesses noticed the airplane in a spiraling descent prior to impact and stated the airplane had previously been performing aerobatics, "tricks", or "stunts".

PERSONNEL INFORMATION

The pilot, age 44, held a private pilot certificate with an airplane single engine land rating, as well as a mechanic airframe and powerplant certificate. On May 15, 2015, the pilot was issued a Class 3 medical certificate, with no restrictions. A review of the pilot's flight records indicated that he had logged a total of 368.6 flight hours. During the 90 days prior to the accident, the pilot had flown 6 flights in the accident airplane, with an estimated duration of 13 flight hours.

AIRCRAFT INFORMATION

The airplane, N9CB (s/n D-6231), was a Beechcraft M35 Bonanza manufactured in 1959. The airplane was equipped with a Continental Motors IO-470-C engine (s/n 71133-7-C), a 2-blade, all-metal, constant speed propeller, two 25-gallon main fuel tanks, two 10-gallon auxiliary fuel tanks, and two 15-gallon tip tanks.

On February 7, 2015, the airplane underwent an annual inspection, at an airframe total time of 6,244 hours and a tachometer time of 4,209 hours. The engine was last overhauled on September 26, 2014, at a tachometer time of 4,150 hours.

WEATHER INFORMATION

At 1715, the weather observation station at RNH, located about 7 miles southwest of the accident site, reported the following conditions: wind 150 degrees at 9 knots, 10 miles visibility, scattered clouds at 3,100 feet above ground level, temperature 29 degrees C, dew point 20 degrees C, altimeter setting 29.94 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

The airplane impacted into an open wheat field. Impact signatures were consistent with a 10 to 15 degree nose down attitude and a low forward velocity. A post-crash fire ensued and consumed the cabin area into the rear fuselage area, as well as outboard on the wings, into the wheel well and auxiliary tank area.

The airplane was found intact lying upright on the ground, with the wing leading edges compressed inward on their lower side and ballooned upward on their upper side. The right wing leading edge was separated on the top side from the forward spar.

The landing gear and flaps were retracted, with the landing gear and flap actuators in the up position. The trim tab trailing edge was aligned with the trailing edge of the elevator.

The fuel selector valve was found trapped under the forward wing carry though structure. The fuel selector valve placard was folded around the selector valve handle. The selector valve stem was bent. The fuel selector was in the off position, which was consistent with structure deformation in the area of the selector. The fuel lines and tanks were consumed by fire.

No anomalies were noted with the flight control system. All flight control cables from the cockpit (pitch, roll, and yaw) remained attached to their respective cockpit control and all of the flight control cables were attached to their respective bellcranks near the flight control surfaces. The flight control surfaces remained attached to their respective airframe surfaces. The airplane was equipped with a single throw-over yoke, which was positioned on the left side.

The engine was separated from the aircraft. A postaccident examination of the engine revealed the propeller was separated from the engine and remained attached to the crankshaft propeller flange. The crankshaft was fractured where it entered the crankcase and the fracture surface displayed 45-degree shear lips and cupping. The engine sustained thermal damage that partially melted the housing of a number of the components. The engine sustained impact-related damage that deformed the camshaft drive gear and front crankcase, which precluded rotation of the crankshaft.

The top Champion RHM38E sparkplugs were removed from the cylinders. All displayed a normal worn condition when compared to the Champion Aviation Service Manual (AV6-R). None of the sparkplugs were fouled. The fuel injector lines were removed from the nozzles and each of the nozzles was removed from its respective cylinder. No obstructions were noted in any of the nozzles.

All six cylinders remained attached to the crankcase. The rocker covers were removed and no pre-accident anomalies were noted with the rockers, rocker shafts, or valve springs. A borescope inspection of the six cylinders was conducted, which revealed no anomalies with the piston, cylinder barrel, cylinder head, valve or valve seats.

The vacuum pump was separated from the backside of the engine and sustained impact and thermal damage. Disassembly of the vacuum pump revealed that the rotor was fractured, but all six of the pump vanes remained intact.

Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.

MEDICAL AND PATHOLOGICAL INFORMATION

On July 28, 2015, an autopsy was performed on the pilot by the Midwest Medical Examiner's Office in Ramsey, Minnesota. The cause of death was blunt force injuries. The FAA's Civil Aeromedical Institute in Oklahoma City, Oklahoma performed toxicology tests on the pilot. No tested for drugs were detected.

TESTS AND RESEARCH

An Appareo Stratus 2, which is a battery operated receiver with GPS capability, was recovered from the accident site and evaluated by the NTSB Recorder Laboratory. It was determined that the device did not store any flight data.

WEIGHT AND BALANCE

According to the co-owner of N9CB, the pilot's normal routine was to depart with the airplane's main/auxiliary tanks full. Following his flight on the day prior to the accident, fueling records indicated the pilot fueled the airplane with 23.9 gallons of fuel, which was consistent with filling the main/auxiliary tanks full. The weight of the airplane was estimated to be 3,145 pounds, based on full main/auxiliary fuel tanks and the driver's license weight of the pilot and passengers. The maximum takeoff weight for the airplane was 3,150 pounds.

This maximum takeoff weight was based on a Beryl D' Shannon Aviation Specialties tip tanks supplemental type certificate (STC), which approved an increase of the maximum takeoff weight by 200 pounds. The STC's airplane flight manual supplement does not provide guidance on degraded performance or change airspeed indicator markings to reflect the increase in maximum weight.

ADDITIONAL INFORMATION

A close friend of the pilot stated they had flown together four times in the accident airplane, during which the pilot enjoyed and frequently performed practice stalls. He stated the pilot flew at low altitude several times to "test the waters" and on one occasion, flew about 200 feet agl while "buzzing" a friend's house. This episode, as well as the pilot's frequent performance of practice stalls, concerned him enough that he did not want his son to fly with the accident pilot alone. He stated the pilot and all three passengers, whom he also knew very well, tended to "live life on the edge" and were not averse to high risk activities.

NTSB Probable Cause

The pilot’s loss of airplane control while maneuvering with the airplane near its maximum gross weight, which resulted in the airplane exceeding its critical angle-of-attack and entering an aerodynamic stall.