NTSB Factual Report

HISTORY OF FLIGHT

On September 25, 2015, about 1126 mountain daylight time, a Beech S35 single-engine airplane, N193Q, impacted terrain following a loss of engine power while maneuvering near Pagosa Springs, Colorado. The private pilot and passenger sustained fatal injuries. The airplane was destroyed by the impact and postaccident fire. The airplane was registered to and operated by a private individual as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The airplane departed the Durango-La Plata County Airport (DRO), Durango, Colorado, at an unknown time, and was enroute to the Stevens Field Airport (PSO), Pagosa Springs, Colorado.

The accident airplane departed DRO with another airplane, and the two pilots planned to participate in an air race competition in the Pagosa Springs area on September 26th. Prior to landing at PSO, the pilots in the two airplanes, who were communicating via airplane radio, decided to execute a circuit in the Pagosa Springs air race course. As the airplanes entered the course, the accident airplane was behind the other airplane. After the first course waypoint, the accident pilot radioed the other pilot and stated the engine lost power, and the airplane was going down. No further communications were heard from the accident airplane.

Witnesses, who were located in the Pagosa Springs area, reported observing white smoke coming from the underside of the accident airplane. The airplane turned left, descended below rising terrain, and a smoke plume was then seen shortly thereafter. Witnesses stated the sky was clear and the winds were calm.

PERSONNEL INFORMATION

The pilot, age 70, held a private pilot certificate, with airplane single-engine land, airplane multi-engine land, and rotorcraft - helicopter ratings. In addition, the pilot held an airframe and powerplant mechanic's certificate. The pilot's most recent Federal Aviation Administration (FAA) third-class medical certificate was issued on August 19, 2014, with a limitation of "Must have available glasses for near vision."

According to the pilot's FAA medical certificate application, he reported a total of 5,640 flight hours and 20 hours in the previous six months. The pilot's logbook was not located during the investigation.

AIRCRAFT INFORMATION

The accident airplane was a 1964 Beech S35, serial number D-7708. The airplane was powered by a Continental Motors IO-520-B reciprocating engine and a Hartzell controllable pitch propeller. The airplane was issued a standard airworthiness certificate on December 7, 1964.

The maintenance logbooks were not located during the investigation. The total airframe and engine time could not be determined. According to a family member, the airplane underwent its most recent annual inspection in November 2014. The family member reported that approximately 2 or 3 years prior, the engine cylinders had been chromed. The family member was not aware of any additional maintenance on the airplane.

The following information was noted on the engine oil filter: Date: June 9, 2015; Tach Time: 2037.3.

METEOROLOGICAL INFORMATION

At 1153, the DRO automated surface observing system, located approximately 45 miles west of the accident site, reported the wind calm, visibility 10 miles, sky clear, temperature 21 degrees Celsius, dew point 4 degrees Celsius, and an altimeter setting of 30.44 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

Examination of the accident site revealed the airplane impacted a 4-inch steel pole adjacent to a gravel road. The steel pole displayed white paint transfer, and paint chips were found near the pole. The airplane then traveled about 200 yards before coming to rest inverted in a field. The main wreckage consisted of the fuselage, both wings, and empennage. The engine separated from the airframe and came to rest within the debris field. The three-blade propeller assembly separated from the engine and came to rest approximately 75 feet from the main wreckage. The fuselage and cockpit were consumed by postaccident fire.

The left wing came to rest inverted and partially attached to the fuselage. The flap was attached and found in the extended position. The aileron remained attached to the wing. The left main landing gear was found retracted and the gear door was closed. During recovery of the airplane, approximately 25 to 30 gallons of fuel was drained from the left wing tank.

The right wing came to rest inverted and partially attached to the fuselage. The flap was attached and found in the extended position. The aileron remained attached to the wing, and the outboard section displayed thermal damage. The right main landing gear was found retracted and displayed thermal damage. The right wing fuel tank was consumed by fire.

The fuselage, cockpit, instrument panel, and cockpit controls were consumed by fire. Three seat frames were located within the fuselage area. One seat belt buckle/tag and shoulder harness bayonet fitting were identified. The seat belt buckle and tag were clasped, and the shoulder harness bayonet was not engaged in the clasped buckle. The main cabin door latch bolt was retracted and the upper latch bolt hook was not extended. The position of the latch bolt and bolt hook were consistent with the door in an unlocked position.

The empennage was partially consumed by fire. The right stabilizer was bent upward, and the elevator remained partially attached to the stabilizer. The elevator was fractured mid-span. The left stabilizer displayed thermal damage, and the elevator remained attached.

Flight control continuity was established from the cockpit to the respective flight control surfaces. The down elevator flight control cable arm was separated from the pitch idler bellcrank in the empennage. The pitch trim actuator was extended 15/16 inches, which corresponded to a trim tab setting of 0 to 5 degrees trailing edge up. The right flap actuator nut was consumed by fire. The left flap actuator was extended 6 1/4 inches, which corresponded to a flaps down (30 degrees) position.

The engine separated from the engine mount. The upper engine cowling was separated from the fuselage and came to rest near the engine. The left interior cowling door and exterior cowling doors were coated with oil. Oil streaking was noted in a forward to aft direction.

The propeller assembly separated near the crankshaft propeller flange. The propeller blades remained attached to the propeller hub. One propeller blade was bent aft about mid-span, and two propeller blades were curled aft. Scratches were noted along the length of the propeller blades, and no leading edge damage was found on the blades.

MEDICAL AND PATHOLOGICAL INFORMATION

Autopsies were performed on the pilot and passenger by the Rocky Mountain Forensic Services, PLLC, Loma, Colorado. The immediate causes of death were listed as smoke and soot inhalation as a result of an accident.

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing on the pilot. The pilot's toxicological tests were positive for the following: 25 percent carbon monoxide detected in blood (heart), 0.7 ug/ml cyanide detected in blood (heart), Azacyclonol detected in urine, Fexofenadine detected in urine, and Ibuprofen detected in urine.

Hydrogen cyanide, otherwise known as cyanide, can be produced in high concentrations from the burning of nitrogen containing polymers. Cyanide is a highly toxic poison. Likewise, carbon monoxide is produced by the incomplete burning of various substances. Fexofenadine, commonly known as Allegra, is a non-sedating antihistamine used to relieve the allergy symptoms of seasonal allergic rhinitis (hay fever). Azacyclonol is a metabolite of fexofenadine. Ibuprofen, commonly known as Advil, Motrin, and others, is available as over-the-counter (OTC) or prescription strength. OTC ibuprofen is used to reduce fever and to relieve minor aches and pain from headaches, muscle aches, arthritis, the common cold, etc.

TESTS AND RESEARCH

On January 20, 2016, at the facilities of Continental Motors, Inc., Mobile, Alabama, the engine was examined under the supervision of the NTSB. Visual examination of the engine showed a hole in the engine crankcase above the No. 6 cylinder. The engine was disassembled for further investigation.

Disassembly of the engine revealed the Nos. 5 and 6 connecting rods were fractured and separated from the engine crankshaft. Debris, consistent with connecting rod and bearing material, was located in the engine oil sump. The No. 5 connecting rod crankshaft journal appeared to be undamaged. The No. 6 connecting rod crankshaft journal displayed thermal damage and rolled metal, which covered/blocked the oil transfer passage. The crankcase thru-bolts torque was measured, and the torque was found less than Continental Motors specified torque requirements. The No. 4 main bearing supports showed evidence consistent with fretting. The No. 4 main bearing journal displayed evidence of bearing shift and movement within the journal area consistent with the main bearing partially blocking or blocking the oil transfer passage to the No. 6 connecting rod. The No. 4 main bearing showed signatures of deterioration and delamination.

The engine pistons were removed and examined. The piston castings showed the following "NFS-C 550" casted on the inside of the piston head, and "C-510" etched near the piston pin. An internet search of NFS revealed the pistons were manufactured by Need For Speed (NFS) Pistons. According to the manufacturer website, the pistons are "Not Approved For Certified Aircraft Use", and are for "Experimental Aircraft and Airboat Use Only." According to the NFS company, the pistons were shipped to the pilot on February 2, 2011.

NTSB Probable Cause

Improper engine assembly by unknown maintenance personnel, which resulted in the failure of the No. 6 connecting rod due to oil starvation from the shifting of the crankshaft's No. 4 main bearing.