History of Flight
On July 17, 2022, about 0938 mountain daylight time, a Cessna P337G, N337KN, was destroyed when it was involved in an accident near Gold Hill, Colorado. The pilot and three passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 air tour flight.
The owner of the company reported the accident flight was a local sightseeing flight, which was to remain within 25 nautical miles of the departure airport.
ADS-B data showed that the airplane departed from Rocky Mountain Metro Airport (BJC), Broomfield, Colorado, (elevation 5,674 ft msl) and proceeded along a westerly course for about 4 minutes before entering a right turn to a northwesterly heading. For the next 10 minutes and 40 seconds, the airplane maintained a ground speed between 90 and 105 knots while maintaining a climb rate of about 380 ft per minute.
After leveling off at an ADS-B reported pressure altitude of 9,500 ft, the airplane was traveling about 95 kts. It slowed to about 92 kts while maintaining altitude, and 20 seconds later, began a turn to the left. The airplane’s rate of descent increased, and the airplane descended 1,100 ft over the next 10 seconds; the last recorded data point was located at an altitude of 8,400 ft about 579 ft northeast of the accident site.
A witness near the accident site reported seeing the airplane descending as it neared his position. He said the airplane was very loud as if the engine was running at full power. The witness saw the airplane’s right wing rise abruptly before it entered a nose-down attitude and began to corkscrew until it descended out of view.
Another witness stated that the airplane was flying super low. She reported that the engine made a clickity-clackity-type of sound, like it was not running smooth. The right wing lifted, then quickly lowered, before the left wing lowered and the airplane entered a clockwise corkscrew descent before the tree line. When the left wing lifted, the engine noise stopped and she was certain that the engines sounded like they were struggling.
Personnel Information
The pilot was hired as a private contractor about 6 weeks before the accident. The accident flight was his fourth tour flight with the company. His logbooks were not located, but dispatch logs showed he had flown the accident airplane for a total of 3.5 hours, of which 1.1 hours were described as training. At his most recent FAA medical exam on February 17, 2022, he reported 550 total hours flight experience.
The owner of the company reported that the pilot’s training included 3 hours of ground instruction via video conference, followed by training in the airplane, which included showing the pilot the route of the tours and conducting some maneuvers. The training included several scenarios, including gear retraction failures, smoke in the cockpit, and pressurization issues. During the flight, the owner would usually shut an engine down; however, he decided to simulate a loss of engine power by reducing the rear engine to zero thrust. The owner said it was a short checkout, but he was extremely confident to sign the pilot off.
Aircraft Information
The operator, Bluebird Aviation, operated under a 91.147 letter of authorization issued by the FAA’s Denver Flight Standards District Office on January 6, 2022. The provisions allowed the operator to provide nonstop commercial air tours within a 25-statute-mile radius of the base airport.
According to the operator, the ADS-B-depicted route followed the general direction of a standard tour, and typically the maximum altitude attained during such a tour would be between 12,500 and 13,000 ft msl.
The airplane owner’s manual contained charts for two-engine climb performance and single-engine climb performance. The charts included sections for climb performance at 5,000 ft at 41°F and 10,000 ft at 23°F, with notes stating, “for hot weather, decrease rate of climb 40 ft./min for each 10° above standard day temperature for particular altitude” and “for hot weather, decrease rate of climb 25 ft./min for each 10° above standard day temperature for particular altitude,” respectively. Using the reported temperature at the departure airport and a maximum gross weight of 4,700 lbs, two-engine climb performance charts indicated a climb rate of 1,060 fpm at 5,000 ft, or 895 fpm at 10,000 ft. The single-engine climb performance chart indicated a 215-fpm climb rate at 5,000 ft, and a 95-fpm climb rate at 10,000 ft.
Meteorological Information
Using reported weather conditions, the calculated density altitude at the departure airport was 7,677 ft, with a pressure altitude of 5,012 ft.
Wreckage and Impact Information
The airplane impacted mountainous terrain on a heading of about 283° magnetic at an elevation of 7,789 ft msl. The first identified point of contact was a cluster of trees severed or broken about 20 ft above the ground. These trees were within an area of trees about 75 to 100 ft tall. The airplane came to rest mostly upright on a heading of about 019° magnetic. All major structural components were within about a 30 ft by 40 ft area. The area surrounding the wreckage was fire damaged.
The fuselage was mostly consumed by fire. A portion of the instrument panel was observed with various avionics separated and thermally damaged. The throttle quadrant was located and exhibited impact and thermal damage. Flight control continuity was established from the middle of the fuselage to all primary flight control surfaces. Multiple areas of separation in the control cables exhibited splayed signatures consistent with tension overload.
The front engine exhibited extensive thermal and impact damage. Visual mechanical continuity was established throughout the engine. The fuel pump was separated from its mounts. The throttle plate appeared to be in the full open position. The fuel pump would not rotate by hand and exhibited impact damage; disassembly found it unremarkable. The fuel manifold valve was thermally damaged; the diaphragm was thermally damaged, and the screen contained burnt debris.
The rear engine was separated from the engine mount. Visual mechanical continuity was established throughout the crankshaft, camshaft, and connecting rods. The throttle plate was observed in an almost-closed position. Cylinders Nos. 2, 4, and 6 were unremarkable except for corrosion throughout. The fuel pump was impact and thermally damaged; the drive shaft would not rotate by hand; disassembly revealed corrosion and thermal damage. The mixture control lever was separated. The fuel manifold valve exhibited thermal damage; the diaphragm was thermally damaged and unable to be removed.
The front propeller had chordwise scratches and S-bending. All six mounting holes were ovalized with internal threads ripped out. Witness marks from contact between the feathering spring and both blade root faces were observed, consistent with both blades in the normal operating range.
The rear propeller was mostly intact; about 8 inches of the tip of one blade was melted and missing. Oil was present in the actuating cylinder, and plastic ball bearing separators were melted and solidified inside the hub. The rear propeller’s blades were in the feathered position, with little scratching or bending.
Medical and Pathological Information
An autopsy of the pilot performed by Boulder County Coroner listed the cause of death as “blunt force injuries.” Toxicology testing found no drugs of abuse.