History of Flight
On March 26, 2009, about 2030 central daylight time, a twin-engine Cessna 337 Skymaster, registration N373E, departed from a private airstrip located approximately 7 miles south of Stillwater, Oklahoma. The airplane was substantially damaged upon impact with terrain. The airline transport pilot, the sole occupant, was fatally injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight without a flight plan. Night visual meteorological conditions prevailed.
Several witnesses in the vicinity reported seeing or hearing the airplane depart the runway and circle the area before it impacted the ground. Witnesses stated that the airplane was flying low and that the engine or engines were running rough or misfiring. They added that the engines went silent before the airplane nosed sharply downward. Witnesses also reported that the pilot intended to fly to Stillwater Regional Airport to refuel.
Aircraft and Pilot Information
The airplane was a 1968 Cessna 337 Skymaster, a high-wing, all-metal, twin-engine aircraft with a push-pull configuration and retractable tricycle landing gear. It was powered by two Teledyne Continental Motors IO-360-C reciprocating engines, each rated at 210 horsepower. The last annual inspection was performed on May 22, 2008, at a total airframe time of 3,169.3 hours.
The pilot held an Airline Transport Pilot certificate for airplane single-engine and multi-engine land. A third-class Federal Aviation Administration medical certificate was issued in June 2007. The pilot's logbook indicated approximately 23,620 total flight hours.
Meteorological Information
At 2053, the automated weather observing system at Stillwater Regional Airport, approximately 10 miles north of the accident site, reported wind from 050 degrees at 10 knots, visibility 10 miles, clear sky, temperature 51°F, dew point 46°F, and an altimeter setting of 29.71 inches of mercury.
Communications
The pilot was not in communication with air traffic control at the time of the accident, and no distress calls were reported.
Wreckage and Impact Examination
The airplane came to rest in a steep nose-down, wings-level attitude. The front engine and cabin area were largely destroyed by the impact and mostly submerged in water. All major components of the airplane were accounted for at the accident site, which was a small ravine containing several large trees. Ground and impact signatures were consistent with the airplane being in a nose-low attitude at collision.
The left and right wings and tail booms remained attached to the fuselage. The main landing gear was extended, and the flaps were retracted. Tail surfaces exhibited only minor damage. Control continuity to the flight controls was established up to the front cabin area. The overhead fuel selector panel and control cables were broken or stretched, and the position of the fuel valves before impact could not be determined.
The left auxiliary and main wing fuel tanks contained approximately 3 gallons of fuel each. The right wing and auxiliary fuel tanks contained a total of about 1 gallon. The front fuel strainer/gascolator was found submerged and filled with water; the rear strainer/gascolator was empty.
Engine Examinations
On-site examination of the engines did not identify any pre-impact malfunctions. The rear engine was removed and shipped to a Teledyne Continental Motors test facility. On April 27–28, 2009, it was examined under supervision and placed in a test cell. After minor component replacements, the engine started and ran at various power settings without hesitation, producing rated horsepower.
The front engine was examined on May 7, 2009, at a salvage facility. The crankshaft propeller flange had separated from the crankshaft due to impact forces. The spark plugs appeared normal. The engine was rotated by hand, establishing continuity. Thumb compression and borescope inspections were conducted on each cylinder and revealed no abnormalities. The magnetos, which had been submerged, were dried and produced spark at all posts.
The front propeller remained attached to the engine; one blade showed a forward curve starting at mid-span, and the other had a gentle curve toward the non-cambered side near the root. The rear propeller remained attached and had contacted the engine cowling during the accident sequence, rotating less than one revolution. The rear propeller blades had no apparent damage.
Medical and Toxicological Information
An autopsy conducted by the Oklahoma Office of the Chief Medical Examiner determined the cause of death as chest trauma due to crushing blunt force. Toxicological testing performed by the FAA Toxicology Accident Research Library was negative for carbon monoxide, cyanide, ethanol, and drugs.