DEN06LA094

Prior to departure, the airplane had been refueled with 37.5 gallons of 100 low lead fuel. Shortly after takeoff from runway 23, the pilot "heard a pop/bang from the engine...engine seemed to lose power." The pilot stated that he felt a "severe vibration" after the pop/bang engine noise. The pilot executed a 180-degree left turn in an attempt to return to the airport. Subsequently, the airplane landed in a grass field, impacted a dirt embankment and a fence, and came to rest upright in a ditch. Examination of the aircraft revealed that the throttle cable was routed above the rear mounted alternator belt, and the cable was resting on the alternator belt. The throttle cable shielding was worn through by contact with the alternator belt, and the braided cable was exposed. No damage was noted to the braided throttle cable. One of the tubes of the engine mounting frame was fractured; the fracture surfaces were consistent with an overload failure. Mechanical continuity throughout the engine was established when the propeller was rotated by hand, and the engine was test run on the airframe. The engine test run was performed for approximately 1 minute at an engine tachometer speed of 1,300 RPM. No anomalies were noted with the engine during the examination and test run. The reason for the partial loss of engine power could not be determined. A review of the airplane's logbooks revealed the airplane underwent annual and 100-hour inspections between the time the overhauled engine was installed on the airframe and the accident.

On June 30, 2006, at 1509 mountain daylight time, a Cessna 180 single-engine airplane, N153M, sustained substantial damage when it impacted terrain following a partial loss of engine power during initial takeoff climb from the Sheridan County Airport, Sheridan, Wyoming. The private pilot sustained minor injuries and the passenger sustained serious injuries. The airplane was registered to and operated by the pilot. Visual meteorological conditions prevailed, and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 91 personal flight. The flight was originating at the time of the accident.

According to the pilot, prior to departure, the airplane had been refueled with 37.5 gallons of 100 low lead fuel. Shortly after takeoff from runway 23, the pilot "heard a pop/bang from the engine...engine seemed to lose power." The pilot stated he felt a "severe vibration" after the pop/bang engine noise. The pilot executed a 180-degree left turn in an attempt to return to the airport. Subsequently, the airplane landed in a grass field, impacted a dirt embankment and a fence, and came to rest upright in a ditch.

Examination of the airplane by airport personnel revealed both wing struts were separated, both wings were bent, and the lower fuselage was crushed upward. A fuel sample was obtained from the left and right wing fuel tanks. The fuel samples were clear of contaminants.

A review of the airframe logbook revealed the airframe underwent its most recent annual inspection on November 21, 2005, at a total airframe time of 4,572.7 hours, and a tachometer time of 580.5 hours. A review of the engine logbook revealed that the Continental O-470K engine, serial number 47442-6-K, was overhauled in accordance with Teledyne Continental Motors (TCM) overhaul manual and installed on the airframe on July 24, 2004, at a tachometer time of 468.3 hours. The engine underwent its most recent 100-hour inspection on November 21, 2005. The tachometer time was 612.8 hours at the time of the accident.

On August 15, 2006, at the facilities of Beegles Aircraft Services, Greeley, Colorado, under the supervision of the NTSB investigator-in-charge, the airframe and engine were examined. Examination of the aircraft revealed that the throttle cable was routed above the rear mounted alternator belt, and the cable was resting on the alternator belt. The throttle cable shielding was worn through by contact with the alternator belt, and the braided cable was exposed. No damage was noted to the braided throttle cable. One of the tubes of the engine mounting frame was fractured; the fracture surfaces were consistent with an overload failure. Mechanical continuity throughout the engine was established when the propeller was rotated by hand, and the engine was test run on the airframe. The engine test run was performed for approximately 1 minute at an engine tachometer speed of 1,300 RPM. No anomalies were noted with the engine during the examination and test run.