St. George, UT, USA
N866P
BEECH 35-C33
The pilot reported that, while in cruise flight, the engine’s exhaust gas temperature was hotter than normal and that the fuel flow was lower than normal. Suddenly, all engine power was lost and despite multiple attempts, he was unable to restart the engine. During the subsequent forced landing, the pilot landed the airplane gear up on a road. Postaccident examination of the engine revealed that the mixture control arm was loose on the control shaft and the nut that secured the control arm to the shaft was loose. The mixture control arm machined chamfer had formed splines and exhibited deformation and movement of material. The nut and control arm mating surfaces showed corresponding rub marks. It is likely that the loose mixture control arm and the vibration of the engine allowed for the mixture control shaft to rotate to an idle cut-off position, thus resulting in the loss of engine power. No evidence of any additional mechanical malfunctions was found during the engine examination.
On March 21, 2012, about 0930 mountain daylight time, a Beech 35-C33, N866P, sustained substantial damage during a forced landing near St. George, Utah. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot and his passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the personal cross-country flight which originated from St. George about 0905 with an intended destination of Phoenix, Arizona. In a written statement to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that while in cruise flight at about 9,500 feet mean sea level (about 4,500 feet above ground level), the engine’s exhaust gas temperature was hotter than normal, and the fuel flow was lower than normal. Suddenly, all engine power was lost. The pilot stated that he attempted to restart the engine, but he was not successful. During the subsequent forced landing, the pilot landed the airplane gear up on a road. Postaccident examination of the airplane revealed that the firewall and a bulkhead were bent. The airplane was recovered to a secure location for further examination. Examination of the engine by a representative from Continental Motors Inc. and a Federal Aviation Administration (FAA) inspector under the supervision of the NTSB IIC revealed that the fuel metering unit was undamaged. The throttle control arm moved freely by hand. The mixture control arm moved freely by hand with no associated movement of the fuel control shaft and nut. The mixture control cable was removed and the mixture control arm was found loose on the control shaft. A recordable digital torque wrench was used to record the back-off torque from the nut. The recordable torque wrench records from 24 to 240 inch/lbs. There was no indication of torque found on the nut. The mixture control arm was removed from the shaft. The control arm machined chamfer had formed splines and exhibited deformation and movement of material. The nut and control arm mating surfaces showed rub marks. No evidence of any additional mechanical malfunctions was found during the engine examination. Review of the airplane logbook maintenance records revealed that the airframe and engine underwent the most recent annual/100-hour inspection on October 19, 2011, at an airframe total time of 5,840 hours and engine time since major overhaul of 1,165 hours. The pilot reported he had flown the airplane about 22 hours since the annual inspection.
The total loss of engine power due to the loose mixture control arm.
Source: NTSB Aviation Accident Database
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