WPR14LA208

The commercial pilot reported that the airplane was in cruise flight at 12,500 ft mean sea level (msl) when he noticed a partial loss of engine power and that the No. 1 cylinder exhaust gas temperature had dropped from 1,450 to 1,300 degrees F. The pilot diverted to an airport about 10 miles away; however, the engine then experienced a total loss of power about 4,000 ft above ground level. The airplane was unable to reach the airport, so the pilot performed a forced landing on a dirt road, during which the firewall was substantially damaged and the right main landing gear collapsed. A postaccident engine test run at various power settings revealed no mechanical failures or malfunctions that would have precluded normal operation. Weather conditions at the time of the accident at the airplane's cruise altitude of 12,500 ft msl were conducive to the formation of carburetor icing at glide and cruise power. During the on-site examination of the wreckage, the carburetor heat control was found in the "off" position. It is likely that the engine lost power due to carburetor ice and that the timely application of carburetor heat would have restored engine power.

**This report was modified on November 2, 2016. Please see the docket for this accident to view the original report.** On May 24, 2014, at 1500 Pacific daylight time, a Cessna 182P airplane, N21048, experienced a total loss of engine power and executed a forced landing onto a dirt road on the south side of Mammoth Lakes, California. The airplane sustained substantial damage to the firewall during the landing sequence. The airplane was registered to, and operated by, the commercial pilot under the provisions of 14 Code of Federal Regulations, Part 91. The pilot and single passenger were not injured. Visual meteorological conditions prevailed for the flight and a visual flight rules flight plan was filed. The flight originated at Bishop, California. The pilot stated that while en route to Los Banos, California, on V230, 10 miles west of RBRTS intersection at a cruise altitude of 12,500 ft mean sea level he noticed a change in engine sound/cadence followed by the number 1 engine cylinder exhaust gas temperature (EGT) drop from a 1,450 to 1,300 degrees Fahrenheit, and the engine then experienced a complete loss of power at an approximate altitude of 4,000 ft above ground level. He informed air traffic control (ATC) and diverted southeast towards Yosemite Mammoth Airport, which was approximately 10 miles away. The pilot failed to reach the airport and landed on a dirt road on the south side of the town of Mammoth Lakes. During the landing the right main landing gear collapsed and the engine firewall was damaged. A review of weather conditions at the time of the accident indicated a temperature of 1 degree Celsius, dew point of minus 6 degrees Celsius, and a relative humidity of 60% at 12,500 which posed a potential for carburetor icing at glide and cruise power. During the on site examination of the wreckage the carburetor heat control was found in the off position During the postaccident examination of the airframe and engine, the engine was prepared for an engine run. The engine started and was run at various power setting for several minutes before it was shut down. No anomalies were revealed what would have precluded the engine from producing power.