What happened
During an IFR arrival at night, the pilot was cleared for a VOR/DME-A approach. Although the aircraft was not equipped with DME, the pilot was cleared to descend and maintain 4200' MSL until reaching the VOR. Upon reaching the VOR, the pilot began a procedure turn to intercept the inbound course of 105 degrees. During this maneuver, the aircraft began losing altitude. Despite applying full power, the pilot was unable to maintain the required altitude.
Radar data indicated that after initiating the procedure turn, the aircraft crossed the inbound radial while heading east and continued for 13 miles. The pilot then turned south to intercept the inbound course, but the descent continued. The aircraft crashed on a rising mountain slope approximately 15 miles northwest of the airport at an altitude of about 2300' MSL, which was below the minimum descent altitude of 2360'. There were no fatalities reported.
The investigation
The investigation found no preimpact mechanical problems. Environmental conditions at the time included a surface temperature of 43 degrees and a dew point of 40 degrees, conditions highly conducive to carburetor ice formation. A passenger reported that the flight encountered severe carburetor icing and possible en route structural ice. To manage the situation, the pilot cycled the carburetor heat on and off to burn off the ice and used the airspeed indicator as an indicator for ice accumulation.