Beech V35A N35SD accident near Woody, California

Probable cause

An in-flight encounter with icing conditions during descent, which resulted in the airplane exceeding its critical angle-of-attack and experiencing an aerodynamic stall followed by an in-flight breakup.

NTSB analysis

During a visual flight rules cross-country flight, air traffic control was providing flight-following services. The pilot informed the controller that there was cloud cover ahead and requested an instrument flight rules clearance and approach to the destination airport. The controller granted the clearance and then instructed the pilot to maintain 14,000 ft; the pilot read back the clearance. The pilot then requested a lower altitude and was advised to expect a lower altitude in 10 to 12 miles. The pilot was subsequently cleared for a descent to 7,000 ft and issued arrival instructions. Two minutes later, the controller advised the accident pilot of a pilot report of icing in the area. One minute later, the controller issued a clearance to 6,000 ft but received no response from the pilot. The controller issued the clearance again, and the pilot acknowledged the instruction. The controller relayed a nearby outside air temperature but received no response from the pilot. The controller made several attempts to contact the pilot and also asked another pilot to try to establish contact; all attempts were unsuccessful. Two minutes later, radar contact was lost. The wreckage was located about 1 mile from the last radar return and was distributed over the terrain for about 1/2 mile, indicating that an in-flight breakup had occurred. A postaccident examination of the airframe or engine revealed no anomalies that would have precluded normal operation.

A weather study indicated that the airplane likely encountered light-to-moderate precipitation, especially near the end of the radar flight track. Precipitation and clouds would have reduced visibility. Considering the environmental freezing level, the airplane likely encountered supercooled liquid water and snowflakes about the time that voice communication was lost. Pilot reports in the immediate area described increasing instrument meteorological conditions (IMC) along with light-to-moderate icing conditions. The reports described the flight conditions as mostly smooth with some light turbulence when passing in and out of cloud tops. Along with the likely IMC, the airplane likely experienced moderate or greater icing conditions around the accident time. The airplane likely developed ice on the wings, which resulted in an aerodynamic stall followed by a loss of control and in-flight breakup during the descent.

Text from the NTSB. Open the NTSB docket for WPR13FA086 for the full record.