What happened
While operating on a VFR flight plan, the pilot contacted Seattle ARTCC to obtain an IFR clearance. After being cleared to climb to 15,000' MSL, air traffic control temporarily lost radar contact with the aircraft. The pilot was instructed to report upon reaching 15,000', which he did at 1329 PDT.
Approximately one minute after that report, the pilot notified controllers that he had lost "gyro suction" and would be flying using partial panel instruments. He also reported encountering light rime icing conditions and noted that he was flying in and out of clouds. Shortly after this communication, ARTCC lost both radio and radar contact with the aircraft. A witness at the scene reported hearing the sound of the engine revving immediately before the crash.
The investigation
An examination of the wreckage determined that the wings and empennage had separated from the aircraft during flight. Evidence indicated that the wings had failed downward. Additionally, the fuselage skin forward of the empennage showed signs of being ripped and torn, with numerous rivets pulled through the seams.
Investigators performed a check of the vacuum pump, which revealed evidence of seizure resulting from long-term engine oil contamination and wear.