Background
The aircraft departed Oakland, California, en route to North Bend, Oregon. On board were two commercially certificated flying pilots, one airline transport rated pilot, and a second passenger. A weather briefing had been obtained that indicated an AIRMET for rime icing from the freezing level to 18,000 feet.
Flight Sequence
The departure occurred late in the afternoon. The aircraft climbed to 12,000 feet and occasionally climbed to 13,000 feet for short durations to remain in visual meteorological conditions (VMC) above a cloud layer. Night conditions were present when both engines began losing power. The copilot radioed Seattle Center, reporting that the aircraft had encountered "way too much induction ice to the engines" and declared an emergency.
Power Loss and Emergency Actions
The pilot-in-command reported that the outside air temperature at the time of power loss was about -20 degrees Celsius. He immediately applied full carburetor heat and began troubleshooting the problem while descending toward a nearby airport. The application of carburetor heat bypassed the ice-blocked induction air filters, allowing unfiltered, warmed air to flow directly to the carburetors. However, the crew's remedial actions failed to regain full power.
Landing Attempt and Accident
The aircraft broke out of the cloud bases in heavy snow, but was too far down the runway to effect a landing. The pilot then began a turn to line up and land on an adjacent highway just east of the runway. During the turn, the aircraft's right wing struck several trees, and the aircraft impacted the ground near the west edge of the highway a short distance beyond.