NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The two commercially certificated flying pilots, accompanied by an airline transport rated pilot and a second passenger, departed Oakland, California, en route to North Bend, Oregon. A weather briefing had been obtained indicating an AIRMET for rime icing from the freezing level to 18,000 feet. The aircraft departed late in the afternoon, climbed to 12,000 feet and occasionally climbed to 13,000 feet for short durations in order to remain VMC above a cloud layer. Night environmental conditions existed when both engines began losing power and the copilot radioed Seattle Center that the aircraft had encountered "way too much induction ice to the engines," declaring an emergency. The pilot-in-command reported the outside air temperature at the power loss was about -20 degrees Celsius and he immediately applied full carburetor heat and began trouble shooting the problem while descending back toward a nearby airport. Application of carburetor heat bypassed the ice blocked induction air filters allowing unfiltered, warmed air to flow directly to the carburetors. Remedial action by the crew failed to regain full power and the aircraft broke out of the cloud bases in heavy snow too far down the runway to effect a landing. The pilot then began a turn to line up and land on the adjacent highway just east of the runway during which the aircraft's right wing struck several trees and the aircraft impacted near the west edge of the highway a short distance beyond.