A Washington pilot who died in the crash of a Yute Air plane during a maintenance flight near Bethel last year had moderate levels of a toxic gas in his system, which National Transportation Safety Board investigators believe came from the aircraft's engine.
Olympia, Washington, resident Blaze Highlander, 47, died when the Cessna 207 he was flying crashed into the Kwethluk River on May 30. The plane, reported missing on a 3 1/2-hour flight out of Bethel that morning after recent engine maintenance, was found about 40 miles southeast the next day. Highlander, the pilot and sole occupant, was discovered dead in the wreckage by investigators.
The NTSB's June preliminary report on the crash found that GPS-based telemetry data being broadcast by the aircraft tracked it to an altitude of 475 feet before it struck a tree and plunged into the river. Clint Johnson, the NTSB's Alaska chief, said it was unlikely weather -- visibility was reportedly "unrestricted" in Bethel on the day of the crash -- would prove to be a factor in the crash.
An NTSB toxicology examination of Highlander's blood released Monday found a 21 percent saturation of carbon monoxide, a gas found in engine exhausts that can cause symptoms ranging from disorientation to death over time.
A fact sheet on carbon monoxide from the U.S. Centers for Disease Control and Prevention states that carbon monoxide saturation greater than 2 percent in nonsmokers or 9 percent in smokers "strongly supports a diagnosis of CO poisoning."
Millicent Hoidal, the NTSB investigator examining the Yute Air crash, said Tuesday the most likely source for the carbon monoxide in Highlander's system was the plane's Continental Motors IO-520 engine. Further details on how that happened are set to be released in a May factual report on the crash.
"What we know is that the carbon monoxide did come from the airplane," Hoidal said. "It wasn't something that he had before he got in the airplane."
Hoidal said that despite the toxicology findings, it's not clear how severely impaired by the gas Highlander may have been. She said typical blood saturation levels found in carbon monoxide poisonings range from 50 to 60 percent.
"CO affects different people in different ways," Hoidal said. "He may have been feeling the effects of it, but to what degree it's difficult to tell."
The Yute Air crash is one of several fatal 2015 events being covered this year by the Smithsonian Channel series "Alaska Aircrash Investigations," which has prompted the NTSB to release factual dockets of information on crashes ahead of the air dates for episodes involving them.
In addition to the toxicology report, the docket released for the Yute Air crash includes several photos of the wreckage and crash site, as well as a drawing of its engine exhaust system that includes a marked cabin heat outlet. A Continental Motors air safety investigator is among the company officials participating in the NTSB investigation.
The "Alaska Aircrash Investigations" episode covering Highlander's death will air at 8 p.m. Sunday. It will also cover another fatal crash last summer, in which 54-year-old Michael Zagula died when his plane hit trees during low passes over his daughter's Trapper Creek wedding reception. On Tuesday, the NTSB said marijuana and diazepam were found in Zagula's system, but it couldn't determine whether they were a factor in that crash.