Four people who died when a plane they were flying in crashed near St. Mary’s last month faced highly variable visibility that caused another plane to turn back shortly before the accident, according to a preliminary report released Oct. 3 by the National Transportation Safety Board (NTSB).
The Cessna 207 took off from Bethel and was operated as a private flight by Bethel-based carrier Yute Commuter Service. It crashed just after 10 p.m. on Sept. 15 within a couple thousand feet of the runway serving the lower Yukon River community of St. Mary’s, according to the report.
The report says that minutes before the crash, the plane overflew the smaller of two runways at the St. Mary’s airport twice, before making an ultimately fatal steep right descending turn toward the ground.
Weather conditions at the St. Mary’s airport just before the crash were light rain and mist, with visibility of roughly 2.5 miles. But according to NTSB Alaska Chief Clint Johnson, the precise weather conditions that may have led to the crash are still unknown.
"Not knowing exactly what the weather conditions were at the time, it could be that it was obscured by fog, by some type of visibility restriction, that we don't know," Johnson said. "We just don't have that part of the equation."
The report also notes that the Cessna 207 was equipped with an aircraft positioning system known as Automatic Dependent Surveillance–Broadcast (ADS–B) that can allow aircraft to be closely tracked by air traffic control. But air traffic control received no data during the flight from Bethel to St. Mary’s, according to the report.
"It obviously allows air traffic control to be able to keep track of the airplane, but it also gives the pilot a tremendous amount of information as far as situational awareness," Johnson said. "And so we really don't know if it could have played a part in it here, but obviously our investigation will be looking at, you know, some of the circumstances, or some of the reasons why there wasn't an ADS-B track on this one."
At the time of the crash, the plane was traveling under what is known as special visual flight rules (VFR) clearance, which allows aircraft to land when visibility is below what is necessary to rely on vision alone.
Around a half-hour before the fatal crash, another plane attempting to land at St. Mary’s under special visual flight rules clearance, also operated by Yute Commuter Service, made the decision to turn back and return to Bethel. The pilot told investigators that weather conditions at the time were “going up and down a lot,” and that conditions at St. Mary’s were "fogged in."
"As you can see from the interview that we did with the pilot that turned around and came back to Bethel, the weather was very dynamic, where it was changing on a minute by minute basis," Johnson said. "And that is very standard, very un-unique to that area out there."
That pilot also noted that the lights on the shorter runway at St. Mary’s were not operational just before the other plane’s crash.
"There were some runway lights that were out of service. That is going to be a big part of our investigation as well," Johnson said.
According to the report, the plane’s pilot, 34-year-old Scott Grillion of Chugiak, served as Yute’s assistant chief pilot at the time of the crash. Passengers included another Yute pilot, 23-year-old Mario Gioiello of Ohio; a former Yute pilot, 25-year-old Caleb Swortzel of South Carolina; and another man, 44-year old Benjamin Sweeney of Sterling. The four were reportedly headed out on a moose hunt.
The report also notes that the Cessna 207 was not authorized for charter operations at the time of the crash because it had exceeded the number of hours required between engine overhaul or replacement. But according to Johnson, using aircraft not approved for charter operations for things like flight training, as Yute had reportedly done with the plane, is nothing out of the ordinary.
According to the report, the airplane wreckage was recovered and transported to Wasilla, and a more detailed NTSB investigation and report is pending.
