Tricky light may have been issue in 2016 Anaktuvuk Pass plane crash
Tricky winter conditions may have contributed to the plane crash that happened in the mountains outside Anaktuvuk Pass the day after New Year's last year.
The passenger plane, operated by Wright Air Service and traveling from Fairbanks to the village, had no known mechanical issues at the time of the accident, according to a factual report issued by the National Transportation Safety Board (NTSB) in June. However, the pilot, who was flying by visual flight rules (VFR) in visual meteorological conditions (VMC), said a type of optical illusion that can happen in winter made it difficult to see where he was in the moments before the crash.
Factual reports like this one do not explicitly state investigators' findings regarding the causes of crashes, but rather outline information known about the incident. Investigators' conclusions will be released in a final report to follow.
As the Sounder reported the week of the accident, the crash happened on a mountainside in the Brooks Range, about six miles from the Anaktuvuk Pass Airport, just after noon on Jan. 2, 2016.
"Immediately following the accident, a passenger used a cellphone to call for rescue from Anaktuvuk Pass residents," the report noted.
Word of the crash quickly spread through the village and locals gathered up gear, first aid supplies, warm blankets, loaded it onto sleds, and rode up the mountain as fast as they could.
"I just started crying [when I heard] because, especially in the Brooks Range, when there's a plane crash, there's so many boulders — people don't survive," local resident Homer Mekiana told the Sounder at the time.
Mekiana was one of the dozens of people who mobilized within minutes to attempt a rescue. They didn't know what they'd find on the mountainside — how many survivors and in what condition.
The responders were relieved to find there had been no casualties. According to the report, five of the plane's occupants, including the pilot, were seriously injured. Three other passengers sustained minor injuries. All of the survivors were packed onto sleds and transported down the mountain to the village, where they received emergency medical treatment before being medevaced out.
"With us guys up there on the mountain, our village and our ladies started cooking soup and spaghetti and making coffee for all of us. Everybody pitched in. There was at least 100 people in the clinic; it was that packed," Mekiana told the Sounder last year. "We all stayed until all the people from the crash were evacuated."
Two safety inspectors from the Federal Aviation Administration (FAA) arrived on scene the following day to assess the crash site and wreckage of the Cessna 208B. They found the wreckage at an elevation of about 2,500 feet MSL, or mean sea level, meaning above sea level. The airplane had initially crashed on a ridge about 500 feet above and then slid down to its resting site.
Inspectors recovered some of the wreckage for further assessment.
"The examination revealed no pre-impact mechanical malfunctions or anomalies with the airplane or engine that would have precluded normal operations," the report noted, meaning nothing was found to be mechanically wrong with the plane that could have caused the crash.
During the course of the investigation, inspectors talked to the pilot about the moments before the crash. The pilot said he hadn't heard the Terrain Awareness Warning System (TAWS), which alerts pilots when they're too close to the ground, go off. However, there was no way to check whether or not it had been functioning normally before the crash, inspectors noted.
The pilot, age 57, held a current license with all appropriate ratings and had a current medical certificate allowing him to fly. He had also successfully completed crash avoidance training the year before. Toxicology data showed no signs of drugs or alcohol in the pilot's system at the time of the crash.
In recalling the day of the crash, the pilot described for investigators a well-known optical illusion that can happen in snowy places in winter, called flat light.
As defined by the FAA, flat light can make pilots disoriented by causing them to lose depth perception and contrast in vision. "... Flat light can completely obscure features of the terrain, creating an inability to distinguish distances and closure rates," the report noted. It often happens when the sky and the ground appear the same color — overcast and grey or white with snow, as in this case.
A METAR, or type of aviation weather update pilots check in flight, reported broken clouds at 4,400 feet, overcast conditions at 5,000 feet, and a visibility of six statute miles, at 11:56, about 10 minutes before the crash.
However, FAA weather camera footage from the Anaktuvuk Pass Airport that day paints a somewhat different picture from the METAR. Weather conditions appeared to be varying significantly in different places around the airport. The METAR was not incorrect, but the cameras that recorded data in four directions showed "deteriorating weather conditions about the time of the accident," the report noted.
The south-facing camera footage from 11:52 a.m. to 12:12 p.m. indicated a cloud ceiling below 4,100 feet and visibility of less than two miles.
"Overall, the camera images showed that, although conditions were marginal VFR at the surface at the time of the accident, there was mountain obscuration and reduced visibility due to light snow and clouds along the accident flightpath and that the worst conditions existed along and near the higher terrain at the time of the accident," the report noted.
Additionally, investigators learned that another pilot, who had just taken off from the village, contacted the Wright Air pilot to give him a heads up about the conditions. "[He] had encountered flat light conditions after departing Anaktuvuk Pass, which was 'compounded by low visibility,' and that, to remain in VMC, he had to turn toward the north side of the valley and initiate a climb," the report noted.
Also, "... The [other] pilot stated that he perceived the flat light and low-visibility conditions were highly localized," meaning the poor conditions were not happening everywhere, only in a few places.
As residents of the village are well aware, weather can change quickly and fiercely in the mountains. Conditions can come and go and take the unsuspecting by surprise.
While the precise cause of the crash has yet to be determined by investigators, local residents and survivors still say they are just relieved by the outcome—regardless of how or why it happened, they are glad, more than a year later, there were no fatalities.
Shady Grove Oliver can be reached at firstname.lastname@example.org.