A commercial aircraft overran the runway in Unalaska in 2019, killing a passenger, because its braking system was compromised by incorrectly wired anti-skid sensors, the National Transportation Safety Board determined at a hearing on Tuesday.
The plane, operated by a Ravn Air Group subsidiary, also touched down with higher-than-normal speed because the captain chose to land on a runway with a reported tailwind over the plane manufacturer’s operating limit, the board found.
The Federal Aviation Administration’s erroneous decision to approve the Saab 2000 for landing at the demanding Unalaska airport without a long enough runway safety zone also played a role.
The board unanimously approved 10 safety recommendations, the majority addressing the FAA as well as checking for possible wiring issues on the Saab and addressing the potential for human error. The board recommended Saab redesign the landing gear wheel speed sensor wiring to reduce the probability of a miswiring during maintenance operations.
The turboprop operated by Ravn Air Group left Anchorage with 42 passengers and crew and overran the runway at Unalaska in October 2019, killing one passenger and injuring nine others. The short Aleutian runway is notoriously challenging, flanked on both sides by water at the base of a mountain.
The death of 38-year-old Washington state resident David Allan Oltman — killed when parts of the plane’s propeller pierced the plane’s cabin — was the first crash-related fatality for a U.S. commercial passenger airline in a decade.
A propeller separating and entering a cabin is very rare, leading to just two serious injuries in the past 38 years over millions of flights, chief crash investigator Sathya Silva said during the hearing.
PenAir Flight 3296, a Saab SA-2000, was making a second attempt to land in windy conditions when the accident occurred. Reports contained in a massive docket released last year identified the flight crew as first officer Justin Lunn, 39, and captain Paul Wells, 56.
The pilots missed the first landing and, going around for another approach, Wells suggested landing into a headwind from the other direction, investigators found.
A minute or so before touching down, the pilots checked the wind and a local observer reported a 24-knot tailwind — far higher than the 15 knots both men knew the Saab was rated for, investigators said. But they decided to stick with the original plan, landing with a tailwind later estimated at 15 knots.
Wells knew the other approach was preferable based on the wind but didn’t push for it, investigators found.
Both men had barely 100 hours flight time into Unalaska, far less than the 300 hours that PenAir, the prior carrier on the Unalaska route, had required of its pilots.
An NTSB aviation safety division chief, Marvin Frantz, told the board that the Ravn Air Group subsidiary operating the flight “misapplied” a waiver provision so Wells could fly the route.
That led to “a captain operating at one of the most demanding airports in (the) system with limited experience in the airplane and at the airport,” Frantz said.
Pilots also told investigators they were reluctant to voice safety concerns.
The plane came down hard, passengers reported at the time. At some point, a left tire blew. A surveillance camera video played during Tuesday’s hearing showed the plane careening into view, smoke or dust rising from its left side, before it veered sharply left.
The aircraft crashed through a perimeter fence, crossed a road and came to rest on shoreline rocks at the harbor’s edge.
But with normal braking, investigators found, the plane still should have been able to stop safely.
A post-accident examination of the plane revealed sensors for the anti-skid system had been incorrectly wired during an overhaul of the left main landing gear in 2017, investigators found.
This configuration led to the skidding and bursting of one tire and the subsequent release of brake pressure on two of the three remaining wheels, the NTSB said in a statement. Investigators determined the loss of effective braking on three of the four main landing gear wheels prevented the flight crew from stopping on the runway.
The mistake was hard to discern and wouldn’t be easily spotted during maintenance or visible to pilots checking equipment.
The plane didn’t go into service until June 2019 — about four months before the crash, investigators said Tuesday. There were few red flags about bad wiring except for an unspecified warning four days before the crash and a tire that needed replacement.
The NTSB also found that the FAA certified the Saab to fly into Unalaska despite a 300-foot safety area at the end of the runway. That’s far less than the 1,000 feet required by a plane with the landing speed of that aircraft, investigators said Tuesday.
The board’s staff, in a draft report, recommended a probable cause finding that reflected the crossed wiring and the FAA decision to approve the plane despite the short safety area.
But the board on Tuesday disagreed. An amendment from board member Thomas Chapman raised the pilots’ decision to land in such strong tailwinds to the level of a contributing factor.
“I believe we must place greater emphasis on the role of the crew in this accident,” Chapman said.
The NTSB’s deputy director of aviation safety, David Helson, disagreed. The landing decision was wrong, Helson said, but the plane could have stopped on the runway “if not for the loss of more than 50%” of its braking power.
The board voted unanimously for a probable cause report that included the crew’s landing decision.
The flight was sold by Alaska Airlines and marketed under the PenAir name, short for longtime Alaska carrier Peninsula Airways, which previously flew the Saab 2000s into Unalaska.
On Tuesday, board members and investigators referred exclusively to “PenAir” when discussing the company involved in the crash.
The flight was actually operated by Ravn Air Group subsidiary Peninsula Aviation Services Inc., which bought PenAir’s name and assets including the planes in 2018 after PenAir declared bankruptcy. Before that, the company was scaling back routes due to shortages of mechanics and pilots, NTSB investigators said Tuesday.
Ravn Air Group declared its own bankruptcy in 2020, about five months after the Unalaska crash.
A new company, Ravn Alaska, emerged from bankruptcy proceedings in November.
Ravn Alaska flies into Unalaska but with a different aircraft: the De Havilland Canada DHC-8, known as the Dash 8.
Company CEO Rob McKinney said in a statement Tuesday evening that the company took “great interest” in the NTSB report and agreed with the findings.
The company “intentionally uses aircraft with wider safety margins specifically for this runway,” McKinney said.