JUNEAU — The braking system on a plane carrying 42 people that overran a runway at an Alaska airport in 2019, killing one, was compromised by anti-skid sensors that were not correctly wired, the National Transportation Safety Board determined Tuesday.
The incorrect wiring likely occurred during an overhaul at the landing gear manufacturer’s facility in January 2017, but it was not discovered until after the accident, the report said.
The system “does not generate a fault based on incorrect wiring,” the report said. Also, the plane was not in revenue service from the time of the overhaul until June 2019, the report said. Revenue service refers to flying passengers or cargo for money.
The improper configuration “led to the skidding and bursting of one tire and the subsequent release of brake pressure on two of the three remaining wheels. 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,” a statement from the agency said.
“Even though the airplane, the pilot, the weather and federal oversight all had a role in this tragedy, it was entirely preventable,” the board’s chair, Jennifer L. Homendy, said in the statement.
She described factors the board determined contributed to the accident: “The brake system should have been designed to protect against human error during maintenance, the pilot shouldn’t have landed on a runway with such a strong tailwind and federal regulators should have considered the runway safety area dimensions when authorizing the airline to fly the Saab 2000 into that airport.”
The Federal Aviation Administration approved the use of the plane at the airport without considering whether the runway safety area was adequate for a plane with that approach speed and size, the report said.
Flight crew members told investigators they were aware of the plane manufacturer’s 15-knot tailwind limit, but they thought the reported wind direction and speed of 24 knots did not warrant a change of runway, the report said, calling the decision “inappropriate.”
Before landing, flight crew members learned of 24 knot winds, the report said. Investigators after the accident calculated the tailwind at landing at 15 knots, the report said.
The report said the plane was operated by Peninsula Aviation Services Inc., which it refers to as PenAir. PenAir had designated the airport in the Aleutian Islands fishing community of Unalaska as one requiring specific qualifications for pilots in charge because of the surrounding terrain “and complex approach and departure procedures,” the report says.
But it said the company allowed the captain of the accident flight to fly at the airport “without gaining the experience that the company’s policy intended” and that the captain “might not have fully understood” the challenges in landing the aircraft at that airport.
The flight was operated by a Ravn Air Group subsidiary that bought PenAir’s name and assets in 2018 after PenAir declared bankruptcy, the Anchorage Daily News reported. Ravn Air Group declared bankruptcy last year.
The report, among its findings, said the FAA’s oversight of PenAir in the two years before the accident was insufficient to identify safety risks resulting from such things as the bankruptcy and loss of experienced pilots. A message seeking comment was sent to an FAA spokesperson.
NTSB also made several recommendations to the FAA. The agency, in a statement, said it takes seriously NTSB recommendations and will provide preliminary responses to those within 90 days.
Saab, in a statement, said it has “contributed to the investigation by advising the Swedish Accident Investigation Authority (SHK) and will continue to support the NTSB in the investigation.”