Fatal SAAB Overrun Report Disputed...

[TheGreenGoblin]

Conclusions of a report by the US National Transportation Safety Board (NTSB) into a fatal 2019 overrun involving a PenAir Saab 2000 have been disputed by Swedish and UK investigators.



The report concluded that cross-wiring of the aircraft’s antiskid braking systems led to the crash which killed one passenger and seriously injured another.

The Swedish Accident Investigation Authority (SHK) and the UK Air Accidents Investigation Branch (AAIB) submitted a letter outlining their dissenting opinion that it was a series of operational factors that were the primary cause of the accident.

The crash occurred while the crew of the turboprop, N686PA (c/n 2000-017) were attempting to land at Unalaska Airport in Alaska on October 17, 2019.

After a go-around during the first approach to runway 13, the Swedish-built type entered the circuit for a second attempt on the same landing strip. Shortly before touchdown, the crew were alerted to the wind which was reported to be 300° at 24kts, indicating a significant tailwind of 15kts.

The report stated that a landing on the opposite runway would have favoured the conditions at the time. However, the pilots continued with the plan to land on runway 13.

The captain reported that when the aircraft touched down, initial braking action was normal but that, as the turboprop travelled down the runway, it had “zero braking” despite the application of maximum brakes.

Papa Alpha overran the end of the runway and the adjacent 300-foot safety areas which is designed to reduce damage during an overrun. As a result, of the three crew members and 39 passengers on board, eight sustained minor injuries, most of which occurred during the evacuation.

The fatally and seriously injured passengers were seated in 4A and 5D, respectively. The left side of the fuselage sustained severe damage when the left-hand engine’s propeller blades detached the hub after striking a four-foot chain-link fence and an eight-foot road sign after leaving the runway.

The probable cause of the accident was identified by the NTSB as being the landing gear manufacturer’s incorrect wiring of the wheel speed transducer harness on the left main landing gear during an overhaul in 2017.

The maintenance error caused the antiskid system to not function as intended, resulting in the failure of the outboard tire and the significant loss of braking ability, which, according to US investigators, led to the runway overrun.

Contributing factors to the incident include Saab’s design of the wheel speed transducer wire harness, which according to the NTSB, did not consider and protect against human error during maintenance.

The Federal Aviation Administration’s (FAA) lack of consideration of the overrun safety area at the airport during the authorisation process that allowed the Saab 2000 to operate to the facility was also cited as a factor in the incident.

The NTSB concluded that the safety margin was further reduced because of PenAir’s failure to correctly apply a company-designated pilot in command (PIC) airport qualification policy, which enabled the captain to operate at one of the most challenging sites in the airline’s route network with limited experience at the airport and in the Saab 2000.

In response to the NTSB report, the SHK and the AAIB submitted a joint letter outlining their dissenting opinion of the probable cause identified by their American counterparts.

The pair said they considered the operational factors of landing the aircraft from an unstable approach, “in reported wind well beyond the aircraft limitations, on a challenging runway without full consideration to the aircraft performance at time of arrival” as the primary cause of the accident.

They argue that the aircraft had made many successful flights with the antiskid anomaly, including several to the accident airport; all without incident.

“We consider it is the intentional exceedance of the aircraft limits, on a limited runway, that revealed the previously hidden latent antiskid anomaly, and both were required to cause the accident,” the letter read.

https://www.key.aero/article/uk-and-swe ... 00-overrun

[TheGreenGoblin]

Given the wind direction and the approach with a tail wind, the Captain's landing was clearly a significant factor in this accident. The UK AAIB and the Swedes seem, IMHO, to be in the right of it!