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Maintenance error led to fatal Saab 2000 runway overrun accident, Alaska
3 November 2021

Maintenance error led to fatal Saab 2000 runway overrun accident, Alaska

A PenAir Saab 2000 turboprop airplane overran a runway in Alaska because its braking system was compromised by incorrectly wired anti-skid sensors, the NTSB determined.
PenAir flight 3296, overran the runway during a landing attempt in Unalaska, Alaska. The airplane crashed through the perimeter fence, crossed a road, and came to rest on shoreline rocks on the edge of Dutch Harbor. One passenger was killed; another was seriously injured; and eight sustained minor injuries, mostly during the evacuation. The flight crew, the flight attendant, and the other 29 passengers were uninjured.

A post-accident examination of the airplane revealed sensors for the anti-skid system had been incorrectly wired during an overhaul of the left main landing gear. 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. 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.

Noting that systems should be engineered to prevent human errors that could occur during maintenance, the NTSB recommended Saab redesign the landing gear wheel speed sensor wiring to reduce the probability of a miswiring during maintenance operations. Because the captain elected to land on a runway with a reported tailwind that exceeded the airplane manufacturer’s operating limit, the airplane touched down with a higher-than-normal groundspeed. The NTSB said the decision to land with such a tailwind was “intentional, inappropriate, and indicative of plan continuation bias.”

The NTSB also found that when the Federal Aviation Administration approved PenAir to fly in and out of the Unalaska airport with the Saab 2000, they did not recognize that the safety area beyond the end of the runway did not conform to the recommended safety criteria for an airplane in that design category.

TSB Canada: better de-icing equipment and practices in remote and northern airports needed

The lack of adequate de-icing equipment and the practice of taking off without de-icing led to the fatal December 2017 accident involving a West Wind Aviation ATR-42 aircraft in Canada, according to the TSB investigation report (A17C0146).

On 13 December 2017, the ATR 42-320 aircraft departed Fond-du-Lac Airport, Saskatchewan, Canada. Shortly after takeoff, the aircraft collided with trees and terrain. The aircraft was destroyed. All 22 passengers and three crew members on board were injured, ten of them seriously. One passenger died days later.

The investigation found that, well before the accident, during the descent toward Fond-du-Lac, the aircraft encountered icing conditions. The flight crew activated both the anti-icing and de-icing systems, but some ice remained on the aircraft. However, the crew did not notice any handling abnormalities and landed without incident. During the 45 minutes on the ground prior to the accident flight, icing conditions continued to be present, and additional ice formed on the aircraft. After carrying out a pre-flight inspection, the first officer notified the captain of the presence of some ice on critical surfaces, but there was no further discussion or action taken. Because the available inspection equipment was inadequate, the first officer’s ice inspection consisted of walking around the aircraft, at night, on a dimly lit apron, without a flashlight, and looking at the left wing from the top of the stairs at the left rear entry door. As a result, the full extent of the residual ice and ongoing accretion was unknown to the flight crew.

Departing from remote airports, such as Fond-du-Lac, with some amount of surface contamination on the aircraft’s critical surfaces, had become common practice, in part due to the inadequacy of de-icing equipment or services at these locations. The past success of these adaptations resulted in the unsafe practice becoming normalized and this normalization influenced the flight crew’s decision to depart.

During takeoff, the aircraft initially climbed; however, immediately after liftoff, the aircraft began to roll to the left without any pilot input. This roll was as a result of asymmetric lift distribution due to uneven ice contamination on the aircraft. This loss of control in the roll axis, which corresponds with the known risks associated with taking off with ice contamination, ultimately led to the aircraft colliding with terrain.

This investigation also revealed a number of instances in which Transport Canada’s surveillance policies and procedures were inconsistently applied to the oversight of West Wind Aviation. For instance, between 2010 and 2013, TC had identified several concerns with West Wind’s Safety Management System (SMS). Despite this, TC decreased its surveillance of the company to a detailed inspection only every four years. When a detailed inspection did take place in 2016, it found “systemic failures” with the company’s SMS. Rather than issuing a Notice of Suspension, TC selected Enhanced Monitoring, a more moderate course of corrective action. If the application of Transport Canada’s surveillance policies and procedures is inconsistent, there is a risk that resulting oversight will not ensure that operators are able to effectively manage the safety of their operations.

Following the occurrence, West Wind has taken steps to improve its internal risk assessments, and now provides additional training, guidance, and better de-icing equipment to its crews.

Report: Take-off from closed runway highlights importance of checking NOTAMs

A Swearingen Merlin IIIB twin-turboprop aircraft sustained substantial damage when attempting to take-off from a runway that had been closed for repair works, an ATSB investigation details

The Swearingen SA226-T Merlin had landed at Gunnedah, Australia, on the afternoon of 19 August 2020, and was parked there overnight.  
The following morning, in line with a NOTAM published the previous day closing the runway from 0700 to enable runway repair works, a work crew had excavated two holes from the runway pavement (measuring 3 m wide by 5 m long and about 30 cm deep). 
That afternoon, at about 1230 while the work crew was off-site from the airport during their lunchbreak, the Merlin pilot commenced a take-off run on the runway for a flight to the Gold Coast. 
As the aircraft accelerated, the pilot saw the two rectangular holes excavated from the runway pavement. The pilot attempted to avoid the holes, but they were struck by the aircraft’s left main landing gear.  The aircraft veered off the runway; the pilot – the sole occupant on board the aircraft – was uninjured. 

The ATSB investigation found that during pre-flight planning, the pilot had not checked for relevant NOTAMs, including one stating that Gunnedah Airport was closed due to works in progress.
The investigation also found that while the work crew was away on their lunch break there was no works safety officer on site. Further, while a white cross had been placed at the main windsock, visible to aircraft arriving overhead, there were no ground-visible unserviceability markings on the runway as required by the Civil Aviation Safety Regulations Part 139 Manual of Standards (MOS) for Aerodromes.  This requirement had recently been changed.

The Gunnedah Airport operator had not received notification of the updated MOS because the email included on CASA’s mailing list was for a member of staff who had left the operator. No autoreply, forwarding, or ‘hard bounce’ was in place on the email address, so CASA was not aware the email had not been received. . 

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Screwdriver tip left in engine during maintenance results in engine failure on take-off

An engine power loss and rejected take-off incident involving an Airbus A320 at Brisbane Airport occurred after a screwdriver tip was left inside the engine during maintenance, an Australian Transport Safety Bureau investigation notes.

On 23 October 2020, the Jetstar Airways operated A320 was departing on a scheduled passenger flight from Brisbane to Cairns.
As power was being applied for take-off, the crew felt a vibration and heard a popping noise, which rapidly grew faster and louder. At the same time, the aircraft diverged to the right of the runway centreline despite the first officer applying full left rudder pedal.
The captain immediately selected reverse thrust and brought the aircraft to a stop.

Some of the passengers onboard the aircraft, a Brisbane tower air traffic controller, and flight crew of a following aircraft reported momentarily seeing flames coming out of the right engine.

The aircraft was taxied back to the airport gate, and all passengers and crew disembarked safely.

Engineers then reported finding metallic debris in the tailpipe of the aircraft’s right engine. On disassembly, it was discovered the engine’s high-pressure compressor had sustained significant damage. A removable screwdriver tip was found in the engine’s combustion section.

The ATSB’s investigation determined the screwdriver tip had been in the engine for over 100 flights.

The liberated blade then caused greater damage to the engine’s high pressure compressor, and the engine surged, resulting in the loss of power and the low-speed rejected take-off.