Brake Fire Leading to QantasLink Dash 8 Evacuation Linked to Radio-Altimeter Failure During Approach

Australian aviation authorities have concluded that a brake fire incident involving a QantasLink De Havilland Dash 8-200, which necessitated an emergency evacuation, was caused by excessive braking upon landing. This situation arose following a radio-altimeter failure during the aircraft's approach to Sydney on 8 November 2022.

The Dash 8 (registered VH-TQS) was in the midst of its descent, passing through 17,500 feet, when the radio-altimeter malfunctioned. This failure had a cascading effect, disabling the collision-avoidance and ground-proximity warning systems, crucial technologies that depend on accurate radio-altimeter readings, and subsequently alerting the flight crew to the issue.

Complicating matters further, the radio-altimeter plays a vital role in the aircraft's 'beta lockout' mechanism. This system is designed to prevent the selection of reverse thrust during flight by stopping the throttles from being moved into the 'beta' range. Normally, below 50 feet, the lockout is disengaged via the radio-altimeter signal, allowing for reverse-thrust deployment post-landing, with weight-on-wheels sensors providing an additional layer of inhibition.

Due to the radio-altimeter's failure, the beta lockout depended solely on the weight-on-wheels indication as the aircraft landed on Sydney's runway 34R. Flight data revealed that the weight-on-wheels sensors initially confirmed ground contact but briefly flipped back, suggesting airborne status, just as the aircraft fully settled. This fleeting signal mismatch triggered the lockout just as the first officer attempted to engage reverse thrust, leading to a lockout warning.

The situation forced the crew to adjust the throttles out of the 'beta' range to silence the warning, inadvertently causing the engines' control units to switch to manual mode. Unable to utilize reverse thrust, the pilots had to manage propeller speeds manually while also applying more wheel braking than typically necessary.

This increased reliance on wheel braking was further aggravated by an unusually long taxi route of approximately 5.5 kilometers, which included descending terrain. Mid-taxi, the crew detected a drop in braking efficacy. Despite this, the aircraft proceeded but eventually suffered brake overheating and failure upon turning into the domestic parking bay, narrowly avoiding a collision and coming to a stop.

Upon halting, cabin crew alerted the cockpit to visible flames emanating from both main landing gears, prompting the captain to initiate an evacuation. The first officer took immediate action, attempting to douse the flames until emergency services arrived to apply foam suppressant.

Miraculously, all 24 passengers and three crew members exited the incident without injury.

In response, QantasLink circulated technical advisories detailing the incident and outlining the beta lockout system to its flight crews, alongside an updated checklist to recognize and address radio-altimeter failures effectively. These revised protocols emphasize verifying positive weight-on-wheels confirmation before engaging reverse thrust, aiming to prevent similar incidents in the future.