A brake failure and fire that triggered the evacuation of a Dash 8 passenger aircraft at Sydney Airport demonstrates the importance of appropriate operational guidance in modern aircraft with complex, integrated systems, an Australian Transport Safety Bureau final report states.
On 8 November 2022, the QantasLink-operated Dash 8-202 was on descent into Sydney on a flight from Lord Howe Island when its radio altimeter (RadAlt) failed.
This failure was accompanied with similar notifications for the traffic alert and collision avoidance system (TCAS), and the ground proximity warning system (GPWS), which rely on the RadAlt to function.
After consulting the Quick Reference Handbook, the flight crew proceeded with a visual approach and landing. During landing, the beta lockout system horn activated.
“In a turboprop aircraft such as the Dash 8, the beta range is the range of power lever positions between flight idle and maximum reverse,” ATSB Director Transport Safety Kerri Hughes explained.
“Beta mode provides for minimum thrust by controlling blade pitch, and is designed for use only on the ground.
“As such, to prevent the use of beta range during flight, beta lockout can activate based on interlocking signals from the RadAlt and the weight on wheels sensors.”
In this occurrence, the failure of the RadAlt meant the beta lockout was reliant solely on the weight on wheels sensors.
“Flight data showed that, in the same second the power levers were retarded to beta range, the weight on wheels sensors recorded a momentary ‘in-air’ condition, which activated the beta lockout system,” Ms Hughes explained.
The beta lockout resulted in manual caution warnings for both engines, as the engine control units reverted to manual mode.
This meant the captain had to manually advance the power levers during taxi, which subsequently increased the amount of wheel braking required.
“Having landed on Sydney’s runway 34R, the aircraft had to taxi around 5.5 km to the terminal,” Ms Hughes said.
“The long taxi, coupled with the higher-than-usual amount of wheel braking, resulted in the brakes overheating, failing, and igniting during the aircraft’s final turn at the terminal area.”
The cabin crew reported to the pilots via the interphone that there was fire, including visible flames, from both sides of the aircraft, and the captain initiated an evacuation.
The aircraft was safely evacuated, and the fire was extinguished.
The ATSB’s investigation concluded the operator did not provide adequate guidance on how to respond to a dual engine control unit or radio altimeter failure on the Dash 8 aircraft, leaving flight crew without sufficient resources to appropriately deal with such failures.
QantasLink has subsequently made changes to the relevant Quick Reference Handbook and Flight Crew Operating Manual to provide further information about the beta lockout system, and new checklists for a RadAlt failure.
“This occurrence highlights the importance of appropriate operational guidance, particularly in modern aircraft with complex integrated systems,” Ms Hughes said.
“Procedures for managing an equipment failure should consider factors that may influence the performance of other operational systems – in this occurrence, the flow-on effects of the radio altimeter failure on the beta lockout system.
“Fortunately, the flight crew were able to successfully troubleshoot the system errors and carry on the flight safely.”
You can find here the report: Brake failure and fire involving DHC-8-202, VH-TQS, Sydney Airport, New South Wales, 8 November 2022
