Incident Overview
• Date: June 26th, 2024
• Aircraft: de Havilland Dash 8-400
• Registration: VH-QOI
• Operator: Sunstate Airlines (on behalf of Qantas)
• Flight Number: QF-2489
• Route: Horn Island, QL to Cairns, QL, Australia
• Event: Incorrect flap setting for departure
• Outcome: Aircraft successfully climbed and landed safely in Cairns
Summary of Events
Flight QF-2489, operated by Sunstate Airlines, was departing from Horn Island Airport (HID) to Cairns (CNS) with 67 passengers and 4 crew. During the pre-departure planning phase, the crew determined that the takeoff would require a flap setting of 15° due to the runway length and aircraft load. However, the first officer (FO) inadvertently set the flaps to 5°, a setting more commonly used at other airports in the network.
The pilot flying (FO) noticed increased control column pressure during rotation, and the aircraft became airborne approximately 5 knots beyond the expected rotation speed (Vr). Observing that the climb performance was below expectations, the pilot monitoring (PM) verified the trim and speeds, while the FO identified the incorrect flap setting. The crew adjusted the aircraft configuration and continued to Cairns without further incident.
Key Findings
1. Contributing Factors:
• The FO inadvertently set the flaps to 5° instead of the planned 15°, likely due to habitual behavior influenced by previous operations where 5° was standard.
• The pre-departure checklist included multiple opportunities to detect the incorrect setting, but the error went unnoticed due to automaticity and high workload during the pre-flight phase.
• The incorrect flap setting reduced the aircraft’s climb performance and its obstacle clearance capability on departure from Horn Island.
2. Crew Performance:
• The FO applied additional back pressure during takeoff, enabling the aircraft to achieve a safe liftoff slightly beyond the expected rotation speed.
• The crew promptly identified and resolved the issue in flight, maintaining safe aircraft control.
3. Aircraft Performance:
• The incorrect configuration did not compromise the aircraft’s ability to achieve a positive rate of climb but significantly reduced the margin of safety.
ATSB Conclusions
The Australian Transport Safety Bureau (ATSB) identified the following probable causes:
1. Human Factors:
• The FO’s inadvertent selection of flaps 5° resulted from automatic behavior developed through prior routine use of the setting.
• The crew’s high workload during the pre-departure phase increased reliance on habitual behaviors, reducing their sensitivity to errors.
2. Checklist Execution:
• While the crew adhered to standard procedures, the pre-flight checks were conducted with a high degree of automaticity, reducing their effectiveness in detecting the error.
3. Operational Impact:
• The incorrect flap setting reduced the performance envelope, creating potential safety risks during the critical takeoff phase.
ATSB Safety Message
The ATSB emphasized the importance of:
1. Mindful Engagement:
• Flight crews must remain vigilant and focused during high-workload phases, such as pre-flight preparation, to avoid automatic behavior leading to errors.
2. Checklist Discipline:
• Methodical and deliberate execution of checklists is critical for detecting deviations, especially when settings differ from routine configurations.
3. Error Mitigation:
• Enhanced system designs that increase error tolerance and reduce reliance on human vigilance can further improve operational safety.
Analysis
The ATSB analyzed that the slip in flap selection occurred due to the FO’s habitual use of the 5° setting in prior operations. High workload conditions likely amplified reliance on automatic routines, diminishing error detection during the after-start checklist.
During takeoff, the FO’s control inputs compensated for the reduced climb performance, ensuring a safe departure. However, the crew’s reliance on routine behaviors highlighted vulnerabilities in error detection, particularly during time-compressed, high-pressure operational phases.
Recommendations
1. Crew Training:
• Incorporate scenarios emphasizing mindful checklist execution and managing unusual settings into recurrent training programs.
2. Operational Procedures:
• Enhance pre-flight briefings to reinforce the importance of error detection during non-routine operations.
3. System Enhancements:
• Consider automated systems or visual alerts to highlight discrepancies in critical aircraft configurations, such as flap settings.
Conclusion
While the crew’s actions ensured a safe outcome, this incident underscores the importance of vigilance, training, and robust procedures in mitigating human errors. The ATSB’s findings provide valuable insights for improving safety during high-workload phases of flight operations.
Disclaimer
This report is based on publicly available information as of January 21st, 2025. For copyright concerns, contact takedown@cockpitking.com.
