What happened
On 11 January 2025, a Cessना 510, registered VH-SQY, was performing a medical air transport mission from Narrandera Airport to Bankstown Airport, New South Wales. During the landing phase at Bankstown, the aircraft encountered reduced braking effectiveness, leading to the aircraft overrunning the end of the runway.
Prior to departure, the pilot assessed the landing distance based on a forecast of wet runway conditions. Although the pilot used a conservative assumption of a 5 kt tailwind, the pilot relied on an 80% landing distance factor rather than the required 60% factor. During the descent, the pilot reviewed updated aerodrome information via ATIS, which indicated a wet runway and variable winds. However, the pilot did not identify that the available distance was insufficient for the actual conditions.
During the approach, the aircraft encountered an undetected tailwind, resulting in a touchdown groundspeed exceeding the minimum aquaplaning speed. The presence of standing water on the runway, combined with main landing gear tyres that were worn to their limits, further compromised braking. The situation was exacerbated when the pilot cycled the anti-skid system, which likely decreased braking performance and contributed to the runway excursion.
The investigation
The investigation examined the operator's procedures and the pilot's training protocols. It was found that the type rating training provided by Air Link instructed pilots to use an 80% landing distance factor, whereas Part 135 regulations for a twin-engine jet of this weight require a 60% factor. This practice effectively reduced the safety margin intended to mitigate performance variations.
Furthermore, the investigation looked into the operator's flight planning software, the APG iPreFlight App, which defaulted to the 80% factor option. The investigation also noted that the operator's procedures lacked clarity regarding how to apply landing distance factors, when to conduct in-flight assessments, and how to account for runway surface conditions. Additionally, the training allowed for the use of advisory wet runway performance data from the aircraft flight manual, which was not permitted for official flight planning.
Findings
- The type rating training taught pilots to apply an incorrect landing distance factor, reducing the safety margin.
- The operator's procedures were ambiguous regarding the application of landing distance factors and the necessity of in-flight assessments.
- The flight planning software defaulted to an incorrect landing distance factor.
- The aircraft's main landing gear tyres were worn to their limits, reducing braking capability.
- An undetected tailwind and the presence of standing water contributed to the aircraft's inability to stop within the runway limits.