What happened
In two separate flight operations, crews intended to utilize a full flap landing configuration, which is less frequently used. During the approach phase, the flight crews entered the associated VREF and VAPP speeds into the flight management system (FMS) based on this full flap plan. However, during the final landing configuration, both crews failed to recall the earlier briefing regarding the full flap setting. Instead, they selected flap 5 for landing. Because the VAPP was programmed based on the full flap settings, the aircraft approached at a speed 8 kt slower than required for a flap 5 configuration. Despite the reduced speed margins, both landings were completed safely.
The investigation
The investigation examined the role of prospective memory and procedural memory in these events. It was noted that the crews rarely operated the Load 25 aircraft type. When configuring the aircraft, the crews relied on procedural memory, reverting to the more familiar flap 5 setting, but lacked the retrieval cues necessary to recall the specific briefing made approximately 2ally 25 minutes prior.
Technical factors regarding the Load 25 software were also reviewed. In this specific software version, the aircraft targets the speed manually entered into the FMS regardless of the actual flap setting. Unlike the Load 27 variant, the Load 25 does not provide a 'check landing flap' alert if the physical flap setting differs from the FMS entry. Furthermore, while crews typically record weather information like ATIS, there was no requirement or established practice to write down or cross-check the briefed flap setting during the before landing checklist.
Findings
- The flight crews failed to recall the previously briefed full flap configuration when performing the before landing checklist.
- The Load 25 aircraft configuration lacks an automated alert to notify the crew when the selected flap setting does not match the FMS input.
- Alliance Airlines lacked a formal procedure requiring crews to cross-verify the briefed flap setting in the FMS against the actual physical configuration during the before landing checklist.
Safety message
Alliance Airlines had no procedure for flight crews to crosscheck the briefed flap setting entered into the flight management system with the actual configuration selected during the before landing checklist.