Incident Overview
The flight crew employed the autopilot's vertical navigation path (VNAV PTH) mode and autothrottle to manage the aircraft's descent and airspeed during the arrival. As expected for a clean configuration, the autopilot could not sufficiently reduce speed to simultaneously meet the descent profile and the airspeed restrictions of the standard terminal arrival route (STAR). Without the flight crew adding any drag, the aircraft maintained an airspeed approximately 30 knots higher than the STAR's speed limits. An air traffic controller then issued a speed reduction instruction, leading the crew to modify the aircraft's configuration.
Crew Actions and Workload
The crew perceived the ATC instruction as urgent, which increased their workload. It is likely that they focused their attention on monitoring airspeed and extending flaps promptly but within operational limits. This focus, described as attentional narrowing by Wickens (2021), can cause steps in a linear procedure to be skipped. As the aircraft decelerated to final approach speed and was configured for landing earlier than normal, it is probable that the crew omitted arming the speedbrake and calling for the landing checks because their attention was concentrated on achieving the required speed reduction.
Performance Factors
The captain perceived that their monitoring performance was modestly degraded due to a lack of recent flying experience. During the final approach segment, while the aircraft was on the approach path and at the required approach speed, it did not meet all stabilized approach criteria. Specifically, the landing checklist had not been completed and the speedbrake was not in the armed position.