Design of a Primary Flight Display to Avoid Decelerating Below the Minimum Safe Operating Speed

Analysis of recent airliner accidents and incidents identified a class of events in which structurally, mechanically, and electronically sound aircraft decelerated through the minimum safe operating speed for the phase of flight to the stick-shaker activation speed. Despite the differences in the sequences of events, a subset of the incidents and accidents had one thing in common – the automation was no longer actively controlling to the airspeed target. This article describes the accident scenarios and design of a modification to the airspeed tape on the primary flight display to explicitly annunciate the absence of active speed control. An experiment to evaluate the efficacy of the enhanced airspeed tape showed faster pilot response time but no differences in correct pilot response.