Upgrades to the Caution and Warning System of the Space Shuttle

During a Space Shuttle mission, astronauts are alerted to off-nominal conditions via a Caution and Warning System that often generates a myriad of auditory and visual alerts. A key component of this system is the Fault Summary display, which contains text messages describing the malfunctions. The display often becomes cluttered with extraneous messages, increasing the difficulty of diagnosing a malfunction. In an effort to improve the crew's diagnostic performance, increase their situational awareness and reduce their workload, the Caution and Warning System is being improved as part of the Cockpit Avionics Upgrade. In the first phase of the upgrade, the Fault Summary display is being redesigned with a more logical task-oriented graphical layout and multiple text fields for malfunction messages. In the second phase, the text fields will indicate only the source (i.e., root-cause) of the malfunction to prevent non-operationally useful messages from appearing on the display. These and other aspects of the upgrades are based on extensive collaboration among astronauts, engineers, and human factors scientists. This paper describes the human factors principles applied to upgrading the Caution and Warning System in the presence of inherent limitations associated with legacy manned spaceflight vehicles.