Does the 'silent cockpit' reduce pilot workload?

The introduction of a digital data link between air traffic control and the aircraft cockpit is likely to have an effect of crew situation awareness through the absence of 'party line' information. On the other hand, eliminating the pilots' exposure to background speech may have a positive effect on their workload since speech, by its very nature, has the potential of significantly disrupting other tasks. Whilst the first effect is comparatively well documented in the literature, potential positive effects of the absence of party line information have to date not been studied. This paper reports on an experiment, carried out in a fixed-base flight simulator in order to investigate the effects of the absence of background radiotelephony (R/T) on pilot workload. The experiment involved 24 approaches at a major European airport, which were carried out by four flight crews with and without background party line communication. To be able to assess the impact of the background speech for high levels of workload, all non-precision approaches were flown manually. The analysis was carried out along a number of axes: a variety of psycho-physiological indicators of pilot workload were measured and analyzed, such as heart rate and heart rate variability, eye blink rate, blood oxygen saturation, electro-dermal activity, and electro encephalography (EEG). Performance criteria included checklist completion times, missed ATC calls, and deviations from the approach path. Subjective workload ratings and pilot debriefings provided an additional source of information. The analysis was carried out for the different flight phases encountered during the extended approach, and the respective pilot roles (pilot flying, pilot non-flying). Results suggest that the absence of background speech does in fact have the potential to reduce pilot workload. This effect was observed from performance data and subjective data, and was stronger for the pilot non-flying than for the pilot flying.