A Comparison of Control Activity and Heart Rate as Measures of Pilot Workload in a Helicopter Tracking Task

Two qualified test pilots performed a target tracking flight task on a Bell 205 helicopter. Cooper-Harper handling quality ratings confirmed that pilot compensation was proportional to task difficulty. Pilot control activity was measured using the Dynamic Interface Modeling and Simulation System Product Metric (DIMSS-PM) to quantify the number and amplitude of control deflections during each trial. Inter-beat interval measures of heart rate and heart rate variability were also computed to evaluate the pilot's autonomic nervous system (ANS) response to task workload. The DIMSS-PM was positively correlated with task difficulty, as expected based on the dynamics of target motion for each difficulty level. By comparison, the mean and high-frequency (HF) variability of heart beat intervals were negatively correlated with task difficulty, suggesting an increase in ANS arousal with increased pilot workload. Pilot-specific differences were found in the time-dependent relationship between DIMSS-PM, mean heart beat interval, and HF variability, indicating that control activity and heart rate metrics provide asynchronous and complementary information about pilot workload during helicopter flight. NOTATION ANOVA Analysis of Variance ANS Autonomic Nervous System DIMMS-PM Dynamic Interface Modeling and Simulation System Product Metric ECG Electrocardiogram FBW Fly-By-Wire FRL Flight Research Laboratory HR Heart Rate HRV Heart Rate Variability HQR Handling Qualities Rating NRC National Research Council Canada RRI Inter-beat (R-R) Interval RMS Root Mean Square RMSSD RMS of Successive Differences in RRI SDNN Standard Deviation of RRI HF High Frequency (0.15 - 0.4 Hz) LF Low Frequency (0.04 - 0.15 Hz)