Subjective Noticeability of Variations in Quasi-Steady Aerodynamic Stall Dynamics

To collect experiment data on the subjective noticeability of variations in stall dynamics in simulated symmetric quasi-steady stalls, Just Noticeable Difference (JND) thresholds were measured using a passive human-in-the-loop experiment. For a flow separation-based stall model of the Cessna Citation II, these thresholds were determined for variations in the flow separation lag time-constant τ ₁ and the stall abruptness parameter a ₁. Using pairwise comparisons of the baseline model and a model with a parameter offset, a modified yes/no 1-up/1-down staircase procedure was used to measure upper and lower JND thresholds from twelve pilots. The experiment results show that, as also expected from an offline stall model sensitivity analysis, pilots are more sensitive to variations in a ₁ (i.e., 5-10% absolute JND thresholds with respect to the baseline parameter value) than in τ ₁ (20-30% absolute JND thresholds). Furthermore, the upper and lower thresholds were found to be symmetric around the baseline value for both parameters. Overall, the obtained results indicate that human pilots are sensitive even to comparatively small offsets in key stall model parameters, which should thus be considered in the future development of the flight models used for simulator-based stall training.