Display Scaling of Degraded Visual Environment Helicopter Symbology in Station-Keeping Tasks

Abstract

Unexpected encounters with degraded visual environments (DVE) pose a serious risk to rotary-wing aircraft. Due to the loss of outside visual references, pilots engaged in DVE become entirely reliant on cockpit displays and instrument information to land safely. Flight symbology systems have been accordingly developed which offer a set of symbolic cues meant to replace the pilot's lost visual cues. Prior to engaging in operational use, symbology systems must undergo a certification process in part comprised of tuning the display scaling (i.e. the manner in which physical states are scaled to units representable on the display). At present, tuning is conducted through trial-and-error according to the feedback of the test team, without applying quantitative rigor to the process. The premise of this investigation is therefore to prove the existence of a predictable relationship between display scaling and pilot response, and in doing so provide a quantifiable and defendable basis for the tuning process. An experiment is designed in which participants conduct a single-axis precision hover using a pared-down, non-conformal symbology system. During the experiment, three display scalings are varied: the acceleration cue scaling K a , the velocity cue scaling K v , and the position cue scaling K x . A fourth independent variable, Lead, is also considered, which represents the amount of velocity prediction afforded by the acceleration cue. The response is measured according to the root-mean-square (RMS) of the position error, the control activity, and the Bedford workload ratings. From the generated trends, suggested scaling and Lead levels are selected as those simultaneously resulting in low RMS, low control activity, and low workload: K x = 175 f t screen , K v ≈ 22 kts screen , K a = 15 f t s 2 screen , and Lead = 2-2.5 s. Participant control aggression is then captured through the maximum attitude excursion and the time taken to complete the precision hover in an attempt at explaining anomalous responses.iii

Development and Evaluation of Cueing Symbology for Rotorcraft Operations in Degraded Visual Environment (DVE)

“…Flicker is eliminated via the use of hysteresis. For the Bell 412, the transition condition for hover to cruise symbology and vise-Versa at 60 knots [78]. Figure 62 describes via flow chart the display conditions on how to switch between the two symbology.…”

“…Figure 62 describes via flow chart the display conditions on how to switch between the two symbology. [78].…”

Development and Evaluation of Cueing Symbology for Rotorcraft Operations in Degraded Visual Environment (DVE)

“…Flicker is eliminated via the use of hysteresis. For the Bell 412, the transition condition for hover to cruise symbology and vise-Versa at 60 knots [78]. Figure 62 describes via flow chart the display conditions on how to switch between the two symbology.…”

“…Figure 62 describes via flow chart the display conditions on how to switch between the two symbology. [78].…”