The use of analog track angle error display for improving simulated GPS approach performance
Abstract:
The effect of adding track angle error (TAE) information to general aviation aircraft
cockpit displays used for GPS non-precision instrument approaches was studied
experimentally. Six pilots flew 120 approaches in a Frasca 242 light twin aircraft
simulator using crosswind and turbulence. 25 mile approach geometries were used,
with and without 45 deg. dogleg turns on final approach. Performance and workload
using three TAE display formats were compared against results with two control formats
presenting cross track error (XTE) only. Pilots found that the TAE displays simplified
determination of wind correction angle, and that they consistently chose to use analog
rather than numeric TAE data. Statistically significant differences between display
formats and between pilots were found. The largest average improvement in initial leg
intercept and tracking performance resulted when the conventional "ten dot" XTE display
was supplemented with a sliding pointer display of TAE, moving in the same direction as
aircraft bank. A second TAE format, a sliding/rotating pointer integrated display,
yielded the greatest improvement (35%) in the width of the short final approach flight
technical error envelope, but pilots reported occasional problems interpreting this
display. Both of these TAE formats improved final approach intercept and tracking
performance after 45 deg. turning maneuvers. Addition of TAE information to the receiver
display helps pilots create outer loop lead, and yielded approach performance improvements
comparable to relocating XTE information to an HSI within the pilot's primary scan.
Bedford workload scores were not significantly influenced by display format, but were
found to depend on approach geometry and phase. Keywords: man/machine interfaces,
displays, manual control, simulators, aircraft control, flight control, air traffic
control, multiloop control, mental workload, global positioning systems, navigation
systems. Supported by Department of Transportation Contract DTRS-57-92-C-0054 TTD#27.
