Thesis
Visual dominance during low-level forward flight in degraded visual environments
University of Iowa
Master of Science (MS), University of Iowa
Summer 2025
DOI: 10.25820/etd.008091
Abstract
Degraded Visual Environments (DVEs) pose critical safety challenges for rotorcraft pilots by eliminating essential visual cues, such as the horizon line and peripheral references, which increases cognitive workload and impairs spatial orientation. In contrast, Good Visual Environments (GVEs) promote visual dominance, enabling pilots to rely on visual stimuli to overide conflicting vestibular or proprioceptive signals, thereby lowering workload demands. This study investigated whether minimal line-based symbology, designed to mimic natural visual cues, can restore visual dominance and support natural visual processing mechanisms such as the optokinetic cervical reflex (OKCR). The experimental setup involved six evaluation pilots flying figure-eight maneuvers in a Mi-2 helicopter equipped with an SA-147 helmet-mounted display (HMD), under three distinct visual configurations: a narrow 30° field-of-view (NFOV) lacking peripheral stimuli, a wide 147° field-of-view (WFOV) incorporating peripheral stimuli, and a natural GVE baseline.
Effectiveness was assessed using a multi-modal framework that incorporated aircraft flight data, OKCR responses, physiological workload indicators, subjective pilot assessments, and qualitative feedback. Results showed that WFOV configurations improved OKCR compensation by 63% over NFOV and increased head scanning behavior by 93%, indicating partial restoration of visual dominance. However, WFOV achieved only 61% of GVE’s workload efficiency metrics, suggesting limitations in replicating full natural visual processing. The analysis established OKCR as an effective quantitative metric for assessing visual dominance, revealing greater complexity than previously understood, with head roll behavior influenced by maneuver phase, turn direction, and bank angle magnitude. Pilots flying under NFOV conditions reported “tunnel vision” and consciously limited head movement to reduce perceptual conflict. These findings demonstrate that minimal line-based symbology can partially restore visual dominance in DVEs, providing insights into the visual elements that contribute to visual dominance.
Details
- Title: Subtitle
- Visual dominance during low-level forward flight in degraded visual environments
- Creators
- Maggie Mayfield
- Contributors
- Thomas Schnell (Advisor)Daniel McGehee (Committee Member)Andrew Kusiak (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Industrial Engineering
- Date degree season
- Summer 2025
- DOI
- 10.25820/etd.008091
- Publisher
- University of Iowa
- Number of pages
- xv, 131 pages
- Copyright
- Copyright 2025 Maggie Mayfield
- Comment
- This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/
- Language
- English
- Date submitted
- 07/28/2025
- Description illustrations
- illustrations, tables, graphs, maps
- Description bibliographic
- Includes bibliographical references (pages 120-127).
- Public Abstract (ETD)
Helicopter pilots face serious safety risks when flying in poor visibility conditions like fog, dust storms, or darkness because they lose sight of critical visual references such as the horizon line and surrounding environment. These degraded visual environments force pilots to rely heavily on cockpit instruments, significantly increasing their cognitive workload and risk of becoming disoriented. In contrast, flying in clear weather with good visibility allows pilots to maintain natural spatial awareness with much less effort. This study investigated whether artificial visual aids (terrain gridlines in the outer vision) displayed in a helmet-mounted display could help restore pilots natural ability to stay oriented when flying in poor visibility conditions.
Six helicopter pilots flew figure-eight maneuvers while we tested three different visual setups: a narrow field-of-view (NFOV) at 30 , a wide field-of-view (WFOV) at 147 , and normal clear weather flying for comparison (referred to as the good visual environment or GVE). The NFOV and WFOV setting was flown in a simulated degraded visual environment with minimal line-based symbology. The study measured various flight outcome measures including head movement patterns, flight performance data, pilot workload measures, and pilot feedback to determine the impact of the line-based symbology in the pilot s outer visual field.
The results showed that the WFOV display significantly improved pilot performance, with a 63% improvement in natural head movements that help maintain orientation and a 93% increase in visual scanning behavior compared to the NFOV. However, the artificial visual aids only achieved about 61% of the effectiveness seen in clear weather flying, indicating that while helpful, the line-based symbology in the outer vision did not fully replace natural vision. Pilots consistently identified the horizon line as the most important visual reference, often preferring it over additional display elements that could create clutter. The NFOV display created serious challenges, with pilots reporting tunnel vision effects and difficulty maintaining proper orientation.
This research confirmed that artificial visual aids can meaningfully improve helicopter pilot safety in poor visibility conditions by restoring some natural orientation abilities. The findings provide further insight into the visual elements that support natural flying tendencies.
- Academic Unit
- Industrial and Systems Engineering
- Record Identifier
- 9984948643002771
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