Rotorcraft autorotation is a particularly challenging and hazardous maneuver. Reasons for this include: 1) Highly coupled aircraft dynamics, 2) Highly non-linear aircraft dynamics, 3) Critical aircraft states must be extracted from various sources that are not co-located, making pilot synthesis difficult, 4) Instrument scales and depiction methods make integration of state information difficult, 5) Pilot unfamiliarity with entry conditions/terminal constraints, and 6) A pilot's scanning strategy must usually undergo rapid and unnatural transitions during the maneuver. This paper puts forward a novel training display and methodology that takes advantage of automation's potential as a high-speed decision aid and the strengths of human pattern recognition and conditioning. The methodology applies optimal control theory to solve for a helicopter's trajectory and the required control inputs. A preview of the commanded input suite is displayed to the pilot, which will dynamically update as the vehicle state changes in time. Using this the pilot should be able to execute numerous autorotation maneuvers previously considered outside the operational envelope, in addition to performing 'standard' autorotations with a high degree of control consistency and accuracy. The preview display's function can also be extended to serve as an on-board pilot cueing aid. An autorotation cue set developed from functional requirements is presented, along with results of a preliminary experiment incorporating the display.
Helicopter flight using night-vision devices (NVDs) is difficult to perform, as evidenced by the high accident rate associated with NVD flight compared to day operation. The approach proposed in this paper is to augment the NVD image with synthetic cueing, whereby the cues would emulate position and motion and appear to be actually occurring in physical space on which they are overlaid. Synthetic cues allow for selective enhancement of perceptual state gains to match the task requirements. A hover cue set was developed based on an analogue of a physical target used in a flight handling qualities tracking task, a perceptual task analysis for hover, and fundamentals of human spatial perception. The display was implemented on a simulation environment, constructed using a virtual reality device, an ultrasound head-tracker, and a fixed-base helicopter simulator. Seven highly trained helicopter pilots were used as experimental subjects and tasked to maintain hover in the presence of aircraft positional disturbances while viewing a synthesized NVD environment and the experimental hover cues. Significant performance improvements were observed when using synthetic cue augmentation. This paper demonstrates that artificial magnification of perceptual states through synthetic cueing can be an effective method of improving night-vision helicopter hover operations.
A preliminary study was conducted to investigate the use of visual flow cues as an aid to ground and vertical drift awareness during helicopter flight and targeting while using night vision goggles (NVGs). Three displays wee compared: (1) NVG display: simulated NVG image of cockpit and external environment. (2) Overlay display: NVG image with an overlay display but with symbology flow cue field and a surrounding wire-frame globe; (3) Cut-out display: same as the overlay display but with symbology removed from the central region. Three levels of contrast were also compared using each display type. The visual scenery was displayed to subjects using a helmet-mounted virtual reality device that had a 40 by 50 degree field-of-view liquid crystal display. The study involved six pilots. Three tasks were given: (1) Search task: designate enemy targets with a helmet-mounted sight; (2) Hover task: null out all transnational and yaw rates while in a hover; (3) Search/Hover task: perform both Search and Hover tasks simultaneously. These tasks were conducted in a fixed-based helicopter simulator which used the dynamics of a small-scale model helicopter. The following performance measures were collected: (1) Pilot ability to detect and recognize targets; (2) Pilots ability to null transnational and yaw rates; (3) Time scanning the instrument panel. Subjects also rated displays for efficacy in completing the three tasks. Target detection scores conducted during the Search and Search/Hover tasks were highest using the NVG display, followed by the cut-out display. Root-mean-square (RMS) drift rate error was comparable for all display types in the Hover and Hover/Search tasks, however RMS control input activity in all the translational axes was significantly higher in both rate-cueing displays than with the NVG display. From the control input and drift rate time histories it appears that the motion cues were more compelling in the overlay and cut- out displays than those perceived in the NVG display. A significant decrease in instrument-scanning time was observed for both the overlay and cut-out displays compared to the NVG display, with pilots flying essentially head-out- of-cockpit while using the rate-cueing displays. Contrast was not observed to have a significant effect on hover performance in any of the displays.
A preliminary study was conducted to investigate the use of reference markers found in the head-fixed frame as an aid to reference frame awareness during aircraft flight while using a helmet mounted display. Three reference-cueing displays were compared: (1) Sparse Reference display: all cockpit and airframe markers removed except for the instrument panel, (2) Cockpit Reference display: entire cockpit environment visible, and (3) Geo/Cockpit Reference display: cockpit environment visible with the addition of a surrounding wire-frame globe. The visual scenery was displayed to subjects using a helmet-mounted virtual reality device that had a 40 X 50 degree field of view liquid crystal display. The study involved six pilots. The task was to locate targets from aural alert information. The aural alerts were based in either the Aircraft reference frame (i.e. target clock position relative to the aircraft nose), or the World reference frame (i.e. target bearing). These tasks were conducted while the subject rode through abrupt maneuvering flight at low level in a fixed-based Cobra helicopter simulator. Performance measures of the pilot's ability to discriminate the intended target from secondary targets in the visual field were collected, as well as subjective ratings for each reference display. The Geo/Cockpit Reference display produced the highest target detection scores for both Aircraft and World-reference alerts. The highest overall detection scores were produced when World-referenced alerts were issued while using the Geo/Cockpit display. The Cockpit display scores were higher than the Sparse display's for both alert types. Subjective scores showed pilot preference for the Geo/Cockpit Reference display over the two displays for both Aircraft and World-reference alerts. A secondary exploratory experiment using the same tasking as the initial experiment was also conducted which observed the effect of peripheral cues. Target detection scores for both alert types decreased when peripheral cues were removed from the Cockpit display. Detection scores also decreased with the removal of peripheral cues from the Geo/Cockpit display during the Aircraft-referenced alerts.
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