A series of studies was conducted to improve the Army aviator's ability to perform night missions by developing innovative symbols that capitalize on the advantages of new wide field-of-view (WFOV) helmet-mounted displays (HMDs). The most important outcomes of the research were two new symbol types called the Cylinder and the Flight Path Predictor. The Cylinder provides a large symbolic representation of real-world orientation that enables pilots to maintain the world frame of reference even if the visibility of the world is lost due to dust, smoke, snow, or inadvertent instrument meteorological conditions (IMC). Furthermore, the Cylinder is peripherally presented, supporting the “ambient” visual mode so that it does not require the conscious attention of the viewer. The Flight Path Predictor was developed to show the predicted flight path of a maneuvering aircraft using earth-referenced HMD symbology. The experimental evidence and the pilot interview results show that the new HMD symbology sets are capable of preventing spatial disorientation, improving flight safety, enhancing flight maneuver precision, and reducing workload so that the pilot can more effectively perform the critical mission tasks.
New HMD symbols, specifically designed for wide-field-of-view (WFOV) application, were dynamically prototyped using a WFOV helmet mounted display (HMD) in conjunction with the PRISMS helicopter flight simulator. Missions were flown through realistic terrain by an expert Apache pilot. The data indicate that: (1) Pilot performance, in almost all measures, is substantially improved with use of a WFOV (99), as compared to a narrow-field-of-view (NFOV) (40) display; (2) Earth-fixed navigational and tactical symbols improve navigation accuracy, enhance aircraft handling performance, improve target acquisition, and reduce pilot workload; (3) Best performances were typically exhibited using WFOV with the new symbols-- neither the WFOV nor the symbols alone could produce peak perform-ance; (4) A flight path marker symbol showing the aircraft velocity vector improves aircraft handling and reduces workload, especially when paired with a WFOV display; (5) The new symbols were valuable even in complete darkness, showing that the superiority of the WFOV is due not only to broader views of the terrain, but also to broader views of effectively designed symbology; and (6) The additional area of the WFOV display can be used to present useful ancillary data without cluttering the central zone.
An experiment was conducted to compare performances on operational tasks with and without new earth-fixed symbology representing the positions of waypoints, battle positions, and engagement areas. Fourteen experienced AH-64 Apache pilots flew a representative attack mission in the Pilot/Rotorcraft Intelligent Symbology Management Simulator (PRISMS). Performances were significantly better in waypoint crossing accuracy, landing accuracy, engagement area recognition accuracy, and concealment from enemy positions when using the new symbols.
With the emergence of helmet-mounted display (HMD) technologies, unlimited numbers of new flight symbols and symbol behaviors become possible. Rapid, insightful evaluation of these many potential capabilities is imperative. Because flight tests are risky, time-consuming, and expensive, simulators must be employed for the majority of these studies. Unfortunately, existing research simulators often are extremely expensive to construct and operate, dependent upon a team of technical support personnel, time-consuming to reprogram, not portable, and in such demand that it is impossible for most researchers to access them. This paper describes a powerful, but inexpensive, flight simulator specifically developed in response to these shortcomings, providing many of the features of simulators costing hundreds of times as much. The pilot-rotorcraft intelligent symbology management simulator (PRISMS) is easy to operate and is portable for use in a variety of on-site research, demonstration, and training applications. PRISMS includes an immersive, head- tracked HMD, with symbology in screen-, aircraft-and earth- fixed frames of reference, overlaying realistic terrain adapted from the SouthWestern USA database. The system includes cyclic, collective, and rudder pedal flight controls, a helicopter flight model, voice recognition and synthesis, 3D sound generation, user-definable symbol appearance and behavior, and full data recording capabilities.
An experiment was conducted to assess the effects of system lag on head tracking performance when positioning a cursor on a stable target. Seven values of lag were tested: 0, 20, 40, 60, 80, 100, and 120 msec. To assess potential interactions, the effects of lag were examined in combination with movement distance and direction. The task was to move a head-tracked cursor to a target that appeared on a six-inch CRT screen in an analog of time and that lag was linearly related to acquisition time, accounting for an increase in target acquisition time of approximately 7 millisecond of lag. Furthermore, the effects of lag on performance were evident with lags as brief as 20 msec.
To employ the most readily comprehensible presentation methods and symbology with helmet-mounted displays (HMDs), it is critical to identify the information elements needed to perform each pilot function and to analytically determine the attributes of these elements. The extensive analyses of mission requirements currently performed for pilot-vehicle interface design can be aided and improved by the new capabilities of intelligent systems and relational databases. An intelligent system, named ACIDTEST, has been developed specifically for organizing and applying rules to identify the best display modalities, locations, and formats. The primary objectives of the ACIDTEST system are to provide rapid accessibility to pertinent display research data, to integrate guidelines from many disciplines and identify conflicts among these guidelines, to force a consistent display approach among the design team members, and to serve as an 'audit trail' of design decisions and justifications. A powerful relational database called TAWL ORDIR has been developed to document information requirements and attributes for use by ACIDTEST as well as to greatly augment the applicability of mission analysis data. TAWL ORDIR can be used to rapidly reorganize mission analysis data components for study, perform commonality analyses for groups of tasks, determine the information content requirement for tailored display modes, and identify symbology integration opportunities.