Enhanced HUD Symbology Associated with Recovery from Unusual Attitudes 901919
The present study examined the degree of spatial awareness obtained using what has been called an Augie Arrow, enabled so that it could be displayed as either a “nearest horizon pointer” (NH) or an “up arrow” (UP) indicator. Another issue investigated concerned the usefulness of analog dials vice digital readouts of airspeed and altitude as an aid to recovery. During simulated flight, twelve subjects were required to recover from six unusual attitudes employing one of four HUD formats: (1) Standard HUD, (2) Augie Arrow, (3) Analog Dials, and (4) Augie Arrow with Analog Dials. Results revealed that the Augie Arrow produced the most rapid recovery time. The Augie Arrow configuration was optimal at the most severe unusual attitudes, especially for the NH mechanization. The Dials only HUD was not particularly helpful in recovery, and the Arrow with Dials HUD was rated as a significant clutter problem. Future work needs to be done to clarify the mechanization of the Augie Arrow for other HUD modes, while the issue of when to display the arrow should be assessed in greater detail. Issues related to the difficulty of performing simulation studies in this area were discussed.
A concern among avionics display designers is the degree of spatial/attitudinal awareness achievable with the Head Up Display (HUD). In fact, HUDs have been implicated as likely factors contributing to the loss of situational awareness in military aircraft accidents. The lack of cues to determine upright from inverted flight and the difficulty in determining rate information (airspeed and altitude) using digital readouts, are major drawbacks of using the HUD for attitudinal information. Interestingly, work in this area began almost 15 years ago. Preliminary work by both Barnette (1)* and Newman (2) indicated that 30 percent of pilots flying aircraft with HUD systems reported an increase in spatial disorientation attributed to the use of the HUD. More recent evidence has indicated that inadequate or ambiguous attitude displays in the cockpit pose serious problems and have been identified as contributing to numerous aircraft mishaps where loss of situational awareness or spatial disorientation were listed as confirmed or probable cause factors (3).
With the upgrade of the F-14A aircraft to the F-14D, the current F-14A HUD is scheduled to be replaced. The new HUD will have a superior field-of-view, will provide more information, and will have greater display capabilities. With improved capabilities, the F-14D HUD has been proposed for use as the primary flight reference instrument (such as in the F/A-18). Used in this capacity, attitude awareness becomes a critical concern. The attitude directional indicator (ADI) is currently the conventional flight reference system used for civil and most military aircraft. The ADI provides an artificial horizon allowing the pilot to assess pitch and roll of the aircraft without referencing the earth's horizon. Color coding is used to differentiate pitch attitude above and below the horizon. Thus, the design of the ADI follows the display principle of pictorial realism in that it represents a spatial analog of the real world (4). Direct comparison between the display and the real world is not possible with symbolic displays such as the HUD. In fact, previous research has criticized the use of HUDs as primary flight reference instruments and as aids to recovering from unusual attitudes (5). This concern has been demonstrated in renewed interest in the development of new cues to assess spatial awareness (5, 6, 7). The data from these studies indicated that certain modifications to HUD formats can enhance recovery from unusual attitudes when compared to conventional or standard HUD formats.
The present study examined the degree of spatial awareness that can be attained using what has been called an “Augie Arrow” (6). Preliminary evidence exists which suggests that the Augie Arrow may enhance recovery from unusual attitudes (6, 8). However, no data are available which indicate the proper mechanization of the arrow. In particular, whether the arrow should be displayed as a “nearest horizon pointer” (NH) or as an “up pointer” (UP). Another issue investigated in this study concerned the ability to ascertain altitude and airspeed rate information from the projection of digital vice analog readouts. Pilots have criticized digital displays for their inability to clearly indicate airspeed and altitude rate information. Thus, the present study also examined the utility of implementing computer-generated “Analog Dials” on the HUD to enhance recovery by providing additional cues to improve rate awareness.