Trends in spatial disorientation research.

Trends in spatial disorientation (SD) research over the past six decades were assessed by means of a literature review using four databases and three SD-related search terms. 347 SD-related papers were identified, 37% of which were in three categories: attitude displays, SD training, and SD incidence. The most dramatic trend was a marked upswing in SD research in the 1990's.

Effect of "inside-out" and "outside-in" attitude displays on off-axis tracking in pilots and nonpilots.

BACKGROUND: Pilots employing helmet-mounted displays spend sustained periods of time looking off-axis, necessitating the inclusion of attitude symbology on the helmet to maintain spatial awareness. We examined how fundamentally different attitude references, a moving-horizon ("inside-out") or a moving-aircraft ("outside-in"), affected pilot and nonpilot attitude control when looking on- or off-axis. Both a rear-view and a side-view outside-in perspective were depicted to investigate the effect of control-display compatibility. METHODS: Subjects performed a compensatory pitch-roll tracking task either looking on-axis or 90 degrees off-axis using three symbologies: 1) a compressed pitch ladder with horizon line; 2) a 3-D aircraft representation viewed from the rear; and 3) a 3-D aircraft representation viewed from the side. Tracking error in roll and pitch, control bias, and subjective ratings were collected and analyzed. RESULTS: There was no significant difference in the tracking performance of U.S. Air Force pilots in pitch and roll using the inside-out or outside-in rear-view formats on- and off-axis, although they preferred the inside-out format. Nonpilots tracked significantly better using the outside-in rear-view format, which they also preferred. Both groups tracked poorly using the outside-in side-view format and control-display compatibility had no important effect. CONCLUSIONS: Pilots are equally adept using outside-in and inside-out displays. Given that an outside-in display may better reflect a person's inherent frame of reference for orientation (as evidenced by the nonpilots' superior performance with it), the results seem to indicate that pilots, through experience, have adapted to an inside-out frame of reference.

Post-roll effects on attitude perception: "the Gillingham Illusion".

BACKGROUND: Several aircraft each year are lost because of an unexplained collision with the ground. The attitude of most of these aircraft prior to impact was nose-low and with excessive bank, i.e., greater than 90 degrees . Prior to these accidents, each aircraft was noted as either changing heading or making an abrupt roll. HYPOTHESIS: Could there be some underlying tendency for the pilot to make unnoticed stick inputs after completing a roll from one bank angle to another? METHODS: Since ground-based flight simulators cannot create the true sensation of rolling an aircraft from one side to the other, the instrumented CALSPAN NT-33 aircraft was used for this study. Six pilots were given a series of three roll rates and two head positions while the aircraft automatically changed bank from 45 degrees of bank in one direction to 45 degrees of bank in the opposite direction. The subject's view of the external visual scene was restricted with a blue-amber vision restricting transparency combination. All attitude-indicating instruments were blanked, requiring the subjects to make stick inputs based on their vestibular (somatosensory) feedback. RESULTS: Subjects experienced a consistent tendency to increase bank angle after given control of the aircraft immediately following the roll maneuver, while thinking they were maintaining a constant bank angle. In some cases, the pilots rolled the aircraft completely inverted. CONCLUSION: When pilots rely on their perception of bank, following a roll, they will inadvertently increase their bank in the direction of the previous roll.

In defense of traditional views of spatial disorientation and loss of situation awareness: a reply to Navathe and Singh's "An operational definition of spatial disorientation".

In a recent article in Aviation, Space, and Environmental Medicine, Navathe and Singh proposed new "operational" definitions for spatial disorientation (SD) and loss of situation(al) awareness (LSA). The major feature of their new scheme was to treat the two phenomena as distinct, with SD attributable to physiologically based (peripheral) illusions and LSA to psychological (central) factors. The present commentary argues in favor of traditional views of SD that consider spatial orientation to be a subset of overall situation awareness.

United States Air Force head-up display control and performance symbology evaluations.

The United States Air Force has conducted an extensive research effort to determine the most effective way to present aircraft control, performance, and navigation information on the head-up display (HUD). The primary objective of the research was to develop a standard HUD symbology set to be used as a primary flight reference for fighter-type aircraft during instrument meteorological conditions. This paper summarizes the research conducted by scientists in the Visual Orientation Laboratory at the Flight Motion Effects Branch of the Human Systems Center's Armstrong Laboratory. Five experiments that examined various control and performance symbology elements are reviewed. Suggested standardization guidelines based on experimental findings are discussed, including the following: the use of counter-pointers for airspeed and altitude indicators, vertical and horizontal asymmetry for climb/dive ladder configurations, a ghost horizon, analog vertical-velocity information, energy management symbology, and quickening for climb/dive markers.

Classification problems of U.S. Air Force spatial disorientation accidents, 1989-91.

Spatial disorientation (SD) continues to contribute to a fairly constant proportion of military aircraft accidents. The U.S. Air Force (USAF) fielded a new accident investigation reporting form in July 1989, which for the first time specified Type I SD, Type II SD, and Type III SD as possible causes of aircraft accidents. Of a total of 91 major accidents that occurred over the 2-year period beginning in October 1989, SD was rated as contributing significantly to 13 (14%). Coding for SD on accident investigation reporting forms was not consistent, however. Individual flight surgeons differed in their approaches to coding accidents as SD-related; other differences were noted between flight surgeons and pilots, and additional procedural differences resulted in inconsistent reporting over time. There is a consensus that SD represents a major problem in military aviation, but a scientific approach to this important problem would be facilitated if agreement could be reached on definitional and semantic issues.

The effects of acoustic orientation cues on instrument flight performance in a flight simulator.

An initial version of an acoustic orientation instrument (AOI), in which airspeed was displayed as sound frequency, vertical velocity as amplitude modulation rate, and bank angle as right-left lateralization, was evaluated in a T-40 (Link GAT-3) motion-based simulator. In this study, 15 pilots and 3 non-pilots were taught to use the AOI and flew simulated flight profiles under conditions of neither visual nor auditory instrumentation (NO INPUT), AOI signals only (AOI), T-40 simulator instrumentation only (VISUAL), and T-40 simulator instrumentation with AOI signals (BOTH). Bank control under AOI conditions was significantly better than under the NO INPUT condition for all flying tasks. Bank control under VISUAL conditions was significantly better than under the AOI condition only during turning and when performing certain complex secondary tasks. The pilots' ability to use the AOI to control vertical velocity and airspeed was less apparent. However, during straight-and-level flight, turns, and descents the AOI provided the pilots with sufficient information to maintain controlled flight. Factors of potential importance in using sound to convey aircraft attitude and motion information are discussed.