Eric E. Geiselman

Flight test evaluation of the nondistributed flight reference off-boresight helmet-mounted display symbology

The Air Force Research Laboratory (AFRL) has been working to optimize helmet-mounted display (HMD) symbology for off-boresight use. One candidate symbology is called the non-distributed flight reference (NDFR). NDFR symbology allows ownship status information to be directly referenced from the HMD regardless of pilot line of sight. The symbology is designed to aid pilot maintenance of aircraft state awareness during the performance of off-boresight tasks such as air-to-ground and air-to-air target acquisition. Previous HMD symbology research has shown that pilots spend longer periods of time off-boresight when using an HMD and therefore less time referencing primary displays in the aircraft cockpit. NDFR may provide needed information for the pilot to safely spend longer periods of search time off-boresight. Recently, NDFR was flight tested by the USAF Test Pilot School at Edwards AFB, CA, aboard the VISTA F-16 (Variable Stability In-flight Simulator Test Aircraft) during operationally representative air-to-air and air-to-ground tasks, as well as unusual attitude recoveries. The Mil-Std-1787B head-up display (HUD) symbology and another off-boresight HMD symbology called the Visually Coupled Acquisition and Targeting System (VCATS) were evaluated as comparison symbol sets. The results of the flight test indicate a clear performance advantage afforded by the use of off-boresight symbology compared to HUD use alone. There was a significant increase in the amount of time pilots looked off-boresight with both the NDFR and VCATS symbologies. With the NDFR, this increase was achieved without an associated primary task performance tradeoff. This was true for both air-to-ground and air-to-air tasks.

Utility of off-boresight helmet-mounted symbology during a high-angle airborne target acquisition task

This experiment compares the utility of three off-boresight helmet-mounted display (HMD) symbology information levels for high angle target search and intercept during a simulated air-to-air engagement. The information levels included: Head-Up Display (HUD) presentation of both ownship status and target location, HUD status plus HMD target location, and HUD status plus HMD target location plus HMD ownship status. Four different attitude symbology elements were evaluated within ownship status level. The levels of the information condition variable evolved from the following questions: 1) Will HMD ownship status information help the pilot fly while searching for threats? 2) Will HMD target location information help the pilot find, intercept, and track an airborne target? 3) What is the effect of combining aircraft status and target location information within the HMD? 4) If ownship status information is helpful, are there symbology features which are more interpretable than others? The objective of this research was to determine of ownship status information within the helmet display symbology (HDS) set is necessary in an air-to-air application. The findings suggest that HDS will be advantageous, but task dependent. A strong subjective preference for including ownship status information within the HDS was found.

Helmet-display resident target locator line symbology: an evaluation of vector length depiction

The helmet resident locator line with a look-to orientation is designed to guide the users line- of-sight (LOS) to a specific point-of-interest (POI) in space. The locator line is used to indicate the relative position of a POI within the sensor field-of-regard but beyond the display field-of- view (FOV). The distance the LOS must traverse in order to bring the POI within the display FOV is called vector length. The present study was conducted to investigate the effects of different locator line vector length symbology approaches on search and tracking performance. Five candidate symbologies were formed by varying their static and dynamic features. The locator lines were compared using both static interpretation and dynamic tracking tasks. Recommendations for the use of specific symbology features are made.

Rise of the HMD: the need to review our human factors guidelines

Recent years have brought on a new breed of HMDs. They have high resolution, are daylight readable, and some even have color. While these are all welcomed advances to the field we must remember to review our history. Here we review some the of the research from years past that was done before these advances and discuss them so as to make sure the past is not forgotten and mistakes are not repeated.

A Comparison of HMD Ownship Status Symbology and Frame of Reference Orientation During Two Aircraft Control Tasks

Recent technological advances allow symbology to be displayed on the pilots visor. A major benefit of this is that the pilot will be able to take this information with them when they look off-boresight. However, when looking off-boresight the question arises as to what is the best orientation, or frame of reference, for attitude symbology against the horizon (i.e., forward or line-of-sight) in order to maximize interpretation and performance. This study tested five different symbologies (standard HUD, visually coupled acquisition and targeting symbology, arc segmented attitude reference, theta ball, and non-distributed flight reference) of which three have both forward and line-of-sight orientations. The experiment consisted of two different tasks, with the pilots performing either facing the monitor or rotated 90 degree(s) and looking over their shoulder (off-boresight). In the first task, pilots maintained straight and level flight with simulated turbulence. The second task had pilots interpret a static representation of their attitude and respond via a key press, and then the display went live and they had to fly to a new commanded attitude. This second task was similar to a recovery from unusual attitude methodology, except the end state was never straight and level. Instead, a second unknown end state attitude was commanded by the experiment. Results indicate that performance is better when the symbology is forward as opposed to line-of-sight referenced. Further, performance was best in both tasks for the non-distributed flight reference. We discuss these results in terms of implications for helmet-mounted display symbology design.

Toward an Empirically Based Helmet-Mounted Display Symbology Set

The helmet-mounted display (HMD) affords continuous availability of critical flight information independent of head orientation. With appropriate information presented on a HMD, aircraft control can be maintained regardless of where the pilot is looking. This research addresses the development of an empirically based HMD symbol set. Three attitude formats and three altitude formats were evaluated within a composite fixed-wing HMD symbology layout. The attitude formats varied in basic form and symbol compression ratio. Symbol compression ratio is the ratio of the angle represented by the symbol to the symbols subtended visual angle. High symbol compression results in symbols which represent large angles, and therefore have slow rate-of-motion relative to their uncompressed counterparts. The altitude symbologies were formed of both vertical scale and dial formats and included vertical velocity indicators. Subjects performed a flight-path maintenance task within sessions of differing “real” horizon presence and orientation. The formats were evaluated under a task which was designed to require high-accuracy flight-path maintenance. This type of task is traditionally thought to require less symbol compression. The results showed that performance was influenced by the manipulation of the attitude symbology formats. The results also suggest that symbol compression may be advantageous.

Evaluation of off-boresight helmet-mounted display symbology formats for interpretation of ownship status information

Three variations of the non-distributed flight reference (NDFR) off-boresight helmet-mounted display (HMD) symbology were evaluated along with the Mil-Std-1787C HUD symbology and an off-boresight HMD symbology called the Visually Coupled Acquisition and Targeting System (VCATS), for interpretation of ownship status information. Using twenty predetermined flight path segments lasting 3 to 5 seconds each, the NDFR, NDFR plus climb-dive angle reference, mini-arc NDFR, Standard HUD, and VCATS symbologies were compared for recall of ownship status information. Twelve military or civilian rated pilots participated. Pilots viewed all five symbology formats with ownship status information recalled at the end of each flight path. Pilots provided feedback of ownship status using a free recall methodology. Mil-Std-1787C HUD served as the baseline measure of comparison with the primary comparison of interest being the off-boresight HMD symbology formats. The studys aim was to evaluate the baseline NDFR format along with alternate symbology designs to arrive at an HMD symbology for off-boresight applications that is highly usable in terms of awareness of aircraft state and orientation. The results of the study showed that, although no single NDFR format proved best for all information categories, taken as a group, the NDFR symbology proved to be the preferred symbology format for the information categories investigated. The NDFR format equaled recall performance for Standard HUD and outperformed or equaled the VCATS off-boresight symbology. Further evaluation of the NDFR concept is planned using pilot-in-the-loop HMD simulations evaluating modifications to the NDFR for trend information and attitude determination and investigating display compatibility with the virtual HUD concept.

A Comparison of Three Attitude Display Symbology Structures during an Attitude Maintenance Task

The present study evaluated a new aircraft attitude display concept. The new symbology format, or Theta display, was developed by integrating the features of the conventional attitude/direction indicator (ADI) and head-up attitude reference display (HUD) into a single format. Number of trials to reach a specific performance criterion and tracking performance were collected as dependent variables on an attitude maintenance task. The results show that performance and training time were better with both the Theta display and the ADI than with the HUD. The findings support the hypothesis that an attitude display formed of the integration of ADI and HUD symbology will demonstrate a performance benefit over a pure HUD format.

Making the case for off-axis ownship attitude symbology: we may not miss it until it's not there

There has been significant research completed attempting to optimize the portrayal of ownship attitude information (OAI) via the Helmet-Mounted Display and, there has simultaneously been resistance by the user community regarding the inclusion of OAI. The stated reason is usually because they find it unnecessary. This paper includes a review of both sides of this discussion and attempts to make the case that, similar to the evolution of the Head-Up Display as a primary flight reference, there are likely operational performance and safety-of-flight reasons to justify off-axis OAI within even limited field-of-view applications.

How much camera separation should be used for the capture and presentation of 3D stereoscopic imagery on binocular HMDs

Designers, researchers, and users of binocular stereoscopic head- or helmet-mounted displays (HMDs) face the tricky issue of what imagery to present in their particular displays, and how to do so effectively. Stereoscopic imagery must often be created in-house with a 3D graphics program or from within a 3D virtual environment, or stereoscopic photos/videos must be carefully captured, perhaps for relaying to an operator in a teleoperative system. In such situations, the question arises as to what camera separation (real or virtual) is appropriate or desirable for end-users and operators. We review some of the relevant literature regarding the question of stereo pair camera separation using deskmounted or larger scale stereoscopic displays, and employ our findings to potential HMD applications, including command & control, teleoperation, information and scientific visualization, and entertainment.