Previous research has shown that the use of configural displays allows people to more easily detect changes in dynamic
processes for integration tasks thereby enhancing operator performance, yet the benefit of configural displays on
operator situation awareness (SA) has yet to be assessed. To test whether or not the use of configural displays impacts
the formation of pilot SA, a computer-based study was undertaken using two presentation rates (500ms and 1000ms)
and three configural display formats (Mil-Std-1787 HUD, Dual-articulated (DA) HUD, and the Arc Segment Attitude
Reference (ASAR)) to present aircraft flight reference information to pilots. One of five questions were possible
following the removal of the display from the screen, a query about aircraft airspeed, altitude, flight path angle (climb or
dive) or bank angle. The aim of the study was to demonstrate the ability to provide an increase in operator SA by
utilizing emergent features in configural displays to increase cue saliency and thereby increase operator SA. The
analysis of pilots' recall of aircraft flight path angle (percent correct) showed that pilots were significantly more aware
of aircraft attitude with the ASAR than with either the MIL-STD 1787 or DA HUD formats. There was no difference
among displays for recall of actual flight path angle (RMS error). The results are discussed in terms of the use of
configural displays as a design approach in representing task goals to facilitate operator SA.
A Non-Distributed Flight Reference (NDFR) symbology set intended for fixed-wing aircraft helmet-mounted display (HMD) was evaluated by the U.S. Air Force Test Pilot School (USAF TPS) Have ATTITUDE test team in March and April 2001. Revisions were made to the NDFR symbology based on the Have ATTITUDE test team's recommendations resulting in a new HMD off-boresight symbology design called the Advanced NDFR (ANDFR). The ANDFR symbology was designed to provide continuous ownship status information with more precision and trend information
over that of the original NDFR for airspeed, altitude, and attitude by utilizing odometer formats for airspeed and altitude and the arc segment attitude reference (ASAR) in place of the earlier orange peel for attitude. Three off-boresight HMD symbology sets, the ANDFR, baseline (BL) and baseline-plus (BL+) were evaluated using the NF-16D Variable-stability In-flight Simulator Test Aircraft (VISTA). Testing was performed at the USAF Flight Test Center at Edwards AFB,
California, by the Have SYCLOPS test team from the USAF TPS in March and April 2003. Two VISTA calibration and twelve VISTA test sorties totaling 19.3 flight hours were accomplished in addition to three target sorties totaling 3.5 hours. The primary objective was to assess pilot awareness of trend concerning airspeed and altitude for the BL and BL+ symbology (i.e., Mil-Std-HUD counter-pointers) compared to the ANDFR (i.e., odometers for airspeed and altitude).
Overall, the ANDFR performed equally as well as the BL and BL+ formats for the unusual attitude recoveries and air-to-air and air-to-ground operationally representative tasks. It is recommended that more testing be conducted using the ASAR design with an enhanced horizon reference (e.g., 360° horizon) off-boresight for discerning the location of the nearest horizon during steep climbs as well as an enhanced analog level flight reference for flight path angles less than 20° climb/dive. These results and their implications on the design of future off-boresight HMD symbology sets for trend and attitude awareness are discussed.
KEYWORDS: Head-mounted displays, Heads up displays, Weapons, Radar, Visualization, Control systems, Defense and security, Analog electronics, Switches, Lead
Ownship status helmet-mounted display (HMD) symbology for off-boresight use in fixed-wing tactical aircraft serves to convey aircraft state information (e.g., airspeed, heading, altitude, and attitude) to the pilot for increased situation awareness and maintenance of spatial orientation. A recent flight test evaluation of HMD symbology conducted by the Air Force Research Laboratory (AFRL) and the Edwards AFB Test Pilot School (TPS) indicated a clear performance advantage afforded by the use of off-boresight symbology compared to HUD use alone. The results indicated that the Non-Distributed Flight Reference (NDFR) was the best format of the HMD symbol sets evaluated and served as a good information/orientation aid off-boresight but needs further development to realize its tactical benefit. Specifically, the TPS recommendations pointed to a need for an improved rate-of-change (i.e., trend) indicator for airspeed and altitude, as well as an improvement to the off-boresight attitude reference concerning attitude precision (i.e., climb-dive), particularly near straight and level flight. Based on these recommendations, AFRL modified the original design of the NDFR symbology to satisfy the deficiencies noted by the Edwards AFB TPS. Two variants of the NDFR format with modifications for conveying trend information for airspeed and altitude as well as precision of aircraft attitude were evaluated along with the Mil-Std-1787D HUD symbology and baseline NDFR format. The study examined the four symbol sets during two simulated operationally representative air-to-air intercept tasks that employed the use of an HMD for the off-boresight visual acquisition of a target aircraft. Overall, the NDFR/Odometer symbology allowed a significantly higher amount of off-boresight viewing time while equaling the HUD and other off-boresight symbol sets for primary task performance and proved to be the preferred format for trend mechanization based on pilot comments.
The helmet-mounted display (HMD) will be used as the sole means of displaying head-up information to the pilot in future U.S. Air Force (USAF) fixed-wing tactical aircraft. For current fighter aircraft that employ the use of a stand-alone head-up display (HUD), the HMD will be integrated to provide the off-boresight symbology component of the head-up presentation. The symbology for on- and off-boresight use has to be designed to insure the effective interaction between display formats for conveyance of information to the pilot when transitioning between on- and off-boresight viewing angles. This is true for legacy aircraft where the symbology is presented in part by the HUD for on-boresight use with the HMD utilized for the off-boresight application and also for HUD-less aircraft, such as the Joint Strike Fighter, where symbology will be presented solely on the HMD. The Air Force Research Laboratory has been developing HMD symbology to meet the requirements to certify the HMD as a primary flight reference (PFR) for USAF fixed-wing tactical aircraft. This symbology has been designed to maximize the transference of attitude awareness to the pilot when switching between on- and off-boresight attitude references to help insure the pilot achieves correct awareness of spatial orientation. This paper describes the previous research that examined the ASAR for HUD applications, the design of the AFRL ASAR HUD symbology to replace the climb-dive ladder, and the planned flight test evaluation of the ASAR HUD for endorsement as a PFR.
Recent technological advances allow symbology to be displayed on the pilot's 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.
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.
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 study's 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.
This paper describes an evaluation of the Non-Distributed Flight Reference (NDFR) helmet-mounted display symbology for a simulated aircraft-maneuvering task. In this experiment, pilot performance concerning interpretability of three symbol sets (standard HUD, VCATS, and NDFR) during a simulated flying maneuver was assessed.
Thin membranes with curvature are investigated as mirror substrates for use in large optical telescopes. These films are mounted on an optically flat circular ring and stretched over a smaller optically flat circular ring where pressure or vacuum is applied to create the doubly curved surface as shown in figure 1. The films may vary in thickness from 20 to 200 microns. This particular experiment examines an aluminum coated 125 micron thick homogeneous, planar, isotropic membrane with a clear aperture of 28 centimeters. The nature of a flexible membrane implies that the surface curvature will result in an assorted array of gross surface figure issues associated with deterministic shape limits, probabilistic imperfections, nonlinear constitutive effects, and long-time- dependent effects. This report will focus on the empirical deterministic shape limits of a doubly curved membrane. Theoretical work on thin films inflated or evacuated into a doubly curved surface has a long history, and remains an active area of research. A number of articles [1,2,3,4,7] include summaries of this history, and offer insight on the deterministic membrane shapes.
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