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.