A Commercial Aviation Safety Team (CAST) study of 18 loss-of-control events determined that a lack of external visual references was a contributing factor in 17 of these events. CAST recommended that manufacturers should develop and implement virtual day-VMC display systems, such as synthetic vision (SV) or equivalent systems (CAST Safety Enhancement, SE-200). In support of this recommended action, CAST has requested studies to define minimum requirements for virtual day-visual meteorological conditions (VMC) displays to improve flight crew awareness of airplane attitude. NASA’s research in Virtual day-VMC displays, known as synthetic vision systems, are intended to support intuitive flight crew attitude awareness similar to a day-VMC-like environment, especially if they could be designed to create visual dominance. A study was conducted to evaluate the utility of ambient vision (AV) cues paired with virtual Head-Up Display (HUD) symbology on a prototype head-worn display (HWD) during recovery from unusual attitudes in a simulated environment. The virtual-HUD component meets the requirement that the HWD may be used as an equivalent display to the HUD. The presence of AV cueing leverages the potential that a HWD has over the HUD for spatial disorientation prevention. The simulation study was conducted as a single-pilot operation, under realistic flight scenarios, with off-nominal events occurring that were capable of inducing unusual attitudes. Independent variables of the experiment included: 1) AV capability (on vs off) 2) AV display opaqueness (transparent vs opaque) and display location (HWD vs traditional headdown displays); AV cues were only present when the HWD was being worn by the subject pilot.
Recent accident and incident data suggest that Spatial Disorientation (SD) and Loss-of-Energy State Awareness (LESA) for transport category aircraft are becoming an increasingly prevalent safety concern in domestic and international operations. A CAST study of 18 loss-of-control accidents determined that a lack of external visual references (i.e., darkness, instrument meteorological conditions, or both) was associated with a flight crew’s loss of attitude awareness or energy state awareness in 17 of these events. In response, CAST requested that the National Aeronautics and Space Administration (NASA) conduct research to support definition of minimum requirements for Virtual Day-Visual Meteorological Condition (VMC) displays, also known as Synthetic Vision Systems, to accomplish the intended function of improving flight crew awareness of airplane attitude. These research data directly inform the development of minimum aviation system performance standards (MASPS) for RTCA special committee (SC)-213, “Enhanced Flight Vision Systems and Synthetic Vision Systems.” An overview of NASA high-fidelity simulator research is provided that collected data specific to CAST and RTCA needs on the efficacy of synthetic vision technology to aid in attitude awareness and prevent entry into, and recovery from unusual attitudes. The paper highlights our research with low-hour, international flight crews.
Head-Worn Displays (HWDs) are envisioned as a possible equivalent to a Head-Up Display (HUD) in commercial and general aviation. A simulation experiment was conducted to evaluate whether the HWD can provide an equivalent or better level of performance to a HUD in terms of unusual attitude recognition and recovery. A prototype HWD was tested with ambient vision capability which were varied (on/off) as an independent variable in the experiment testing for attitude awareness. The simulation experiment was conducted in two parts: 1) short unusual attitude recovery scenarios where the aircraft is placed in an unusual attitude and a single-pilot crew recovered the aircraft; and, 2) a two-pilot crew operating in a realistic flight environment with "off-nominal" events to induce unusual attitudes. The data showed few differences in unusual attitude recognition and recovery performance between the tested head-down, head-up, and head-worn display concepts. The presence and absence of ambient vision stimulation was inconclusive. The ergonomic influences of the head-worn display, necessary to implement the ambient vision experimentation, may have influenced the pilot ratings and acceptance of the concepts.