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.
Synthetic Vision Systems and Enhanced Flight Vision System (SVS/EFVS) technologies have the potential to provide additional margins of safety for aircrew performance and enable operational improvements for low visibility operations in the terminal area environment. Simulation and flight tests were jointly sponsored by NASA’s Aviation Safety Program, Vehicle Systems Safety Technology project and the Federal Aviation Administration (FAA) to evaluate potential safety and operational benefits of SVS/EFVS technologies in low visibility Next Generation Air Transportation System (NextGen) operations. The flight tests were conducted by a team of Honeywell, Gulfstream Aerospace Corporation and NASA personnel with the goal of obtaining pilot-in-the-loop test data for flight validation, verification, and demonstration of selected SVS/EFVS operational and system-level performance capabilities.
Nine test flights were flown in Gulfstream’s G450 flight test aircraft outfitted with the SVS/EFVS technologies under low visibility instrument meteorological conditions. Evaluation pilots flew 108 approaches in low visibility weather conditions (600 feet to 3600 feet reported visibility) under different obscurants (mist, fog, drizzle fog, frozen fog) and sky cover (broken, overcast).
Flight test videos were evaluated at three different altitudes (decision altitude, 100 feet radar altitude, and touchdown) to determine the visual advantage afforded to the pilot using the EFVS/Forward-Looking InfraRed (FLIR) imagery compared to natural vision. Results indicate the EFVS provided a visual advantage of two to three times over that of the out-the-window (OTW) view. The EFVS allowed pilots to view the runway environment, specifically runway lights, before they would be able to OTW with natural vision.
NASA Langley Research Center and the FAA collaborated in an effort to evaluate the effect of Enhanced Vision (EV) technology display in a commercial flight deck during low visibility surface operations. Surface operations were simulated at the Memphis, TN (FAA identifier: KMEM) airfield during nighttime with 500 Runway Visual Range (RVR) in a high-fidelity, full-motion simulator. Ten commercial airline flight crews evaluated the efficacy of various EV display locations and parallax and minification effects. The research paper discusses qualitative and quantitative results of the simulation experiment, including the effect of EV display placement on visual attention, as measured by the use of non-obtrusive oculometry and pilot mental workload. The results demonstrated the potential of EV technology to enhance situation awareness which is dependent on the ease of access and location of the displays. Implications and future directions are discussed.
Synthetic Vision Systems and Enhanced Flight Vision System (SVS/EFVS) technologies have the potential to provide
additional margins of safety for aircrew performance and enable operational improvements for low visibility operations
in the terminal area environment with equivalent efficiency as visual operations. To meet this potential, research is
needed for effective technology development and implementation of regulatory and design guidance to support
introduction and use of SVS/EFVS advanced cockpit vision technologies in Next Generation Air Transportation System
A fixed-base pilot-in-the-loop simulation test was conducted at NASA Langley Research Center that evaluated the use
of SVS/EFVS in NextGen low visibility ground (taxi) operations and approach/landing operations. Twelve crews flew
approach and landing operations in a simulated NextGen Chicago O'Hare environment. Various scenarios tested the
potential for EFVS for operations in visibility as low as 1000 ft runway visibility range (RVR) and SVS to enable lower
decision heights (DH) than can currently be flown today. Expanding the EFVS visual segment from DH to the runway
in visibilities as low as 1000 RVR appears to be viable as touchdown performance was excellent without any workload
penalties noted for the EFVS concept tested. A lower DH to 150 ft and/or possibly reduced visibility minima by virtue of
SVS equipage appears to be viable when implemented on a Head-Up Display, but the landing data suggests further study
for head-down implementations.