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Visual Display Design for Mitigation of Helicopter and Tiltrotor Brownout Spatial Disorientation


OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)


TECHNOLOGY AREA(S): Air Platforms;Human Systems


OBJECTIVE: Design, build, and demonstrate a vertical lift platform (i.e., helicopter or tiltrotor) cockpit visual display that mitigates spatial disorientation during brownout landings and takeoffs. The display must be compatible with DoD vertical lift/aircrew systems currently in use.


DESCRIPTION: The term “brownout” refers to degradation of out-the-window cockpit visibility during landings or takeoffs from areas with loose, dry, ground soil. During brownouts, loss of visibility occurs when a helicopter or tiltrotor’s main rotor blades stir up dirt, dust, or sand, which is then re-circulated through the blades and over the windscreen during low ground hover operations. The Joint Air Power Competence Centre (JAPCC) reported that the most dangerous action a helicopter pilot can take is land in brownout conditions. Additionally, it cited a USAF Institute of Technology report which states that the U.S. Department of Defense (DoD) had over 100 million USD in costs attributed to brownout mishaps. Furthermore, 65% of non-hostile fatalities have been from brownout hover and low speed flight. A final conclusion from the JAPCC’s report was that while many phases of helicopter flight can be performed with only instrument scanning, landing and hovering cannot [Ref 1].


During vertical hover landings or takeoffs with good outside visibility, rotary-wing and tiltrotor pilots maintain spatial orientation by using two types of outside visual cues. The first is a distant view of a horizontal reference that can be used for detecting unintended roll or pitch motions, and the second is a view of nearby fixed ground objects used as references for detecting unintended yaw, side drift, or forward and aft motion. With Visual Meteorological Conditions (VMC), primary spatial cues for rotary-wing and tiltrotor pilots are defined as fixed foveal views of distant (horizon) or near (ground) references. In contrast, secondary spatial cues have been defined as unstabilized peripherally viewed objects (such as cockpit components or outside airframe structures) that are perceived as being in motion as they change retinal position relative to the stabilized primary cue. Together, fixed primary and moving secondary spatial cues create a dynamic sight picture that allows pilots to use a VMC spatial strategy for determining aircraft attitude and directional rate of movement [Ref 2]. If visibility of either primary cue type is blocked by circulating particles within the rotor blade vortex ring, the pilot will suffer an immediate loss of critical spatial information, which unfortunately, also creates a high potential for spatial disorientation (SD) and incorrect control inputs.


When brownouts cause pilots to suddenly lose their outside visual cues seconds before touchdown, they are forced instantly to decide whether to attempt a rapid instrument transition or continue with an outside scan, hoping to see a visual ground reference seconds before setting down. Unfortunately, when transitioning from an outside view to head down instruments, the Federal Aviation Administration (FAA) has documented that establishing full instrument control after the loss of surface visual reference can take as much as 35 seconds [Ref 3]. With brownout conditions, sudden loss of the primary spatial cues (horizon and ground) and the limited time available to successfully transition to instruments, creates a high risk for SD.


Researchers have demonstrated that pilots exhibit specific reflexive head and eye movements that influence sight picture dynamics in a manner that aids with development of VMC spatial strategies [Refs 2, 4, and 5]. Brownout visual countermeasures that accommodate these normal pilot behaviors may help reduce pilot spatial problems known to occur with less than optimum display designs. To mitigate this risk, the DoD is seeking a non-energy signature emitting visual display system with a presentation that will mimic pilot outside spatial strategies when encountering degraded visual environments (DVE).


Proposed display designs should enable a seamless transition time between real-world spatial cues and display symbology and consideration should be given for incorporation of flight path predictor type symbology. Design proposals should also describe, in general terms, compatibility with existing rotary-wing and tiltrotor systems such as (but not limited to): weight issues, cost estimate assessment, display transition time, and usability with both day and night conditions.


The prototype display should be constructed in a manner compatible with both stationary (non-motion) flight simulator and a motion-based flight simulator with six degrees of freedom (6DOF). The first stage of the evaluation should involve non-motion flight simulation with brownout conditions and the second stage should repeat stage one in a simulated flight environment with full 6DOF motion. Since the combined motion and visual environments of rotary-wing and tiltrotor brownout usually involve 6DOF, the Navy Disorientation Research Device (DRD) at the Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Ohio, may be considered as a potential test facility for Phases II and III efforts. It is expected that a fully operational and complete (hardware and software) brownout mitigation visual display prototype will not require input from airframe emitted sensory energy and will operate using open-source software that is compatible with desktop Microsoft CPU systems. Device prototype and test subject raw performance data collected in ASCII format during test and evaluation with motion and non-motion based brownout simulations. Phase II final report that contains a detailed schematic and a complete description for operation of the brownout mitigation visual display system. The final report should also include a detailed analysis of the performance testing data collected during motion and non-motion brownout simulations.


Test and evaluation should demonstrate the prototype display capability for preventing SD during sudden and unexpected encounters with brownout conditions during high workload conditions. The experimental design for evaluating the working prototype should include DoD rotary-wing and tiltrotor pilots as test subjects and have a statistical power of 0.80 or higher. Dependent variables for display assessment should include, but not be limited to, pilot landing and takeoff tracking performance (roll, pitch, yaw, ascent, descent, airspeed, and drift), Opto-Kinetic Cervical Reflex (OKCR) response, eye tracking, Control Reversal Errors (CRE), subjective workload assessment, and motion sickness susceptibility.


Note: NAVAIR will provide Phase I performers with the appropriate guidance required for human research protocols so that they have the information to use while preparing their Initial Phase II Proposal. Institutional Review Board (IRB) determination as well as processing, submission, and review of all paperwork required for human subject use can be a lengthy process. As such, no human research will be allowed until Phase II and work will not be authorized until approval has been obtained, typically as an option to be exercised during Phase II.


PHASE I: Develop, describe, and define potential methodologies and designs for a visual display system that will prevent loss of spatial awareness during DVE encountered with brownout conditions. During the Phase I process, plans for designing an optimum visual countermeasure for brownout should take into consideration the types of cognitive processing pilots use with inflight spatial strategies, during both VMC and Instrument Meteorological Conditions (IMC). Provide detailed Phase I final report that includes concepts and plans to develop and test a brownout mitigation visual display for rotary-wing aircraft in stationary and 6DOF simulators. The Phase I effort will include prototype plans to be developed under Phase II.


Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.


PHASE II: Develop a working prototype visual display for mitigating or eliminating pilot SD during brownout takeoffs and landings.


Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.


PHASE III DUAL USE APPLICATIONS: Integrate display design into a 6DOF motion simulator and vertical lift platform. Final end user testing, validation, and verification of the display system in DVE conditions.


Private sector or corporate transportation services that utilize vertical lift platforms (i.e., helicopters) can experience degraded visual environments due to unexpected weather conditions or terrain challenges. These conditions can lead to mishaps due to resulting spatial disorientation. In addition, federal (e.g., USCG, DHS, FBI), state (National Guard units, Civil Air Patrol), or local (e.g., Firefighter/Paramedics, life flight) government search and rescue that utilize vertical lift platforms may benefit from the use of an advanced display design to mitigate spatial disorientation associated with DVE conditions. A secondary application may be in the display system used with unmanned aerial systems with vertical lift capabilities.



  1. Modesto, M. (2017). “Beating brownout: Technology helps, but training remains key.” Joint Air Power Competence Centre.
  2. Patterson, F. R., Cacioppo, A. J., Gallimore, J. J., Hinman, G. E., & Nalepka, J. P. (1997). “Aviation spatial orientation in relationship to head position and attitude interpretation.” Aviation, Space, and Environmental Medicine, 68(6), 463–471.
  3. Hunt, K. S. (1983, February 9). “Advisory circular: Pilot’s spatial disorientation.” AC No. 60-4A. Federal Aviation Administration.
  4. Patterson, F. R., & Muth, E. R. (2010, September 9). “Cybersickness onset with reflexive head movements during land and shipboard head-mounted display flight simulation, Report Number 10-43.” Naval Aerospace Medical Research Laboratory.
  5. Moore, S. T., MacDougall, H. G., Lesceu, X., Speyer, J. J., Wuyts, F., & Clark, J. B. (2008). “Head-eye coordination during simulated orbiter landing.” Aviation, Space, and Environmental Medicine, 79(9), 888-898.
  6. Naval Medical Research Unit Dayton. (n.d.). “Disorientation research device: The Kraken(TM).” Retrieved March 24, 2021, from


KEYWORDS: Degraded visual environment; DVE; future vertical lift; spatial disorientation; display symbology; display design; human factors

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