Patrizia Knabl

Designing an obstacle display for helicopter operations in degraded visual environment

Flying in degraded visual environment is an extremely challenging task for a helicopter pilot. The loss of the outside visual reference causes impaired situation awareness, high workload and spatial disorientation leading to incidents like obstacle or ground hits. DLR is working on identifying ways to reduce this problem by providing the pilot with additional information from fused sensor data. Therefore, different display design solutions were developed. In a first study, the design focused on the use of a synthetic head-down display, considering different representations for obstacles, color coding and terrain features. Results show a subjective preference for the most detailed obstacle display, while objective results reveal better performance for the little less detailed display. In a second study, symbology for a helmet-mounted display was designed and evaluated in a part-task simulation. Design considerations focused on different obstacle representations as well as attentional and perceptual aspects associated with the use of helmet-mounted displays. Results show consistent findings to the first experiment, indicating that the display subjectively favored does not necessarily contribute to the best performance in detection. However when additional tasks have to be performed the level of clutter seems to impair the ability to respond correctly to secondary tasks. Thus the favored display type nonetheless seems to be the most promising solution since it is accompanied by the overall best objective results integrating both detection of obstacles and the ability to perform additional tasks.

Developing an obstacle display for helicopter brownout situations

Project ALLFlight is DLRs initiative to diminish the problem of piloting helicopters in degraded visual conditions. The problem arises whenever dust or snow is stirred up during landing (brownout/whiteout), eectively blocking the crews vision of the landing site. A possible solution comprises the use of sensors that are able to look through the dust cloud. As part of the project display symbologies are being developed to enable the pilot to make use of the rather abstract and noisy sensor data. In a rst stage sensor data from very dierent sensors is fused. This step contains a classication of points into ground points and obstacle points. In a second step the result is augmented with ground data bases and depicted in a synthetic head-down display. Regarding the design, several variations in symbology are considered, including variations in color coding, continuous or non-continuous terrain displays and dierent obstacle representations. In this paper we present the basic techniques used for obstacle and ground separation. We choose a set of possibilities for the pilot display and detail the implementation. Furthermore, we present a pilot study, including human factors assessment with focus on usability and pilot acceptance.

An evaluation environment for a helmet-mounted synthetic degraded visual environment display

Degraded visual environment (DVE) is a term coined for environmental conditions that impair the visual orientation of a helicopter pilot during flight or landing. These conditions include brown-out, but also night, glare, fog and mist, as well as combinations of those. In order to assist pilots under DVE conditions DLR, the German Aerospace Center, initiated project ALLFlight. Using a combination of multi-sensor fusion, specialized symbologies for head-down and helmet-mounted display, and database augmentation the pilot should be enabled to safely operate the helicopter. Based on an earlier implementation of a synthetic head-down display an implementation for a head-tracked, helmet-mounted system is implemented. Since color is presently not an option for head-up displays, alternative symbologies have to be considered, including variations in transparency, density of terrain displays and size and shape variations for obstacle representation. In this paper we present a simulator setup for evaluating the display concepts developed. This includes various simulation stages for visual and sensor input and a flexible simulator cockpit for testing variations of display concepts. We detail the implementation architecture and present first evaluation details from a recent pilot study.

Symbology development for a 3D conformal synthetic vision helmet-mounted display for helicopter operations in degraded visual environment

To increase situation awareness for helicopter pilots in poor visibility symbology for a helmet-mounted display was developed. The symbology comprises the conformal presentation of obstacles, route information and threat areas. In an online survey 48 helicopter pilots evaluated the designs from a user-centered perspective and provided comments and suggestions of improvement. The paper presents selected results of the survey and discusses general aspects associated with the use of conformal symbology and helmet-mounted displays.

Design considerations for a helmet-mounted synthetic degraded visual environment display

Piloting helicopters in degraded visual environments (DVE) remains one of the major challenges for the next years. While some research concentrated on the specialized problem of brownout landing, low visibility conditions in general cover a broader range of scenarios that further includes night, glare, fog and mist, as well as combinations of those. Project ALLFlight is DLRs initiative to diminish the problems of piloting helicopters under such circumstances. A possible solution comprises the use of sensors that are able to sense the environment even if the pilot cannot effectively see anything. As part of the project display symbologies are being developed to enable the pilot to make use of the rather abstract and noisy sensor data. In a first stage sensor data from very different sensors is fused. This step contains a classification of points into ground points and obstacle points. In a second step the result is augmented with ground data bases. Based on an earlier implementation of a synthetic head-down display an implementation for a head-tracked, helmet-mounted system is being developed. Since color is presently not yet an option for head-up displays, alternative symbologies have to be considered, including variations in transparency, density of terrain displays and size and shape variations for obstacle representation. In this paper we present the basic techniques used for obstacle and ground separation. We choose a set of possibilities for the pilot display and detail the implementation.

Amplifying the helicopter drift in a conformal HMD

Helicopter operations require a well-controlled and minimal lateral drift shortly before ground contact. Any lateral speed exceeding this small threshold can cause a dangerous momentum around the roll axis, which may cause a total roll over of the helicopter. As long as pilots can observe visual cues from the ground, they are able to easily control the helicopter drift. But whenever natural vision is reduced or even obscured, e.g. due to night, fog, or dust, this controllability diminishes. Therefore helicopter operators could benefit from some type of “drift indication” that mitigates the influence of a degraded visual environment. Generally humans derive ego motion by the perceived environmental object flow. The visual cues perceived are located close to the helicopter, therefore even small movements can be recognized. This fact was used to investigate a modified drift indication. To enhance the perception of ego motion in a conformal HMD symbol set the measured movement was used to generate a pattern motion in the forward field of view close or on the landing pad. The paper will discuss the method of amplified ego motion drift indication. Aspects concerning impact factors like visualization type, location, gain and more will be addressed. Further conclusions from previous studies, a high fidelity experiment and a part task experiment, will be provided. A part task study will be presented that compared different amplified drift indications against a predictor. 24 participants, 15 holding a fixed wing license and 4 helicopter pilots, had to perform a dual task on a virtual reality headset. A simplified control model was used to steer a “helicopter” down to a landing pad while acknowledging randomly placed characters.

Onboard radar display for VFR collision avoidance

In VFR (visual flight rules) situations the pilot is responsible for collision avoidance. This can be problematic in case of high-speed business jets entering the vicinity of a local airport. Often, this airspace is occupied by slow, low-visibility aircraft like gliders, ultralight vehicles or, occasionally, balloons. These may be not equipped with active transponders. Thus, it is up to the pilot of the jet to take care of see-and-avoid separation.