Pathway-in-the-sky displays enable pilots to accurately fly difficult trajectories. However, these displays may drive pilots' attention to the aircraft guidance task at the expense of other tasks particularly when the pathway display is located head-down. A pathway HUD may be a viable solution to overcome this disadvantage. Moreover, the pathway may mitigate the perceptual segregation between the static near domain and the dynamic far domain and hence, may improve attention switching between both sources. In order to more comprehensively overcome the perceptual near-to-far domain disconnect alphanumeric symbols could be attached to the pathway leading to a HUD design concept called 'scene-linking'. Two studies are presented that investigated this concept. The first study used a simplified laboratory flight experiment. Pilots (N=14) flew a curved trajectory through mountainous terrain and had to detect display events (discrete changes in a command speed indicator to be matched with current speed) and outside scene events (hostile SAM station on ground). The speed indicators were presented in superposition to the scenery either in fixed position or scene-linked to the pathway. Outside scene event detection was found improved with scene linking, however, flight-path tracking was markedly deteriorated. In the second study a scene-linked pathway concept was implemented on a monocular retinal scanning HMD and tested in real flights on a Do228 involving 5 test pilots. The flight test mainly focused at usability issues of the display in combination with an optical head tracker. Visual and instrument departure and approach tasks were evaluated comparing HMD navigation with standard instrument or terrestrial navigation. The study revealed limitations of the HMD regarding its see-through capability, field of view, weight and wearing comfort that showed to have a strong influence on pilot acceptance rather than rebutting the approach of the display concept as such.
During approach and landing the pilot performs a high-workload task of switching the attention between instrument in-formation and the outside scene. Superimposing both visual domains in head-up (HUD) or head-mounted displays (HMD) reduces the visual scanning load of this task. These displays are collimated at optical infinity; therefore, prevent the pilot's eye from permanent accommodation between both visual domains. Besides these performance benefits, visual clutter and attention fixation, i.e. inattentiveness to outside scene events while attending on HUD symbologies, are found to be performance cost factors. Conformal symbology and flight-phase adapted de-cluttering has been found to be prom-ising approaches to overcome these problems.
In pursuit of these two approaches, the current paper describes the design of a new pathway display on a monocular head-mounted retinal scanning display and its implementation in DLR's generic cockpit simulator. The pathway can be regarded as a means of linking an instrument symbology (the tunnel) with a virtual element of the outside scene (the in-tended flight path). Scene-linked symbology appear to be part of the outside world, e.g. an instrument reading like air-speed, heading, or altitude that is changing its display location conformal with the gate element of the tunnel symbology moving towards the pilot. Examples of flight phase-adaptive de-cluttering is to successively reduce or remove symbol-ogy when the conformal outside element becomes visible (e.g. the runway). In addition the display includes a conformal presentation of the terrain. A checker board pattern representing the terrain is dynamically generated from worldwide available SRTM-3 data.
Head-up displays (HUD) and helmet (or head)-mounted displays (HMD) aim at reducing the pilot's visual scanning cost in support of concurrent monitoring of both instrument information (near domain) and the outside environment (far domain). An HMD used in combination with a head tracker enables the assessment of the pilot’s head direction in real time allowing symbologies to remain spatially linked to elements of the outside environment. The paper examines the potential added benefits of improved flight path tracking to be expected by displaying symbologies of a virtual 3D perspective pathway plus predictor information on an HMD. Results of a high-fidelity flight-simulation experiment are reported that involved a series of curved approaches supported with such a pathway HMD. The study used a monocular retinal-scanning HMD and involved 18 pilots. Dependent human performance data were derived from flight path tracking measures, subjective measures of mental workload and situation awareness and pilot reactions in response to an unexpected rare event in the outside scene (intruding aircraft on the active runway for the intended landing). Comparison with a standard head-down ILS baseline condition revealed a mix of performance costs and benefits, which is consistent with most of the human factors literature on the general use of HUDs and of HUDs used in combination with pathway guidance: The pathway HMD promoted substantially better flight path tracking but caused also a delayed response to the unexpected event. This effect points to some disadvantages of HUDs referred to as 'attention capture', which may become exaggerated by the additional use of pathway guidance symbology.
Up to now most Enhanced Vision Systems have been based on IR-sensors. Although the penetration of bad weather (dense fog and light rain) by MMW-radar is remarkably better than in the infrared spectrum MMW sensors still have the disadvantage that radar data are often difficult to interpret. Therefore, it's not always possible for the pilot to obtain a reliable detection of runway structures within the radar images. However, prior field tests have shown that the installation of two different types of radar retro-reflectors along the runway can ease the image analysis task significantly and can provide the visual cues necessary to perform precision straight-in landings. A set of corner reflectors has proven suitable to mark the runway edges needed to adjust for lateral deviations and a set of diplane reflectors provided cues to maintain a 3-degree glide path descend.
The present study obtains first objective human performance data to examine the question how efficient pilots are in utilizing these visual cues. The study tested seven VFR and seven IFR-rated pilots and used a low-fidelity human-in-the-loop visual tracking task to simulate a straight-in landing. Pilots were required to detect the lateral and vertical tracking error based on the intensity-coded visual cues provided by the simulated radar images. The study compares two display conditions derived from different spatial arrangements of the diplane reflectors that signal the glide path angles. The first, the so-called "Radar-PAPI", was a horizontal row arrangement of four diplanes, and the second, the "Radar VASI", was a two-over-two arrangement of four diplanes. A third condition simulated the existing visual color coded PAPI landing aid and served as a baseline reference. Performance evaluation was based on the calculation of the root-mean-square error for both axis and subjective preference statements of the pilots.
Enhanced Vision Systems (EVS) are currently developed with the goal to alleviate restrictions in airspace and airport capacity in low visibility conditions. Existing EVS-systems are based on IR-sensors although the penetration of bad weather (dense fog and light rain) by MMW-radar is remarkably better than in the infrared spectrum. But the quality of MMW radar is rather poor compared to IR images. However, the analysis of radar images can be simplified dramatically when simple passive radar retro-reflectors are used to mark the runway. This presentation is the third in a series of studies investigating the use of such simple landing aids. In the first study the feasibility of the radar PAPI concept was determined; the second one provided first promising human performance results in a low-fidelity simulation. The present study examined pilot performance, workload, situation awareness, and crew coordination issues in a high-fidelity simulation of 'Radar-PAPI' visual aids supporting a precision straight-in landing in low visibility (CAT-II). Simulation scenarios were completed in a fixed-base cockpit simulator involving six two-pilot flight-deck crews. Pilots could derive visual cues to correct lateral glide-path deviations from 13 pairs of runway-marking corner reflectors. Vertical deviations were indicated by a set of six diplane reflectors using intensity-coding to provide the PAPI categories needed for the correction of vertical deviations.
The study compared three display formats and associated crew coordination issues: (1) PF views a head-down B-scope display and switches to visual landing upon PNF's call-out that runway is in sight; (2) PF views a head-down C-scope display and switches to visual landing upon PNF's call-out that runway is in sight; (3) PF views through a head-up display (HUD) that displays primary flight guidance information and receives vertical and lateral guidance from PNF who views a head-down B-scope. PNF guidance is terminated upon PF's call-out that runway is in sight.
This study supplements prior and concurrent field trials testing the operational benefit of an Advanced Surface Movement Guidance and Control System (A-SMGCS). A-SMGCS comprises a range of new technologies for both the flight deck and the air traffic control tower enabling more efficient and safe airport surface movement. These technologies are expected to significantly increase the throughput at presently highly congested major airports without compromising safety. A flight deck A-SMGCS module is the onboard guidance system TARMAC-AS. This module consists of a controller pilot data link (DL) communication and an electronic moving map (EMM), which also displays airport surface traffic information to the pilot crew. TARMAC-AS is evaluated in an investigation involving twenty commercial pilots who performed a series of approach, landing and taxiing simulation trials that were completed in a fixed-base cockpit simulator. Evaluation was based on subjective questionnaires, effectiveness of taxi operation, and visual scanning strategies derived from eye-point-of-gaze measurements. Results support the notion that EMM + DL improve awareness of the global airport surface situation, particularly under conditions of low visibility, enabling more efficient and timely surface movements and avoidance of conflicting traffic. A potential negative impact of increased head-down times was not substantiated.