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Scanning is a continuous process used by the pilot to maintain situational awareness. Pilots must develop an effective scanning technique to maximizes their visual capabilities. Approximately 90% of time looking outside, 10% spent scanning instruments. When moving eyes from inside to outside, or vice versa, give your eyes time to adjust focus.
Effective scanning also helps avoid "empty field myopia". This condition usually occurs when flying above the clouds or in a haze layer that provides nothing specific to focus on outside the aircraft. This causes the eyes to relax and seek a comfortable focal distance. For the pilot, this means looking without seeing, which is dangerous.
When we are soaring we need to adapt the scan to our conditions. We still need a scan for traffic, but we also need more information about the soaring conditions. The clouds, the wind, both where we are and ahead on track.
Look out is the term used to describe an external visual scan for traffic. It is the pilot's responsibility to see and avoid traffic. While the eyes can observe an approximate 200° arc of the horizon at one glance, a very small central area (approximately 10°), called the fovea detects the most detail. The larger peripheral area of the eye is more sensitive to contrast and movement.
Thus, one must use techniques to efficiently scan for traffic. Each scan movement should cover approximately 10°, and each area should be observed for at least a second to enable detection.
External scan should be broken down into about 10° increments, spending about a second on each segment. Focus the eye at 10° increments at a time, about a second or two when looking for traffic.
Vertically, the area of interest for traffic avoidance is plus or minus about 10° from your level.
Two scanning patterns described below have proved to be very effective for pilots and involve the 'block' system of scanning. This system is based on the premise that traffic detection can be made only through a series of eye fixations at different points in space. In application, the viewing area is divided into segments, and the pilot methodically scans for traffic in each block in sequential order.
Start at the far left of your visual area and make a methodical sweep to the right, pausing very briefly in each block of the viewing area to focus your eyes. At the end of the scan, return to and scan the instrument panel and then repeat the external scan.
Start in the centre block of your visual field (looking ahead over the nose); move to the left, focusing very briefly in each block, then swing quickly back to the centre block after reaching the last block on the left and repeat the action to the right. Then, after scanning the instrument panel, repeat the external scan.
Those generic aviation scans are good for general aviation but for soaring we have specialized requirements. We need to observe the wind on the ground, the wind at our altitude, keep awareness of landout options, and keep that yawstring in view.
Because we often fly in high traffic environments we might want to alter our scan to focus more on the more likely threats.
When we are on an energy line (ridge, wave, or convergence) the most likely threat is coming along the energy line. So we should alter our scan to look along the energy line more often.
While travelling along an energy line, especially ridge or wave where the wind is likely to be perpendicular to the energy line, if you keep the glider stable and keep the nose pointed at a reference point in the distance, you can observe your drift relative to the terrain (or to cloud that is stationary relative to the ground). This will indicate the sideways wind component. Headwind/tailwind can be found by comparing GPS groundspeed with airspeed (useful to include this in your instrument scan).
When we are thermalling we can adapt our lookout to be more look ahead, pause, look ahead, pause, look ahead, etc to cover the whole 360° of the sky. With an occasional scan of the instruments, of cause. This keeps the yaw string in view most of the time, which is handy.
When looking ahead in the turn I generally look 20° or 30° ahead of the nose in the turn, because that's where I'm going.
To assess the wind drift while circling, check down to establish your location over the ground, then repeat this as part of your scan maybe once a turn or so. The amount and direction of your drift gives you your wind speed and direction at your altitude.
There is a tendency to go where you look. When driving along a two lane road if you look ahead along your lane you will tend to track straight along your lane. If you look at the oncoming traffic you tend to wander toward them. If you look at roadside obstacles you tend to wander toward them.
When flying, you should look where you want to go. For example, when flying the downwind leg of a circuit, look along the extended line of the downwind at your altitude. Keep your scan going, of course. If you look at the runway you will tend to veer towards the runway and crowd your circuit. Also looking down tends to lead to dropping the nose and speeding up.
A similar thing happens when soaring close to terrain. If you look at the mountain beside you, you tend to veer towards it. Look along your intended path and you'll tend to follow that. So when flying along a ridge below or close to the top, look along your intended path upwind of the ridgeline, not at the scary rocks beside you. This also helps you judge the amount of offset for drift you need.
When circling close to terrain, look ahead at your level. If you look down you tend to drop the nose and fall out of your circle. The ground is big and moves slowly. You can tell where it is from your peripheral vision and your usual scan. No need to stare at it.
Briefing prepared by Phil Plane.
This work is licensed under a Creative Commons Attribution 4.0 International License