See and Avoid
The “see and avoid” method of collision avoidance is used as the primary means of separation between aircraft operating under visual flight rules. Just as it sounds, this method involves looking for air traffic and maneuvering as necessary.
While your eyes are able to see a wide area at once, only a small area in the center of the visual field is sharply focused. As a result, pilot’s use a visual scanning technique in order to examine each area of sky for other aircraft.
An airplane is visible ten times further away if you are looking directly at it. Visual scanning technique involves systematically looking at every portion of the sky.
To accomplish this, use short and regularly spaced eye movements. Examine about ten degrees of sky at a time, and stay focused on each ten degree portion of the sky for at least one second. This allows your mind enough time to examine what your eyes are focused on.
Since other aircraft might be climbing or descending, scan above and below the horizon, as well as at your own altitude.
As a general rule, you keep your eyes focused no more than 4 to 5 seconds on anything inside the airplane for every 16 seconds spent scanning outside the airplane. In other words, you eyes should be focused inside the airplane no more than 1/4 to 1/3 of the time.
Whenever you are practicing maneuvers, visually scan the entire area for traffic prior to beginning a maneuver.
Relative Altitude
When you see another aircraft, notice its altitude relative to yours. If an aircraft appears to be above the horizon, it is probably on a higher flight path. An aircraft below the horizon is probably at a lower altitude. However, just because an aircraft is currently at a different altitude does not necessarily mean it will stay there. Remember to watch for aircraft which could be climbing or descending.
Relative Motion
Also watch the aircraft’s relative motion. If an aircraft appears to have no motion relative to your airplane, it is likely flying directly toward you. Because of this lack of relative motion and the aerodynamic design of aircraft, an aircraft approaching head on is more difficult to see.
High Hazard Areas
Be aware of areas that are more congested. Most mid air collisions occur during times of good weather, usually near a high traffic area. Examples of high hazard areas include navigational aids, airports, along federal airways, and in areas used for pilot training.
It is recommended to execute gentle banks when climbing or descending in a high hazard area. This allows you to better see areas that may be blocked by portions of your own airplane. The FAA recommends gentle banks when climbing or descending along a federal airway. These airways are primarily used by aircraft under instrument flight rules, where air traffic control radar coverage is not available. Pilot's of VFR aircraft can use them, as well, at their own discretion. If you choose to do so, these gentle banks are recommended because you may be climbing or descending through several airplanes along your same route of flight.
Obstructions to Visibility
Keep a clean windshield. It’s hard to spot other aircraft during the flight if you are looking through a windshield that is dirty or covered in smashed bugs. Other obstructions to visibility include portions of the airplane itself. It is fine to occasionally perform gentle banks left and right in order to allow you to scan areas blocked by portions of the airplane.
Organization
Organize materials needed during the flight beforehand, and make note of radio frequencies to be used. This will reduce the amount of time spent looking inside the airplane during the flight.
Scanning for Traffic at Night
Your eyes are contain two different types of light receptors, called cones and rods. The cones do a good job of providing sharp detail and good color depth. However, cones require bright light for their operation. Rods are adapted to work in low light conditions, but provide little detail or color depth.
Cones are concentrated in the center of your visual field, providing the sharp, high color area of vision you use in bright light conditions. The rods are distributed elsewhere in the eye, providing you a peripheral and night vision. As a result of this distribution of cones and rods, the area you see most clearly with during the day becomes more or less blind at night. In low light conditions, we become more reliant on our peripheral vision.
When scanning for traffic at night, you have a harder time seeing objects you are looking at directly. To most effectively scan for traffic at night, use your peripheral vision. This method of scanning is called off center viewing.