AIM Text
- Introduction. The most important aspects of vision and the techniques to scan for other aircraft are described in paragraph 8-1-6, Vision in Flight. Pilots should also be familiar with the following information to reduce the possibility of mid‐air collisions.
- Determining Relative Altitude. Use the horizon as a reference point. If the other aircraft is above the horizon, it is probably on a higher flight path. If the aircraft appears to be below the horizon, it is probably flying at a lower altitude.
- Taking Appropriate Action. Pilots should be familiar with rules on right‐of‐way, so if an aircraft is on an obvious collision course, one can take immediate evasive action, preferably in compliance with applicable Federal Aviation Regulations.
- Consider Multiple Threats. The decision to climb, descend, or turn is a matter of personal judgment, but one should anticipate that the other pilot may also be making a quick maneuver. Watch the other aircraft during the maneuver and begin your scanning again immediately since there may be other aircraft in the area.
- Collision Course Targets. Any aircraft that appears to have no relative motion and stays in one scan quadrant is likely to be on a collision course. Also, if a target shows no lateral or vertical motion, but increases in size, take evasive action.
- Recognize High Hazard Areas.
- Airways, especially near VORs, and Class B, Class C, Class D, and Class E surface areas are places where aircraft tend to cluster.
- Remember, most collisions occur during days when the weather is good. Being in a “radar environment” still requires vigilance to avoid collisions.
- Cockpit Management. Studying maps, checklists, and manuals before flight, with other proper preflight planning; e.g., noting necessary radio frequencies and organizing cockpit materials, can reduce the amount of time required to look at these items during flight, permitting more scan time.
- Windshield Conditions. Dirty or bug‐smeared windshields can greatly reduce the ability of pilots to see other aircraft. Keep a clean windshield.
- Visibility Conditions. Smoke, haze, dust, rain, and flying towards the sun can also greatly reduce the ability to detect targets.
- Visual Obstructions in the Cockpit.
- Pilots need to move their heads to see around blind spots caused by fixed aircraft structures, such as door posts, wings, etc. It will be necessary at times to maneuver the aircraft; e.g., lift a wing, to facilitate seeing.
- Pilots must ensure curtains and other cockpit objects; e.g., maps on glare shield, are removed and stowed during flight.
- Lights On.
- Day or night, use of exterior lights can greatly increase the conspicuity of any aircraft.
- Keep interior lights low at night.
- ATC Support. ATC facilities often provide radar traffic advisories on a workload‐permitting basis. Flight through Class C and Class D airspace requires communication with ATC. Use this support whenever possible or when required.
Source: FAA Aeronautical Information Manual · current edition · paragraph 8-1-8.
Research Notes
AIM 8-1-8 covers Effects of Vision and Optical Illusions on Flight — visual factors affecting flight safety.
Night vision:
- Takes ~30 minutes to fully adapt to darkness
- Rod cells (responsible for night vision) are NOT in the central macula — use off-center scanning at night
- Bright lights disrupt night vision for several minutes
- Use red lighting in the cockpit to preserve night vision
Optical illusions on approach:
- Wider-than-normal runway: appears closer/lower than actual — risk of high approach
- Narrower-than-normal runway: appears farther/higher than actual — risk of low approach
- Up-sloping runway: appears as steeper approach than actual
- Down-sloping runway: appears as shallower approach than actual
- Sloping terrain: similar illusions
- Featureless terrain ("black hole" approach over water/desert): tendency to go low
Defenses: Use VASI/PAPI when available. Cross-check airspeed and altitude. Don't rely on visual cues alone.
Reference: AIM 8-1-8; FAA-H-8083-25 Chapter 17.