Visual Scanning Techniques

The Importance of Vision in Flight

The human eye is one of the most complex and vital sensory organs, responsible for transmitting visual information to the brain for recognition and storage. It is estimated that 80 percent of our total information intake is through our eyes. In aviation, vision is essential for monitoring attitude, speed, direction, and proximity to other aircraft and obstacles. As air traffic density increases, so does the risk of midair collisions, making an understanding of visual limitations crucial for pilot safety.

Profile of Midair Collisions

Studies indicate that most midair collisions occur in daylight and under Visual Flight Rules (VFR) conditions. The majority happen within five miles of an airport, particularly in areas of high traffic density, and often on weekends when more pilots are flying.

Key Findings:

• Most midair collisions occur at or below 3,000 feet, often in the traffic pattern, especially on final approach.

• The majority involve one aircraft overtaking another rather than head-on collisions.

• Experience level does not determine risk; both novice and experienced pilots have been involved in collisions.

Causes of Midair Collisions

While increasing air traffic and closing speeds contribute to risk, the primary cause is pilot failure to see and avoid other aircraft. Given that a pilot needs at least 10 seconds to detect, identify, and react to conflicting traffic, high closing speeds can make avoidance impossible if the aircraft is detected too late.

Limitations of the Human Eye

The human eye has several limitations that can hinder a pilot’s ability to detect other aircraft:

1. Narrow Field of Sharp Vision - The fovea, the part of the retina responsible for sharp central vision, covers only a small portion of the visual field. Objects outside this narrow area appear blurry unless actively scanned.

2. Blind Spots - Each eye has a physiological blind spot where the optic nerve connects to the retina. If an aircraft falls into this area, it may go unnoticed unless the pilot shifts their gaze.

3. Empty-Field Myopia - In conditions where there are no distinct objects in the visual field (such as a clear blue sky), the eyes tend to focus at a fixed distance (10 to 30 feet) rather than at infinity, making it harder to spot distant aircraft.

4. Motion-Induced Blindness - A stationary object in the peripheral vision can disappear from perception if the observer’s focus remains fixed elsewhere, which is particularly dangerous when scanning for moving aircraft.

5. Contrast and Lighting Effects - Aircraft visibility is affected by background contrast. A dark aircraft against a bright sky or a light-colored aircraft against clouds may blend in, making it difficult to detect.

6. Glare and Reflections - Sun glare and windshield reflections can obscure vision, making it harder to spot aircraft at certain angles.

7. Reaction Time - Even after an aircraft is detected, the time required for recognition, decision-making, and maneuvering can delay evasive action, increasing the risk of collision.

More information about the limitations of the human eye are available in the section "Human Eye"

Effective Scanning Techniques

There is no perfect scan technique, but pilots should develop a consistent, effective method.

Scanning Methods:

• Side-to-Side Block Scan: Move systematically from left to right in 10-15 degree increments, pausing at each interval to focus.

• Front-to-Side Block Scan: Start at the center, scan to one side, return to center, then scan to the other side.

Figure 1 Scanning Techniques (FAASafety.gov)

The Time-Sharing Plan

Pilots should balance external scanning with necessary panel monitoring. A recommended ratio is:

• 3-4 seconds for instrument scan

• 16-17 seconds for outside scanning

Instrument Scan Priorities:

1. Attitude indicator

2. Directional gyro

3. Altimeter

4. Airspeed indicator

5. Vertical speed indicator (VSI)

6. Turn coordinator

Collision Avoidance Checklist

1. Check Yourself: Ensure you are well-rested and alert.

2. Plan Ahead: Minimize distractions by organizing charts and cockpit materials before takeoff.

3. Clean Windows: A dirty windshield can obscure critical visual cues.

4. Follow Standard Procedures: Adhere to correct altitudes and pattern practices.

5. Use Proper Communication: Monitor and broadcast position on common traffic advisory frequencies (CTAF).

6. Use Landing and Anti-Collision Lights: Enhance aircraft visibility.

7. Know High-Risk Areas: Be extra vigilant near airports and congested airspace.

8. Utilize Technology: Use Traffic Collision Avoidance Systems (TCAS) and ADS-B where available.

9. Maintain an Effective Scan: Regularly scan for traffic to maximize detection.

Midair collisions are largely preventable through awareness and proper visual scanning techniques. Understanding the limitations of human vision, maintaining an effective scan, and adhering to best practices can significantly reduce collision risk. Pilots should develop disciplined scanning habits and remain vigilant at all times to ensure safety in the air.

For more information you can read this great article about visual scanning techniques published by the FAA Safety Team: https://www.faasafety.gov/gslac/ALC/libview_normal.aspx?id=6851