AIM Text
- Visual separation is a means employed by ATC to separate aircraft in terminal areas and en route airspace in the NAS. There are two methods employed to effect this separation:
- The tower controller sees the aircraft involved and issues instructions, as necessary, to ensure that the aircraft avoid each other.
- A pilot sees the other aircraft involved and upon instructions from the controller provides separation by maneuvering the aircraft to avoid it. When pilots accept responsibility to maintain visual separation, they must maintain constant visual surveillance and not pass the other aircraft until it is no longer a factor.
- A pilot's acceptance of instructions to follow another aircraft or provide visual separation from it is an acknowledgment that the pilot will maneuver the aircraft as necessary to avoid the other aircraft or to maintain in-trail separation. In operations conducted behind heavy aircraft, or a small aircraft behind a B757 or other large aircraft, it is also an acknowledgment that the pilot accepts the responsibility for wake turbulence separation. Visual separation is prohibited behind super aircraft.
- Scanning the sky for other aircraft is a key factor in collision avoidance. Pilots and copilots (or the right seat passenger) should continuously scan to cover all areas of the sky visible from the cockpit. Pilots must develop an effective scanning technique which maximizes one's visual capabilities. Spotting a potential collision threat increases directly as more time is spent looking outside the aircraft. One must use timesharing techniques to effectively scan the surrounding airspace while monitoring instruments as well.
- Since the eye can focus only on a narrow viewing area, effective scanning is accomplished with a series of short, regularly spaced eye movements that bring successive areas of the sky into the central visual field. Each movement should not exceed ten degrees, and each area should be observed for at least one second to enable collision detection. Although many pilots seem to prefer the method of horizontal back-and-forth scanning every pilot should develop a scanning pattern that is not only comfortable but assures optimum effectiveness. Pilots should remember, however, that they have a regulatory responsibility (14 CFR section 91.113(a)) to see and avoid other aircraft when weather conditions permit.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-4-14.
Research Notes
AIM 4-4-14 covers visual separation — the procedure for pilots to accept responsibility for separation from another aircraft based on visual contact.
The visual separation framework: When two aircraft are operating in controlled airspace and the controller offers visual separation, the trailing aircraft's pilot can accept by reporting "traffic in sight" and offering to maintain visual separation. This shifts separation responsibility to the pilot, freeing the controller to use other separation techniques.
Pilot's responsibility once accepted:
- Maintain visual contact with the traffic
- Maintain safe separation (no specific minimum — see-and-avoid standard)
- Report if you lose sight ("lost traffic in sight")
When ATC may offer visual separation: Typically when approach control is sequencing traffic for the same runway, or when a faster aircraft is overtaking a slower aircraft. The controller's typical phraseology: "Cessna Two-Three-Uniform, traffic at one o'clock, three miles, opposite direction, Boeing 737, descending through five thousand. Are you visual?"
Common errors:
- Saying "traffic in sight" when actually looking at the wrong aircraft
- Losing sight after accepting visual separation and not reporting
- Failing to maintain safe separation while "maintaining visual"
Reference: AIM 4-4-14; AIM 4-4-13.