Aeronautical Information Manual (AIM), page 240

Index   239 -- Page 240 -- 241

opinion, compliance would adversely affect the
AIM, Paragraph 4-3-15 , Gate Holding due to Departure Delays

4-4-14. Visual Separation
a. 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:

1. The tower controller sees the aircraft
involved and issues instructions, as necessary, to
ensure that the aircraft avoid each other.

2. 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.
Traffic is no longer a factor when during approach phase
the other aircraft is in the landing phase of flight or
executes a missed approach; and during departure or
en route, when the other aircraft turns away or is on a
diverging course.
b. 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 responsi-
bility for wake turbulence separation. Visual
separation is prohibited behind super aircraft.
When a pilot has been told to follow another aircraft or to
provide visual separation from it, the pilot should promptly
notify the controller if visual contact with the other aircraft
is lost or cannot be maintained or if the pilot cannot accept
the responsibility for the separation for any reason.

c. 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.
d. 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.

4-4-15. Use of Visual Clearing Procedures

a. Before Takeoff. Prior to taxiing onto a runway
or landing area in preparation for takeoff, pilots
should scan the approach areas for possible landing
traffic and execute the appropriate clearing maneu-
vers to provide them a clear view of the approach
b. Climbs and Descents. During climbs and
descents in flight conditions which permit visual
detection of other traffic, pilots should execute gentle
banks, left and right at a frequency which permits
continuous visual scanning of the airspace about

c. Straight and Level. Sustained periods of
straight and level flight in conditions which permit
visual detection of other traffic should be broken at
intervals with appropriate clearing procedures to
provide effective visual scanning.

d. Traffic Pattern. Entries into traffic patterns
while descending create specific collision hazards
and should be avoided.

e. Traffic at VOR Sites. All operators should
emphasize the need for sustained vigilance in the
vicinity of VORs and airway intersections due to the
convergence of traffic.

4-4-10 ATC Clearances and Aircraft Separation

Page 240 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   239 -- Page 240 -- 241