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AIM

10/12/17

4

−4−10

ATC Clearances and Aircraft Separation

Information Region, in Class E airspace below
10,000 feet MSL. However, in airspace underlying a
Class B airspace area designated for an airport, or in
a VFR corridor designated through such as a Class B
airspace area, pilots are expected to comply with the
200 knot speed limit specified in 14 CFR
Section 91.117(c).

k.

For operations in a Class C and Class D surface

area, ATC is authorized to request or approve a speed
greater than the maximum indicated airspeeds
prescribed for operation within that airspace (14 CFR
Section 91.117(b)).

NOTE

Pilots are expected to comply with the maximum speed of
200 knots when operating beneath Class B airspace or in
a Class B VFR corridor (14 CFR Section 91.117(c)
and (d)).

l.

When in communications with the ARTCC or

approach control facility, pilots should, as a good
operating practice, state any ATC assigned speed
restriction on initial radio contact associated with an
ATC communications frequency change.

4

−4−13. Runway Separation

Tower controllers establish the sequence of arriving
and departing aircraft by requiring them to adjust
flight or ground operation as necessary to achieve
proper spacing. They may “HOLD” an aircraft short
of the runway to achieve spacing between it and an
arriving aircraft; the controller may instruct a pilot to
“EXTEND DOWNWIND” in order to establish
spacing from an arriving or departing aircraft. At
times a clearance may include the word “IMMEDI-
ATE.” For example: “CLEARED FOR
IMMEDIATE TAKEOFF.” In such cases “IMMEDI-
ATE” is used for purposes of air traffic separation. It
is up to the pilot to refuse the clearance if, in the pilot’s
opinion, compliance would adversely affect the
operation.

REFERENCE

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.

NOTE

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.

NOTE

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.