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AIM

10/12/17

4−3−1

Airport Operations

Section 3. Airport Operations

4−3−1. General

Increased traffic congestion, aircraft in climb and

descent attitudes, and pilot preoccupation with

cockpit duties are some factors that increase the

hazardous accident potential near the airport. The

situation is further compounded when the weather is

marginal, that is, just meeting VFR requirements.

Pilots must be particularly alert when operating in the

vicinity of an airport. This section defines some rules,

practices, and procedures that pilots should be

familiar with and adhere to for safe airport operations.

4−3−2. Airports with an Operating Control

Tower

a. When operating at an airport where traffic

control is being exercised by a control tower, pilots

are required to maintain two−way radio contact with

the tower while operating within the Class B, Class C,

and Class D surface area unless the tower authorizes

otherwise. Initial callup should be made about

15 miles from the airport. Unless there is a good

reason to leave the tower frequency before exiting the

Class B, Class C, and Class D surface areas, it is a

good operating practice to remain on the tower

frequency for the purpose of receiving traffic

information. In the interest of reducing tower

frequency congestion, pilots are reminded that it is

not necessary to request permission to leave the tower

frequency once outside of Class B, Class C, and

Class D surface areas. Not all airports with an

operating control tower will have Class D airspace.

These airports do not have weather reporting which

is a requirement for surface based controlled

airspace, previously known as a control zone. The

controlled airspace over these airports will normally

begin at 700 feet or 1,200 feet above ground level and

can be determined from the visual aeronautical

charts. Pilots are expected to use good operating

practices and communicate with the control tower as

described in this section.

b. When necessary, the tower controller will issue

clearances or other information for aircraft to

generally follow the desired flight path (traffic

patterns) when flying in Class B, Class C, and Class D

surface areas and the proper taxi routes when

operating on the ground. If not otherwise authorized

or directed by the tower, pilots of fixed−wing aircraft

approaching to land must circle the airport to the left.

Pilots approaching to land in a helicopter must avoid

the flow of fixed−wing traffic. However, in all

instances, an appropriate clearance must be received

from the tower before landing.

FIG 4−3−1

Components of a Traffic Pattern

NOTE−

This diagram is intended only to illustrate terminology

used in identifying various components of a traffic pattern.

It should not be used as a reference or guide on how to enter

a traffic pattern.

c. The following terminology for the various

components of a traffic pattern has been adopted as

standard for use by control towers and pilots (See

FIG 4−3−1):

1. Upwind leg. A flight path parallel to the

landing runway in the direction of landing.

2. Crosswind leg. A flight path at right angles

to the landing runway off its takeoff end.

3. Downwind leg. A flight path parallel to the

landing runway in the opposite direction of landing.

4. Base leg. A flight path at right angles to the

landing runway off its approach end and extending

from the downwind leg to the intersection of the

extended runway centerline.

5. Final approach. A flight path in the

direction of landing along the extended runway

centerline from the base leg to the runway.

6. Departure. The flight path which begins

after takeoff and continues straight ahead along the

extended runway centerline. The departure climb

continues until reaching a point at least 

1

/

2

 mile

3/29/18

AIM