4/20/23 

AIM 

1.  The segmented circle. 

Located in a position affording maximum visibility to pilots in the air and on the 

ground and providing a centralized location for other elements of the system. 

2.  The wind direction indicator. 

A wind cone, wind sock, or wind tee installed near the operational 

runway to indicate wind direction. The large end of the wind cone/wind sock points into the wind as does the 

large end (cross bar) of the wind tee. In lieu of a tetrahedron and where a wind sock or wind cone is collocated 

with a wind tee, the wind tee may be manually aligned with the runway in use to indicate landing direction. These 

signaling devices may be located in the center of the segmented circle and may be lighted for night use. Pilots 

are cautioned against using a tetrahedron to indicate wind direction. 

3.  The landing direction indicator. 

A tetrahedron is installed when conditions at the airport warrant its 

use. It may be used to indicate the direction of landings and takeoffs. A tetrahedron may be located at the center 

of a segmented circle and may be lighted for night operations. The small end of the tetrahedron points in the 

direction of landing. Pilots are cautioned against using a tetrahedron for any purpose other than as an indicator 

of landing direction. Further, pilots should use extreme caution when making runway selection by use of a 

tetrahedron in very light or calm wind conditions as the tetrahedron may not be aligned with the designated 

calm

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wind runway. At airports with control towers, the tetrahedron should only be referenced when the control 

tower is not in operation. Tower instructions supersede tetrahedron indications. 

4.  Landing strip indicators. 

Installed in pairs as shown in the segmented circle diagram and used to show 

the alignment of landing strips. 

5.  Traffic pattern indicators. 

Arranged in pairs in conjunction with landing strip indicators and used to 

indicate the direction of turns when there is a variation from the normal left traffic pattern. (If there is no 

segmented circle installed at the airport, traffic pattern indicators may be installed on or near the end of the 

runway.) 

c. 

Preparatory to landing at an airport without a control tower, or when the control tower is not in operation, 

pilots should concern themselves with the indicator for the approach end of the runway to be used. When 

approaching for landing, all turns must be made to the left unless a traffic pattern indicator indicates that turns 

should be made to the right. If the pilot will mentally enlarge the indicator for the runway to be used, the base 

and final approach legs of the traffic pattern to be flown immediately become apparent. Similar treatment of the 

indicator at the departure end of the runway will clearly indicate the direction of turn after takeoff. 

d. 

When two or more aircraft are approaching an airport for the purpose of landing, the pilot of the aircraft 

at the lower altitude has the right

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way over the pilot of the aircraft at the higher altitude. However, the pilot 

operating at the lower altitude should not take advantage of another aircraft, which is on final approach to land, 

by cutting in front of, or overtaking that aircraft. 

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5.  Unexpected Maneuvers in the Airport Traffic Pattern 

There have been several incidents in the vicinity of controlled airports that were caused primarily by aircraft 

executing unexpected maneuvers. ATC service is based upon observed or known traffic and airport conditions. 

Controllers establish the sequence of arriving and departing aircraft by requiring them to adjust flight as 

necessary to achieve proper spacing. These adjustments can only be based on observed traffic, accurate pilot 

reports, and anticipated aircraft maneuvers. Pilots are expected to cooperate so as to preclude disrupting traffic 

flows or creating conflicting patterns. The pilot

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in

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command of an aircraft is directly responsible for and is the 

final authority as to the operation of the aircraft. On occasion it may be necessary for pilots to maneuver their 

aircraft to maintain spacing with the traffic they have been sequenced to follow. The controller can anticipate 

minor maneuvering such as shallow “S” turns. The controller cannot, however, anticipate a major maneuver such 

as a 360 degree turn. If a pilot makes a 360 degree turn after obtaining a landing sequence, the result is usually 

a gap in the landing interval and, more importantly, it causes a chain reaction which may result in a conflict with 

following traffic and an interruption of the sequence established by the tower or approach controller. Should a 

pilot decide to make maneuvering turns to maintain spacing behind a preceding aircraft, the pilot should always 

advise the controller if at all possible. Except when requested by the controller or in emergency situations, a 360 

Airport Operations 

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