Advisory Circular 90-66a
U.S. DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
Advisory Circular 90-66A
Subject: RECOMMENDED STANDARD TRAFFIC PATTERNS AND PRACTICES FOR
AERONAUTICAL OPERATIONS AT AIRPORTS WITHOUT OPERATING CONTROL
This advisory circular (AC) calls attention to regulatory
requirements and recommended procedures for aeronautical
operations at airports without operating control towers. It
recommends traffic patterns and operational procedures for
aircraft, lighter than air, glider, parachute, rotorcraft, and
ultralight vehicle operations where such use is not in conflict
with existing procedures in effect at those airports.
AC 90-66, Recommended Standard Traffic Patterns for Airplane
Operations at Uncontrolled Airports, dated February 27, 1975, is
3. PRINCIPAL CHANGES.
This AC has been updated to reflect current
procedures at airports without operating control towers.
Principal changes include: adding on "Other Traffic Pattern"
section, amending appendix charts to remain consistent with the
Airman's Information Manual (AIM), expanding the "Related Reading
Material" section from "airplane" to "aeronautical" operations,
adding definition and references to Common Traffic Advisory
Frequency (CTAF), acknowledging straight-in approaches are not
prohibited but may be operationally advantageous, and adding a
paragraph on wake turbulence.
a. Airports Without Operating Control Towers. Airports without
control towers or an airport with a control tower which is not
operating. These airports are commonly referred to as
non-towered, uncontrolled, or part-time towered airports.
b. Common Traffic Advisory Frequency (CTAF). A frequency designed
for the purpose of carrying out airport advisory practices while
operating to or from an airport without an operating control
tower. The CTAF may be a UNICOM, MULTICOM, flight service
station, or tower frequency and is identified in appropriate
5. RELATED READING MATERIAL.
a. Airport Facility Directory (AFD).
b. Airman's Information Manual (AIM).
c. Fly Neighborly Guide, Helicopter Association International.
d. Aviation USA, Aircraft Owners and Pilots
e. State aviation publications.
f. Various pilot guides.
g. Pilot Operations at Nontowered Airports, AOPA Air Safety
h. Guidelines for the Operation of Ultralight Vehicles at
Existing Airports, United States Ultralight Association.
i. Facts for Pilots, United States Parachute Association.
j. The latest addition of the following AC's also contain
information applicable to operations at airports without
operating control towers:
(1) AC 90-23, Aircraft Wake Turbulence.
(2) AC 90-42, Traffic Advisory Practices at Airports Without
Operating Control Towers.
(3) AC 90 48, Pilot's Role in Collision Avoidance.
(4) AC 91-32, Safety In and Around Helicopters.
(5) AC 103-6, Ultralight Vehicle Operations-Airports, Air Traffic
Control, and Weather.
(6) AC 105-2, Sport Parachute Jumping.
6. BACKGROUND AND SCOPE.
a. Regulatory provisions relating to traffic patterns are found
in Parts 91, 93, and 97 of the Federal Aviation Regulations
(FAR). The airport traffic patterns contained in Part 93 relate
primarily to those airports where there is a need for unique
traffic pattern procedures not provided for in Part 91. Part 97
addresses instrument approach procedures. At airports without
operating control towers, Part 91 requires only that pilots of
airplanes approaching to land make all turns to the left unless
light signals or visual markings indicate that turns should be
made to the right.
b. The Federal Aviation Administration (FAA) believes that
observance of a standard traffic pattern and the use of CTAF
procedures as detailed in AC 90~2 will improve the safety and
efficiency of aeronautical operations at airports without
operating control towers.
7. GENERAL OPERATING PRACTICES.
a. Use of standard traffic patterns for all aircraft and CTAF
procedures by radio-equipped aircraft are recommended at all
airports without operating control towers. However, it is
recognized that other traffic patterns may already be in common
use at some airports or- that special circumstances or conditions
exist that may prevent use of the standard traffic pattern.
b. The use of any traffic pattern procedure does not alter the
responsibility of each pilot to see and avoid other aircraft.
Pilots are encouraged to participate in "Operation Lights On,"
which is a voluntary pilot safety program described in the AIM
designed to enhance the "see-and-avoid" requirement.
c. As part of the preflight familiarization with all available
information concerning a flight, each pilot should review all
appropriate publications (AFD, AIM, Notices to Airmen (NOTAM),
etc.), for pertinent information on current traffic patterns at
the departure and arrival airports.
d. It is recommended that pilots utilize visual indicators, such
as the segmented circle, wind direction indicator, landing
direction indicator, and traffic pattern indicators which provide
traffic pattern information.
e. The FAA encourages pilots to use the standard traffic pattern.
However, for those pilots who choose to execute a straight-in
approach, maneuvering for and execution of the approach should be
completed so as not to disrupt the flow of arriving and departing
traffic. Therefore, pilots operating in the traffic pattern
should be alert at al] times to aircraft executing straight-in
f. Pilots who wish to conduct instrument approaches should be
particularly alert for other aircraft in the pattern so as to
avoid interrupting the flow of traffic. Position reports on the
CTAF should include distance and direction from the airport, as
well as the pilot's intentions upon completion of the approach.
g. Pilots of inbound nonradio-equipped aircraft should determine
the runway in use prior to entering the traffic pattern by
observing the landing direction indicator or by other means.
Pilots should be aware that procedures at airports without
operating control towers generally do not require the use of
two-way radios; therefore, pilots should be especially vigilant
for other aircraft while operating in the traffic pattern.
h. Wake turbulence is generated by all aircraft. Therefore,
pilots should expect to encounter turbulence while operating in a
traffic pattern and in proximity to other aircraft. Aircraft
components and equipment can be damaged by wake turbulence. In
flight, avoid the area below and behind the aircraft generating
turbulence especially at low altitude where even ~ momentary wake
encounter can be hazardous. All operators should be aware of the
potential adverse effects that their wake, rotor or propeller
turbulence has on light aircraft and ultralight vehicles.
8. RECOMMENDED STANDARD TRAFFIC PATTERN
Airport owners and operators, in coordination with the FAA, are
responsible for establishing traffic patterns. However, the FAA
encourages airport owners and operators to establish traffic
patterns as recommended in this AC. Further, left traffic
patterns should be established except where obstacles, terrain,
and noise-sensitive areas dictate otherwise. Appendix 1 contains
diagrams for recommended standard traffic patterns.
a. Prior to entering the traffic pattern at an airport without an
operating control tower, aircraft should avoid the flow of
traffic until established on the entry leg. For example, wind and
landing direction indicators can be checked while at an altitude
above the traffic pattern. When the proper traffic pattern
direction has been determined, the pilot should then proceed to a
point well clear of the pattern before descending to the pattern
b. Arriving aircraft should be at the appropriate traffic pattern
altitude before entering the traffic pattern. Entry to the
downwind leg should be at a 45 degree angle abeam the midpoint of
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