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AIM

10/12/17

2

−2−1

Air Navigation and Obstruction Lighting

Section 2. Air Navigation and Obstruction Lighting

2

−2−1. Aeronautical Light Beacons

a.

An aeronautical light beacon is a visual

NAVAID displaying flashes of white and/or colored
light to indicate the location of an airport, a heliport,
a landmark, a certain point of a Federal airway in
mountainous terrain, or an obstruction. The light used
may be a rotating beacon or one or more flashing
lights. The flashing lights may be supplemented by
steady burning lights of lesser intensity.

b.

The color or color combination displayed by a

particular beacon and/or its auxiliary lights tell
whether the beacon is indicating a landing place,
landmark, point of the Federal airways, or an
obstruction. Coded flashes of the auxiliary lights, if
employed, further identify the beacon site.

2

−2−2. Code Beacons and Course Lights

a. Code Beacons.

The code beacon, which can be

seen from all directions, is used to identify airports
and landmarks. The code beacon flashes the three or
four character airport identifier in International
Morse Code six to eight times per minute. Green
flashes are displayed for land airports while yellow
flashes indicate water airports.

b. Course Lights.

The course light, which can be

seen clearly from only one direction, is used only with
rotating beacons of the Federal Airway System:
two course lights, back to back, direct coded flashing
beams of light in either direction along the course of
airway.

NOTE

Airway beacons are remnants of the “lighted” airways
which antedated the present electronically equipped
federal airways system. Only a few of these beacons exist
today to mark airway segments in remote mountain areas.
Flashes in Morse code identify the beacon site.

2

−2−3. Obstruction Lights

a.

Obstructions are marked/lighted to warn airmen

of their presence during daytime and nighttime
conditions. They may be marked/lighted in any of the
following combinations:

1. Aviation Red Obstruction Lights.

Flash-

ing aviation red beacons (20 to 40 flashes per minute)
and steady burning aviation red lights during
nighttime operation. Aviation orange and white paint
is used for daytime marking.

2. Medium Intensity Flashing White

Obstruction Lights.

Medium intensity flashing

white obstruction lights may be used during daytime
and twilight with automatically selected reduced
intensity for nighttime operation. When this system
is used on structures 500 feet (153m) AGL or less in
height, other methods of marking and lighting the
structure may be omitted. Aviation orange and white
paint is always required for daytime marking on
structures exceeding 500 feet (153m) AGL. This
system is not normally installed on structures less
than 200 feet (61m) AGL.

3. High Intensity White Obstruction Lights.

Flashing high intensity white lights during daytime
with reduced intensity for twilight and nighttime
operation. When this type system is used, the marking
of structures with red obstruction lights and aviation
orange and white paint may be omitted.

4. Dual Lighting.

A combination of flashing

aviation red beacons and steady burning aviation red
lights for nighttime operation and flashing high
intensity white lights for daytime operation. Aviation
orange and white paint may be omitted.

5. Catenary Lighting.

Lighted markers are

available for increased night conspicuity of high

voltage (69KV or higher) transmission line catenary
wires. Lighted markers provide conspicuity both day
and night.

b.

Medium intensity omnidirectional flashing

white lighting system provides conspicuity both day
and night on catenary support structures. The unique
sequential/simultaneous flashing light system alerts
pilots of the associated catenary wires.

c.

High intensity flashing white lights are being

used to identify some supporting structures of
overhead transmission lines located across rivers,
chasms, gorges, etc. These lights flash in a middle,
top, lower light sequence at approximately 60 flashes
per minute. The top light is normally installed near
the top of the supporting structure, while the lower
light indicates the approximate lower portion of the