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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