Goto Section: 87.481 | 87.525 | Table of Contents
Revised as of September 1, 2021
Goto Year:2020 |
§ 87.483 Audio visual warning systems.
An audio visual warning system (AVWS) is a radar-based obstacle
avoidance system. AVWS activates obstruction lighting and transmits VHF
audible warnings to alert pilots of potential collisions with
land-based obstructions. The AVWS operations are limited to locations
where natural and man-made obstructions exist. The continuously
operating radar calculates the location, direction and groundspeed of
nearby aircraft that enter one of two warning zones reasonably
established by the licensee. As aircraft enter the first warning zone,
the AVWS activates obstruction lighting. If the aircraft continues
toward the obstacle and enters the second warning zone, the VHF radio
transmits an audible warning describing the obstacle.
(a) Radiodetermination (radar) frequencies. Frequencies authorized
under § 87.475(b)(8) of this chapter are available for use by an AVWS.
The frequency coordination requirements in § 87.475(a) of this chapter
(b) VHF audible warning frequencies. Frequencies authorized under
§ 87.187(j), § 87.217(a), § 87.241(b), and § 87.323(b) (excluding 121.950
MHz) of this chapter are available for use by an AVWS. Multiple
frequencies may be authorized for an individual station, depending on
need and the use of frequencies assigned in the vicinity of a proposed
AVWS facility. Use of these frequencies is subject to the following
(1) The output power shall not exceed −3 dBm watts for each frequency
(2) The antenna used in transmitting the audible warnings must be
omnidirectional with a maximum gain equal to or lower than a half-wave
centerfed dipole above 30 degrees elevation, and a maximum gain of + 5
dBi from horizontal up to 30 degrees elevation.
(3) The audible warning shall not exceed two seconds in duration. No
more than six audible warnings may be transmitted in a single transmit
cycle, which shall not exceed 12 seconds in duration. An interval of at
least twenty seconds must occur between transmit cycles.
[ 78 FR 61207 , Oct. 3, 2013]
Subpart R [Reserved]
Subpart S—Automatic Weather Stations (AWOS/ASOS)
Goto Section: 87.481 | 87.525
Goto Year: 2020 |
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