[TowerTalk] Obstruction Lighting

[Larrie Sutliff]

Regulations concerning antenna structure reporting to the FAA may be found
in the FCC Rules, 47CFR Part 17, "Construction, Marking and Lighting of
Antenna Structures."  Antenna structure heights requiring notification of
the FAA are covered in Section 17.7; generally notification is required for
towers exceeding 200 feet above ground level.  However, in the vicinity of
an airport, towers extending above imaginary surfaces which slope outward
and upward from the nearest point on the nearest runway, as described in
Section 17.7(b), require FAA notification (100:1 slope out to 20,000 feet if
the airport has any runway that is longer than 3200 feet, a 50:1 slope out
to 10,000 feet if all runways on the airport are no longer than 3200 feet
and a 25:1 slope out to 5,000 feet for heliports).

In addition, Section 17.7(c) requires notification, when requested by the
FAA, for tower construction (or alteration) in an instrument approach area
when "available information indicates it might exceed an obstruction
standard of the FAA."  This is not as straightforward as the other
requirements, since the instrument approach area obstruction requirements
may be unique to each airport and approach.  However, the FAA standards
governing approach procedures and airport clearance zones may provide
general guidelines (this would cover the "clear zones" immediately adjacent
to the runways that you recall).  If anyone is interested, I'll try to
locate the appropriate FAA references.

Part 17 may be found online at
http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr17_04.html.

Larrie Sutliff  W2UL




> As I recall, there is a clear zone right off
> the end and then it goes to a 20:1 slope which starts at the end of the
> runway. Beyond some specific distance it goes to 100:1 up to 5 miles from
> the end of the runway.  I've been trying to find these distances and
ratios
> in the FARs or AIM, but nothing so far.  We have 2 and 3 story houses
within
> a city block off the south end of 18/36 at 3BS.