No person is required to notify the Administrator for any of the
following construction or alteration:
(a) Any object that would be shielded by existing structures of a
permanent and substantial character or by natural terrain or topographic
features of equal or greater height, and would be located in the congested
area of a city, town, or settlement where it is evident beyond all
reasonable doubt that the structure so shielded will not adversely affect
safety in air navigation.
(b) Any antenna structure of 20 feet or less in height except one that
would increase the height of another antenna structure.
(c) Any air navigation facility, airport visual approach or landing
aid, aircraft arresting device, or meteorological device, of a type
approved by the Administrator, or an appropriate military service on
military airports, the location and height of which is fixed by its
(d) Any construction or alteration for which notice is required by any
other FAA regulation.