Many tower owners may be in violation of the “Nesting Rule” by blocking their beacon with new antennas, according to Randy Doremus, President and Owner of Dakota Lighting Supply.

The rule states:
“Nesting of Lights. Care should be taken to ensure that obstruction lights do not become blocked or “nested,” as new antennas, hardware, or appurtenances are added to the top of a structure. If new equipment is added that blocks the obstruction light’s visibility, the light fixtures must be relocated and/or raised so that it is not blocked by the new equipment. For example, when new larger cellular antenna panels are fitted to older towers, the obstruction light will need to be raised so that it is not blocked by the larger antenna panels. The widest structure, appurtenance, lightning rod, or antenna that can be placed in front of an obstruction light (excluding the L-810 light) without significantly blocking the obstruction light’s visibility should be no wider than 7/8 of an inch. Due to their smaller size, L-810 lights should not be blocked by any structure.”

• FAA Rule 10/8/2016 AC 70/7460-1L CHG 1

Doremus advises If you think you may be in violation of the rule, a possible solution is fitting the beacon to an adjustable extension that will take it above the obstruction.