Washington Administrative Code › Title 468 - Transportation, Department of (See Title 88) › Chapter 468-240 - Obstruction marking and lighting › LIGHTING › Section 468-240-105 - General

Current through Register Vol. 24-14, July 15, 2024
(1) The purpose of lighting an obstruction
				which presents a hazard to air commerce is to warn airmen during the hours of
				darkness and during periods of limited daytime light intensity of the presence
				of such an obstruction. To accomplish this objective, it is necessary to
				provide adequate lighting on the obstruction in a manner which assures
				visibility of such lighting from aircraft at any normal angle of approach. In
				determining the proper amount of obstruction lighting to adequately mark an
				obstruction, the mean elevation of the top of the building in closely built-up
				areas may be used as the equivalent of the ground level.
(2) The top light, or lights, displayed on an
				obstruction should be installed so as to mark the points or edges of the
				obstruction highest in relation to an obstruction determining surface, except
				that when no obstruction determining surface is involved, such top light, or
				lights, should be installed on the points or edges of the obstruction highest
				in relation to the ground, or water if so situated. If two or more edges of an
				extended obstruction located near a landing area are of the same height, the
				edge nearest the landing area should be lighted.
(3) When the upper part of only a portion of
				a building or similar extensive object projects above an obstruction
				determining surface, that portion only need be obstruction lighted and the
				point or edge of it highest in relation to the obstruction determining surface
				should be regarded as the "top of the obstruction." In certain cases, however,
				such as when the obstruction determining surface concerned is an approach or
				transition surface (i.e., sloping) this point or edge highest in relation to
				the obstruction determining surface may not be the highest above a horizontal
				plane passing through the base of the object. In such cases, additional
				obstruction lights should be placed on the highest part of the object as well
				as on the point or edge highest in relation to the obstruction determining
				surface.
(4) If a light, or lights,
				which is installed on an obstruction is shielded in any direction by an
				adjacent object, additional lights should be mounted on that object in such a
				way as to retain the general definition of the obstruction, the shielded light,
				or lights, being omitted if it does not contribute to the definition of the
				obstruction.
(5) Obstruction lights
				and hazard beacons should be operated at all times when the center of the sun's
				disc is 6° or more below the horizon and during periods of restricted
				visibility. They may also be operated at such other times as considered
				desirable. For the purpose of this standard, the term "sunset to sunrise" shall
				be generally regarded as that period when the center of the sun's disc is
				6° or more below the horizon.
Statutory Authority:
					 Chapter
					 47.68 RCW. 96-17-018
					 (Order 164), recodified as § 468-240-105, filed 8/13/96, effective
					 9/13/96; O.M.&L. standards (part), filed
					 9/13/61.