Water towers, grain elevators, gas holders and similar obstructions should be lighted in accordance with the following specifications:

(1) Specification "G-1." When the particular obstruction is not more than 150 feet in over-all height above ground, or water if so situated.

(a) There should be installed at the top of the obstruction at least two lights, each light consisting of a lamp of at least 100 watts, enclosed in aviation red obstruction light globes. These lights should burn simultaneously and should be positioned so as to insure unobstructed visibility of at least one of the lights from aircraft at any normal angle of approach.

(2) Specification "G-2." When the particular obstruction is more than 150 feet but not more than 300 feet in over-all height above ground, or water if so situated.

(a) There should be installed at the top of the obstruction a flashing 300 mm electric code beacon equipped with two lamps and aviation red color filters. The two lamps of the beacon should burn simultaneously and each should be at least 500 watts. The beacon should be positioned so as to insure unobstructed visibility of it from aircraft at any normal angle of approach.

(b) At the approximate midpoint of the over-all height of the obstruction, there should be installed three or more lights, each light consisting of a lamp of at least 100 watts, enclosed in aviation red obstruction light globes. The position of these intermediate lights on the vertical plane should be as close to an equidistant level between the top beacon and the ground level as the particular shape and type of construction of the obstruction will permit. These lights should be placed at regular intervals on the horizontal plane in a manner to insure unobstructed visibility of at least two of the lights from aircraft at any normal angle of approach.

(3) Specification "G-3." When the particular obstruction is more than 300 feet but not more than 450 feet in over-all height above ground, or water if so situated.

(a) There should be installed at the top of the obstruction a flashing 300 mm electric code beacon equipped with two lamps and aviation red color filters. The two lamps of the beacon should burn simultaneously and each should be at least 500 watts. The beacon should be positioned so as to insure unobstructed visibility of it from aircraft at any normal angle of approach.

(b) At approximately two-thirds and one-third of the over-all height of the obstruction there should be installed three or more lights, each light consisting of a lamp of at least 100 watts, enclosed in aviation red obstruction light globes. The position of these intermediate lights on the vertical plane should be as close to equidistant positions between the top beacon and the ground level as the particular shape and type of construction of the structure will permit. These lights should be placed at regular intervals on the horizontal plane in a manner to insure unobstructed visibility of at least two lights on each level from aircraft at any normal angle of approach.