Section 108.241 - Visual aids(a) Each helicopter deck must-(1) Have a wind direction indicator located in an unobstructed area readily visible to helicopter pilots approaching the deck;(2) Be fitted around the perimeter with yellow and blue lights in alternate order, not more than 3 meters (10 ft.) apart; and(3) Be marked with- (i) The unit's identification;(ii) A continuous line 40 centimeters (16 in.) wide on the perimeter; and(iii) Aiming circles as may be appropriate considering deck configuration, helicopter type, and operational requirements.(b) All markings must be in a contrasting color to the surface of the deck.