23.1399—Riding light.
(a)
Each riding (anchor) light required for a seaplane or amphibian, must be installed so that it can—
(1)
Show a white light for at least two miles at night under clear atmospheric conditions; and
(2)
Show the maximum unbroken light practicable when the airplane is moored or drifting on the water.
(b)
Externally hung lights may be used.