Chart Navigation & Plotting · Aids to Navigation
A light characteristic listed as 'Fl R 4s' means:
- AFixed red light, 4 feet high
- BFlashing red, one flash every 4 seconds✓ Correct
- CFour red lights in a vertical line
- DRed light visible for 4 miles
Explanation
'Fl R 4s' = a flashing red light with a period of 4 seconds (the full cycle, light plus eclipse, repeats every 4 seconds). The color follows the abbreviation and the period is the time for one complete cycle.
Authority: USCG Light List; Chart No. 1
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