The Navigation Rules specify lights that must be displayed on vessels underway from sunset to sunrise, and in daylight during times of restricted visibility. There are “Inland” and “International” Nav Rules, which are similar for the most part, but do include a few differences. The U.S. Government Printing Office publishes the Navigation Rules, which are available at most marine stores.
Light requirements for pleasure and commercial vessels under the inland and international rules are complex, given the various sizes and activities of vessels. We will discuss the requirements for lights on 40′ power and sailing vessels used for pleasure. While there are some exceptions for smaller vessels, most are outfitted with lights required for 40′ vessels. Your understanding of light requirements is important if you are to avoid collisions and other mishaps.
There are three basic types of lights for pleasure boats underway. The first is the “masthead light”. It is always white with an arc of visibility of 225 degrees and faces forward. It is required on both power and sailboats while they are underway and propelled by machinery. Sailing vessels, while under sail without auxiliary power, do not display a masthead light.
“Sidelights” are red on the port side and green on the starboard side. They have an arc of visibility of 112.5 degrees each and illuminate an area from the forward/aft centerline to the port side (red) and starboard side (green). They are required on both power and sailboats while they are underway, whether propelled by sail or machinery.
Notice that the combined arc of sidelights (112.5 degrees each) is equal to the arc of a masthead light (225 degrees). If your masthead light and sidelights are properly installed, at least one sidelight will be visible along with your masthead light. If your boat is on a collision course with another vessel, both your red and green sidelights will be visible to the other vessel operator at the same time. Should you alter course to port or starboard, only one sidelight will be visible by the other vessel since sidelights show from the forward/aft centerline to port (red) or starboard (green).
A “Sternlight” is always white with an arc of visibility of 135 degrees and faces aft. It is required on both power and sailboats while they are underway, whether propelled by sail or machinery. Note that the 135 degree sternlight and the 225 degree masthead light add up to 360 degrees. If your lights are properly installed, your masthead light and sternlight will not be visible at the same time, but one of them will always be visible while you are under power.
When you see only a red or green sidelight, you will be looking at a vessel under sail. When you see a masthead light in conjunction with a sidelight, you will be looking at a vessel under power. When you see both red and green sidelights at the same time, the vessel is on a collision course with you. These lights tell you something about “direction” and “propulsion.” A mariner that understands light requirements can view another vessel’s lights and make informed decisions about safe passage. The Nav Rules book has many good illustrations that accompany the text. We highly recommend having a copy on board.
Until next time, we wish you clear skies, fair winds and calm seas!
World Wide Marine Training, LLC, is a U.S. Coast Guard Approved facility authorized to give examinations for captain’s licenses up to Master 200 Tons, Able Seaman up to Unlimited, STCW Basic Training, Radar, ARPA and other Endorsements. Please visit www.worldwidemarinetraining.com or call toll-free 866-249-2135.