Designing, And Constructing Seaplane Base Facilities CHAPTER 3  



Most large bodies of water provide adequate length and width for seaplane operations. Where the available water surface is limited a turning basin may be needed to separate aircraft from other surface craft activity.


A water operating area at least 2,500 feet (750 m) by 200 feet (60 m) is recommended. This size will accommodate a sea lane 2,500 feet (750 m) by 100 feet (30 m) with 200 foot (60 m) diameter turning basins at each end. Although a depth of 6 feet (1.8 m) is preferred, a minimum depth of 3 feet (1 m) is adequate for single engine operations. The length of the water operating area needs to be increased by 7 percent per 1000 feet (300 m) of elevation above sea level to compensate for the change in density altitude.


A taxi channel for small seaplanes should have a minimum width of 125 feet (38 m), although a width of 150 feet (45 m) or more is desirable. The channel should provide direct access to the on-shore facility and, when possible, should be oriented so the approach to the ramp or float will be into the prevailing wind or current. A minimum clearance of 50 feet (15 m) should be provided between the side of the channel and the nearest obstruction.


a. Location. Turning basins may be required where use of the water surface is restricted. A minimum radius of 200 feet (60 m) is recommended. A turning basin should be located adjacent to the shoreline facility and at each end of the water operating area.

b. Clearance. The stronger the wind, the more room it takes to make a turn. A minimum clearance of 50 feet (15 m), should be provided between the side of the turning basin and the nearest obstruction.

a. Background. Anchorage areas should provide maximum protection from high winds and rough water. They should be located in a manner that will permit unrestricted maneuvering of the aircraft when approaching the buoys. The anchorage area should be within sight and calling distance of a floating dock or ramp. The size is determined by the number and size of aircraft to be accommodated. Anchorage areas must satisfy the need for aircraft to turn into the wind as they swing on their moorings.

b. Space Required. The space required is determined by aircraft length and wing span, the length of line and bridle, and the lowest water level in the anchorage area. The length of anchor line "A" (Figure 3-1) should be six times the maximum depth at mean high water. Where aircraft swing is limited, the length of anchor line may be shortened to not less than three times the water depth, provided the normal anchor weight or holding capacity is doubled.

c. Center-to-Center Spacing. Center-to-center anchor spacing, "B", for small twin float aircraft mooring, should not be less than twice the length of the longest anchor line plus 125 feet (38 m). For larger aircraft, including flying boats and amphibians, an additional 100 feet (30 m) should be added to this spacing. Figure 3-1 shows a general layout of an anchorage area. Anchor capacity and spacing may be influenced by bottom condition and type.

d. Shear Boom. A shear boom should be considered if seaplanes are to be moored in an area where the current is strong. A shear boom consists of a series of logs tied together at their ends and anchored. Its function is to deflect debris away from the seaplane floats, as well as to create an area of calm water on the downstream side.


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