Ramps vary widely in size, shape, and construction materials, e.g. from rough logs only slightly wider than the aircraft floats to wide inclines covered with heavy-duty steel and/or concrete structures. The simplest ramp consists of a wood plank platform approximately 15 by 20 feet (5 m by 6 m) laid on a sloping shore, with half of its length in the water thereby permitting a small float plane to taxi up and out of the water.
a. Location. A minimum of 100 feet (30 m) of unobstructed water should be available directly
offshore from the ramp, in the direction from which approaches are normally made.
b. Design Concept.
Ramps are of fixed or hinged type construction. Fixed ramps are usually weighted down or attached to a fixed in-water footing at the toe, and secured to a stable on-shore structure such as a seawall at the other end. Hinged ramps are allowed to
rise and fall with the water by means of a hinge on the shore end, while the toe end is buoyed at a predetermined depth. Fixed ramps are more common, but become relatively costly in shallow areas or where the water level variation exceeds 8 feet (2.5 m). Piling or piers are
commonly used to support the stringers of fixed ramps.
c. Slope. The slope of a ramp should not be greater than 6:1, with flatter slopes ranging to 10:1 being desirable. Slopes flatter than 10:1 are usually too long and costly to construct. Ramps intended to serve tri gear amphibians should not be steeper than 8:1 since, with steeper slopes, the hull of some amphibians may drag on the ramp as the craft enters the water.
d. Depth. A 4 foot (1.2 m) depth of toe will provide sufficient clearance for most waterborne aircraft. A 3 foot (1 m) depth will accommodate all but the heaviest types of amphibians. An 18 inch (45 cm) depth is adequate for small, light float planes. In all cases,
depth dimension should be established based on the low water level datum in that locality.
e. Width. A ramp width of 30 to 40 feet (9 to 12 m) will accommodate aircraft in most wind, current, and tidal conditions. 15 feet (4.5 m) is the minimum ramp width required for small twin-float or amphibious aircraft operation when water and wind conditions are
relatively calm. Practically all light waterborne aircraft can be handled easily, and pilots of small seaplanes can make an unattended ramp approach under adverse
conditions, if 5 feet (1.5 m) is added to this minimum width.
f. Decking. Decking can be laid diagonally or at right angles to the line of travel. Planks should be placed rough side up, and have a .5 inch (1.3 cm) space between each plank. When laid at right angles to the line of travel, the up-ramp edge of each plank may be raised
no more than 1 inch (2.5 cm) to permit the hull of the plane to slide easily and still provide good footing for people walking on the ramp. All bolts, nails, and spikes used to attach the decking should be countersunk to avoid damage to floats or tires.
Qualty,Safety and Training