Glossary of Aviation Terms | Floats

Floats | Paramount Business Jets

Floats are slender pontoons mounded under the fuselage of float planes (a type of seaplane). In normal operations, only the floats of a float plane come into contact with water, and the fuselage remains above the water. Unlike flying boats, which use their fuselage for buoyancy, float planes rely solely on the buoyancy of their "floats" to keep the aircraft afloat on the water.

Floats are essentially a straightforward development of land-based aircraft gear, as floats are mounted under the fuselage instead of wheels. The development of floats made float planes more popular than flying boats for small aircraft designs since it allowed a single piston engine to be installed at the nose of the fuselage rather than high above the fuselage. Due to their proximity to the water surface, flying boats could not have engines installed near the nose of the aircraft. Despite this, floats that are mounted underneath the fuselages of aircraft inevitably impose extra drag and weight on float planes, which eventually renders them less maneuverable during flight than ground-based aircraft.

Floats on float planes can be arranged in two different ways. One is a single float design in which a single large float is mounted directly underneath the fuselage, with smaller stabilizing floats underneath the wings. The other design is a twin float design in which a pair of floats are mounted beneath the wing roots in place of wheeled landing gear. Single float designs are often advantageous to float planes as they are able to handle rough seas due to the variety of large and small floats on the aircraft, which provides good lateral stability during landing in rough seas. Despite this, the twin float design facilitates both mooring and boarding, and allows military float planes to carry a torpedo or a large bomb load.