Floatplane - Design

Design

Floatplanes have often been derived from land-based aircraft, with fixed floats mounted under the fuselage instead of retractable undercarriage (featuring wheels).

All floatplanes tend to be less stable on water than flying boats. However, in small aircraft design, floatplanes offer an advantage over flying boats, as the hull (i .e. the lower part of the fuselage) of floatplanes does not make contact with water surfaces, permitting a conventionally-mounted single piston engine, with a propellor, in the nose.

Floats inevitably impose extra drag and weight, rendering floatplanes slower and less manoeuvrable during flight, with a slower rate of climb, relative to aircraft equipped with retractable landing gear. Nevertheless, air races devoted to floatplanes attracted a lot of attention during the 1920s and 1930s, most notably in the form of the Schneider Trophy.

There are two basic float configurations on floatplanes:

• "single float" designs, in which a single large float is mounted directly underneath the fuselage, with smaller stabilizing floats underneath the wings and;
• "twin float" designs, with one float mounted beneath each wing.

The main advantage of the single float design is its capability for landings in rough water: a long central float is directly attached to the fuselage, this being the strongest part of the aircraft structure, while the smaller floats under the outer wings provide the aircraft with good lateral stability. By comparison, dual floats restrict handling, often to waves as little as one foot (0.3 metres) in height. However, twin float designs facilitate mooring and boarding, and – in the case of bombers – leave the belly free to carry a large bomb or torpedo.