Amphibious aircraft

Fixed-wing amphibious aircraft are seaplanes (flying boats and floatplanes) which are equipped with retractable wheels, at the expense of extra weight and complexity, plus diminished range and fuel economy compared with planes designed specifically for land-only or water-only operation.

These aircraft, and those designed as floatplanes with a single main float under the fuselage centerline (such as the Loening OL and Grumman J2F), require outrigger floats to provide lateral stability so as to avoid dipping a wingtip, which can destroy an aircraft if it happens at speed, or can cause the wingtip to fill with water and sink if stationary.

This can provide the needed stability, while floatplane amphibians usually avoid the problem by dividing their buoyancy requirements between two floats, much like a catamaran.

In the United Kingdom, traditionally a maritime nation, a large number of amphibians were built between the wars, starting from 1918 with the Vickers Viking and the early 1920s Supermarine Seagull, and were used for exploration and military duties, including search and rescue, artillery spotting and anti-submarine patrol.

These evolved throughout the interwar period to culminate in the post–World War II Supermarine Seagull, which was to have replaced the wartime Walrus and the Sea Otter but was overtaken by advances in helicopters.

The Grumman Corporation, latecomers to the game, introduced a pair of light utility amphibious aircraft – the Goose and the Widgeon – during the late 1930s for the civilian market.

In any case, few designs saw more than limited service, as there was a widespread preference for pure flying boats and floatplanes, due to the weight penalty the undercarriage imposed.

Amphibious aircraft have been particularly useful in the unforgiving terrain of Alaska and northern Canada, where many remain in civilian service, providing remote communities with vital links to the outside world.

Despite the gains of amphibious floats, small flying-boat amphibians continued to be developed into the 1960s, with the Republic Seabee and Lake LA-4 series proving popular, though neither was a commercial success due to factors beyond their makers' control.

Many today are homebuilts, by necessity as the demand is too small to justify the costs of development, with the Volmer Sportsman being a popular choice among the many offerings.