The amphibious airplane offers unparalleled utility. It also provides for a greater measure of safety than the conventional land airplane. The amphibious airplane is designed to operate from rough airports and available waterways, with or without prepared surface, docking or handling facilities. It is also well suited for operation in remote and undeveloped areas as well as operation in the downtown area of major cities, most of which have sufficient water available for a suitably designed amphibious airplane. After landing on water, the amphibious airplane can taxi onto the adjacent land for boarding and unloading passengers and servicing in the manner of a conventional airplane.
While in transit, every river, pond or lake over a half mile long having reasonably calm water with waves of about two feet or less is an emergency landing field, as are the usual fields and smaller airports. Furthermore, the hull bottom of amphibious airplanes, which are generally stronger than the bottom of the conventional airplane fuselage because of the design requirements of water landing loads, offers more protection in the event of a forced landing.
Despite these enormous advantages, the amphibious airplane does not enjoy any measure of utilization today. Higher initial costs, higher operating costs and generally poorer performance in terms of speed, payload and range have made them unattractive relative to conventional airplanes. This situation exists because of several persistent problems related to the design of amphibious airplanes.
One problem is greater weight because of increased hull structural strength required to absorb the high loads of water landings, which increase substantially with the higher landing speeds generally associated with high performance airplanes. The wings of high performance airplanes are usually designed for the high speed, high altitude flight regime requirements rather than the low speed take-off landing requirements and therefore the high performance airplanes have high stalling speeds and thus high landing speeds. This increased structural weight requires greater engine power, which, in turn, increases the weight still further with the result of both larger initial costs and operating expense. Furthermore, increases in weight and aerodynamic drag result from the traditional V-shape hulls required to absorb the high landing loads, the transverse step required for water take-off, the wing tip floats usually required for transverse stability in the water or the poorly designed hull tunnel of those airplanes using sponsons for transverse stability instead of floats, and the landing gear either hanging in the airstream or stowed in an unsatisfactory manner.
Convertible amphibious aircraft are often used in areas where it may be necessary to land on water or on land as desired. The aircraft have landing gear or wheels which are extended when landing or taking off of land-based runways. For water landings, the landing gear is retracted. In flight, the landing gear is retracted to reduce air drag. Thus, there is not a right or a wrong retractable gear position for landing or takeoff. However, a convertible amphibious aircraft upon takeoff or landing from a land-based runway must have its retractable landing gear in a down position as with any aircraft.
A convertible amphibious aircraft must also, however, take off from water when its landing gear is folded within the fuselage, wings or pontoons. In these instances the landing gear is left in the retracted position during flight and never extended during that flight if, in fact, the flight terminates with another water landing.
On the other hand, an amphibious aircraft might takeoff from a water-based landing strip with its gear in the retracted position, leave the gear in the retracted position during the flight and then travel to a land-based runway. Serious injury to the occupants of the plane and extensive damage to the convertible amphibious plane occurs if a landing is attempted with the landing gear in an improper position for the landing surface. This risk is continually present, especially if the plane's route varies somewhat randomly between water-based and land-based runways. This is often the case if the pilot is stopping at a land-based runway, while the next stop on the pilot's itinerary might be a canal, river or lake. This problem is particularly seen in coastal areas where commercial activity is of a marine nature. Such a pilot might be landing at municipal airports which are land-based yet in the next few minutes may be landing aside work boats, barges, offshore oil platforms, or even a customer's facility which might have no landing strip but rather a dock for boats and seaplanes to approach for loading and unloading of personnel, cargo, and the like.
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