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Quest for Performance: The Evolution of Modern Aircraft


Part I: THE AGE OF PROPELLERS


Chapter 8: Boats in the Sky


Background



[163] Seaplanes are aircraft designed to take off and land on the surface of the water. Aircraft of this type fall into two distinctly different categories. One category consists of conventional land planes that are mounted on floats, sometimes called pontoons, in place of a conventional landing gear with wheels. The other category consists of a basically different type of aircraft in which the lower part of the fuselage is shaped somewhat like a boat and which, at rest and low speed, floats on the surface just as a boat does - hence the term "flying boat."

From its inception and early demonstration by Glenn H. Curtiss in 1912 until a few years after the end of World War II, the flying boat was a key element of commercial and military aviation throughout the world. Large-scale commercial operations ceased 2 or 3 years after the war, but military use of the flying boat continued in the United States until the last squadron of these picturesque aircraft was decommissioned in 1967. No large flying boats have been built in the United States since 1960; however, both Japan and the Soviet Union produce such aircraft in limited numbers for military purposes, and a flying boat is still built in Canada for use as a water bomber in fighting forest fires.

The popularity and apparent demise of the flying boat as an important element of aviation can be traced to a combination of operational, performance, and economic characteristics. In the years prior to World War II, airports capable of handling large, long-range aircraft were few in number and nonexistent in most parts of the world, particularly in undeveloped nations. Most areas of the world that are of interest for trade and commerce, however, are located near bodies of water such as lakes, rivers, harbors, inlets, and other types of marine facilities. These natural resources, which require little if any development, provided an abundant and almost unlimited number of worldwide [164] facilities for the operation of large, long-range flying boats. Both military and commercial air operations made extensive use of these natural resources. Airlines operated both passenger and freight service with flying boats, and the military used these aircraft for reconnaissance, antisubmarine patrol, search and rescue, and other activities. In the absence of any permanent ground facilities, naval flying boats could operate for weeks in the most forbidding geographical areas while supported by a small ship called a seaplane tender. In addition, the flying boat seemed to offer on long over-water flights the prospect of a safe landing in the event of an engine failure, a very real possibility with the relatively unreliable engines available in the early days of aviation. The chances of a flying boat surviving a landing in rough seas on the open ocean were, of course, problematical; this advantage was perhaps more psychological than real. Yet, a number of cases have been recorded in which passengers and crew survived a landing in the open ocean after engine failure.

For all these reasons, the flying boat seemed for many years to have an important and permanent place in the aeronautical world. The flying boat, however, possessed certain disadvantages inherent in its dual capacity for operation on the water as well as in the air. The aerodynamic drag of the hull-fuselage was basically higher than that of the conventional fuselage of a landplane. Hence, the cruising speed tended to be lower than that of a comparable landplane, as was the aerodynamic cruising efficiency expressed by the maximum lift-drag ratio. The economic potential of the flying boat was accordingly limited in comparison with the landplane. Further, the ever-present danger of collision with submerged objects in the water and subsequent hull rupture and possible sinking, as well as difficulties in passenger handling to and from a moored flying boat, posed ever-present operational problems.

During World War II, many parts of the world saw the development of a large number of airports equipped with long, hard-surface runways. Large, fast, highly efficient landplanes suitable for carrying passengers and equipped with four reliable engines also emerged from the war. These two factors spelled the end of the flying boat as a viable means for the economical transportation of passengers and freight over long distances. Pan American Airlines, a pioneer in the use of flying boats on long over-water routes, terminated operation of this type of aircraft in April 1946, less than a year after the end of the war. Today, a few small flying boats built prior to World War II are still used in [165] inter-island commuter-type operations. One small, four-place sport flying boat is still in limited production in the United States at the present time. For many years after the war, the U.S. Navy and Coast Guard continued to use flying boats for reconnaissance, antisubmarine patrol, and search-and-rescue missions. Long-duration turboprop landplanes and helicopters, however, gradually took over these duties and finally completely replaced the flying boat.

The technical evolution of the flying boat from 1914 to 1960 is briefly described below. Photographs of 21 representative flying boats are used to illustrate the development of this type of aircraft, and their physical and performance characteristics are presented in table IV (appendix A). The references used in compiling these characteristics are contained in the reference list at the end of this book, and the specific references employed for each aircraft are cited in the table. Some additional references dealing with flying boats not specifically cited in the tables are included in the reference list. Reference 80, for example, presents an interesting historical survey of the flying boat in the United States. As mentioned, primary emphasis in this book has been placed on aircraft originating in the United States. This has been done to limit the scope of material and is in no way intended as an adverse reflection on the many excellent flying boats developed in other countries.