Today I would like to talk to you about flying boats. But first I would like to ask you a question. Are you believe?
It is the dream of every man to own a boat. And it is the dream of every man to own an aeroplane. And some men dream that they are a fly. It is therefore a curious thing that so few men own flying boats. Many people believe that men rule the world. This is not the case. The flying boat is proof that men do not rule the world. It is proof that men are ruled.
Flying boats emerged about ten years after Orville and Wilbur Wright's first aerial jaunt, with the most advanced developments coming from early aviation mogul Glenn Curtiss. The Wrights had tried experimentally fixing a canoe to one of their early fliers, but Curtiss was the first person to put his back into the idea. He hoped that the US Navy might have a use for his machines, and in 1910 a Curtiss biplane became the first aircraft to take off and land from a ship. In 1913 Curtiss designed a flying boat to fly across the Atlantic Ocean, but the attempt was scuppered by the outbreak of World War One. Nonetheless, variations of the machine sold to the US Navy and Britain's Royal Navy. One of the British modifications, the Felixstowe F.2A, was even sold back to the US and built under licence as the Curtiss H-16. Curtiss' basic design had all the general characteristics of flying boats to come, albeit that it was a biplane with crew positions that were open to the elements. Nonetheless flying boats had come to stay, with a future as secure as that of the mighty airship. Flying boats could land on any body of calm water, and they could be bigger and heavier than aeroplanes that had to take off from bumpy grass fields. In the event of engine failure, a flying boat could gracefully set down on the sea. There was no danger of missing the runway. Flying boats performed reconnaissance patrols for the RN towards the end of the First World War, with a Royal Navy Curtiss H-12 shooting down a Zeppelin in May 1917.
Flying boats were hit by the same general technological slump that afflicted all aviation during the immediate post-war years. Aviation design in general was driven by military requirements, which were spartan during a time of economic depression and demilitarisation. The basic Curtiss design continued in service with the RN and US Navy until the end of the 1920s, by which time the demands of commercial airlines such as Pan Am and Imperial Airways were driving innovation. Despite the Great Depression, there was a market for luxury flying boats that could take very rich people from London to Cape Town, and during the 1930s flying boat design kept up with that of conventional aircraft. Canvas-covered biplanes became all-metal monoplanes, such as the Short S23 Empire and the upholstered Consolidated Commodore. These aircraft represented an intermediate step to the brief heyday of the flying boat, a period in which Pan Am flew very rich people off to Rio in "clippers". Only a few dozen of Pan Am's Clippers were built, spread across three models. The name originated with the Sikorsky S-40 and Sikorsky S-42, continued with the Martin M-130, and culminated with the Boeing 314. This latter plane was the largest passenger aircraft of any type in the world, the Airbus A380 of its day. Whereas the Martin M-130 flew across the Pacific, to the Philippines, Hong Kong, Hawaii and so forth, the Boeing 314 went straight for the jugular. New York to Southampton and Marseilles, across the Atlantic Ocean. The Boeing 314 entered service in 1938, at a time when the world's air forces were going mad for aeroplanes, any aeroplanes, as many aeroplanes as possible.
Flying boats flew and fought during the Second World War. Whereas only a few dozen of the luxury aircraft mentioned above rolled off the production lines, there were hundreds upon hundreds of Catalinas, Mariners, and Sunderlands, some of which continued in service up to the time of colour television. Some of the Clippers were pressed into service as high-level military transports, and in 1943 a Boeing 314 took President Roosevelt over the Atlantic, the first aeroplane trip by a serving US President. But the war used up the flying boat. The only post-war flying boat that most people could name is the Hughes H-4 "Spruce Goose", an enormous flying white elephant boat. Flying boats entered the jet age without fanfare and continue in civilian and military service in very limited numbers, but they are fading away.
Flying boats are subject to a number of design constraints that do not apply to conventional aircraft. Firstly, they must have a hull that is seaworthy and resistant to salt corrosion, and they must be strong enough to withstand the rigours of landing on water. The engines must be powerful enough not only to propel the flying boat through the air, but also to overcome the parasitic drag of taking off from the sea. This was the greatest early problem that faced Glenn Curtiss, and he solved it by building a "step" into the hull design, with the rear half of the hull higher than the front half. Once the flying boat reached a certain speed, the prow acted like a hydroplane, causing the boat to skim gracefully over the water.
Flying boats must have high-mounted wings, so that the engines do not become waterlogged. Several designs went so far as to mount the engines and wings up and away from the fuselage. A flying boat must have sufficient equipment to berth in littoral waters, with an anchor and a bilge pump, although the weight of this equipment can be partially offset by the fact that true flying boats do not require an undercarriage. However, a flying boat must have a means of keeping upright and level whilst in the water, and thus floats were usually mounted towards the ends of the wings, offsetting any weight saved by omitting an undercarriage, and furthermore creating drag whilst in the air. In general therefore a flying boat of a certain size and payload capacity is heavier, more complex, and more expensive than an equivalent land-based aircraft, and it will not fly as well.
Several flying boats went on to lead famous wartime careers, notably the Consolidated PBY Catalina, the most-produced flying boat of all time, and the graceful Grumman Goose. Each of the major naval combatants fielded at least one flying boat, such as Britain's Short Sunderland, Germany's Dornier Do 24, and Japan's Kawanishi H8K Emily. But the type was always under threat from conventional aircraft. The performance limitations were too great for flying boats to work as fighter aircraft, although there were a number of fighting floatplanes, such as the Heinkel He 115 torpedo bomber or the Arado Ar 196 scout plane. These designs came from a time when battleships and cruisers carried a handful of aircraft to use as scouts or torpedo bombers, and they were at a disadvantage when faced with less compromised carrier-borne aircraft.
Flying boats had significant operational limitations in other roles as well. It is hard to transfer a large body of troops to and from a fleet of seaplanes, and it is easier to marshal and maintain a squadron of aircraft on the ground than in the water. Flying boats might have found a niche in the airborne assault role during the Pacific campaign, but the distances and payloads involved favoured seaborne assault with maritime landing craft. Although flying boats are free to land wherever there is water, the realities of keeping a machine maintained and supplied with fuel ensured that flying boats were as tied to fixed bases as conventional aircraft.
The aircraft nonetheless found a niche in the anti-submarine and search & rescue roles. For a short time they were the only machines with sufficient range and payload to conduct lengthy maritime patrols. Flying boats were not used so much for their ability to take off and land from water, although this must have been a great comfort for the men who flew out over the North Sea. Instead, they were simply the largest and most capacious aircraft of the early war years, with the greatest payload capacity and internal fuel space. Britain's Sunderlands had an impressive combat record against U-boats, sinking twenty-six (twenty of which were unassisted), and scaring off scads of others. Nonetheless they were matched by plentiful Lockheed Hudsons and North American B-25 Mitchells, and eventually edged out by the long-range Consolidated B-24 Liberator. The Sunderlands petered out of British service during the 1950s, whilst the last British flying boat - the Short Solent - flew commercial routes in New Zealand until 1960. The immediate post-war Grumman Albatross remained in service with the US Navy until the late 1960s, and a few remain as passenger aircraft. The United States Coast Guard continued to use its Martin Mariners until 1958, the Argentine Air Force slightly longer. The Mariner's sequel, the Martin Mars, is still used commercially as a firefighter, with two bright red machines operating from Sproat Lake in British Columbia. In the 1950s Martin designed a jet-powered flying boat, the Martin Seamaster, but the US Navy did not bite, and Martin subsequently left the aircraft business. Curtiss had similarly given up on aircraft after the Second World War. The Japanese ShinMaywa PS-1 was designed as late as 1966 for anti-submarine duties, although it served in limited numbers and was eventually replaced by the conventional Lockheed Orion.
If radar had been introduced ten years before it was, flying boats might have excelled in the maritime airborne early warning role. Although the fixture of downwards-pointing radar was tricky on a flying boat, most ended the war sporting some kind of radar, with bulky radomes or spiky antennae such as on the enormous Blohm und Voss Bv 222 "Wiking". As things turned out, the advent of radar coincided with the development of long-range conventional bombers, which would provide the basis for subsequent radar patrol aircraft. The war also saw the aircraft carrier become the dominant naval vessel, and with it the flying boat lost whatever remaining utility it possessed. Compact conventional aircraft could provide close AEW and anti-submarine support for carrier groups, whilst helicopters would eventually perform search & rescue missions just as well as the flying boats. The popular Sikorsky S-61 "Sea King" helicopter could even land on the water, in dire emergency, making it perhaps an honorary flying boat.
Of course, a land-based aircraft cannot land on water at all, but after the Second World War there was no longer a reason for passenger aircraft to land on water. There were plenty of large, flat, concrete runways dotted around all over the place, and there was a superfluity of former military transport aircraft to fly from them. Apart from the performance disadvantages, this is the reason most commonly given for the decline of the flying boat. Flying boats can only justify their existence if they take off or land from water, and although most of the world's great cities are also ports, there are many routes that a flying boat simply cannot fly. This nonetheless raises the possibility of a parallel world in which the world's major airports are instead giant artificial lakes, and Southampton on the south coast of England is a thriving international terminus. Which it is not. Nonetheless, during the Berlin Airlift, British Short Sunderlands ferried food by landing on the slow-moving Havel river.
A few flying boats were designed in the post-war era. ShinMaywa of Japan produces the US-1, an upgraded search & rescue variant of the aforementioned PS-1. The Beriev bureau in Russia specialised in the type after WW2, most notably with the giant Be-42 of the 1980 and 1990s. It currently produces the jet-powered Be-200 for transport and firefighting (another niche that suits the flying boat, as it can replenish its water tanks from any sizeable body of water). The Canadian company Canadair also manufactures a firefighting flying boat, the CL-415. And there are a number of companies that sell hang-gliders which float with underslung dinghies, or dinghies which fly with overhead hang-gliders, depending on your outlook, although these machines look comical and no-one lusts after them. The Boeing 314 makes men feel more manly, whereas hang-gliding dinghies are objects of fun.
And that is how the flying boat came to be, and to be not.
Laurence K. Loftin, Jr
"Quest for Performance: The Evolution of Modern Aircraft":
Greg Goebel's Air Vectors, particularly the pages on the Short Sunderland, Shin Meiwa US-1, Martin Mariner, and Martin Seamaster:
UBoat.net's pages on the various anti-submarine aircraft that fought in WW2:
"Eugene Ely's Flight from USS Birmingham"
The US Centennial of Flight Commission's page on Curtiss' early flying boats: