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ShinMaywa’s US-1A, cleansed of the corrosive sea after every mission, continues an ancestral line of flying boats. (Tim Wright)

Giant Amphibian

Japan has one godzilla of a seaplane

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ON A COLD DAY IN JANUARY 1992, U.S. AIR FORCE CAPTAIN JOHN DOLAN ejected from his damaged F-16 at 25,000 feet and landed in the Pacific Ocean about 700 miles from the Japanese mainland. For the next four hours Dolan lay in a tiny rubber life raft that was tossed and continually swamped by high seas; he eventually suffered severe hypothermia. Finally, when he was barely conscious, Dolan saw a large, four-engine aircraft—a ShinMaywa US-1A bearing the Rising Sun of the Japanese military—slowly circling his raft.

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Aboard the US-1A, a radar at the copilot’s station indicated that the waves below were just over nine feet high. US-1A Pilot Commander Hideki Kida put the 50-ton aircraft down in the churning ocean and taxied to within 50 yards of Dolan’s raft. Two rescue swimmers got to Dolan and hauled him aboard the US-1A, and in another four hours Dolan was at the military hospital at Yokota Air Base, Japan.

With this rescue, one of 628 flown by a US-1A since it entered service in 1976, the aircraft completed for the first and only time the mission it was created to fulfill: rescuing military fliers. In its years of service, the US-1 type, with its 12-member crew, has made its real impact by saving civilians. To sailors at sea and people living on remote Japanese islands, it has been an aerial lifeline, an odd role for an aircraft that started out hunting submarines.

The US-1A began life as the ShinMaywa PS-1, an anti-submarine aircraft that first flew on October 5, 1967. A Japanese-designed and built flying boat, the PS-1 tracked submarines with a dipping sonar—an acoustic device lowered into the ocean—and was armed with torpedoes, depth charges, and five-inch rockets. The massive underwater microphone was so large that crew members could barely squeeze past when it rested inside the aircraft.

On a typical anti-sub mission, the PS-1 crew would range over hundreds of square miles of ocean, landing 12 to 16 times. At each landing, the crew, like fishermen lowering a hook, would submerge the sonar, trying to catch the fleeting sounds of an enemy submarine.

ShinMaywa built 21 PS-1s, which served the Japanese Marine Self Defense Force until 1980, when Japan chose a different aircraft for anti-submarine missions. Lockheed’s P-3C Orion was faster than the PS-1, had a longer range, and deployed a series of floating sonar-emitting buoys that could weave a tighter web around a submarine. It was also easier to maintain and more comfortable for its aircrew. It wasn’t long before the PS-1 was looking for a new mission and found one in the most unlikely place: the P-3C Orion.

With its 2,700-mile range, the P-3C ventured into stretches of the Pacific far from the home islands, and it seemed prudent to the Japanese defense force to have a rescue craft available in case an aircraft was lost in an area outside customary shipping routes. So the PS-1 shed its sonar, rockets, and torpedoes and was reborn as the US-1 rescue aircraft. Its primary mission: to rescue P-3C aircrews. In the process of rebirth, the new US-1 evolved from a true flying boat into an amphibian. ShinMaywa engineers replaced the flying boat’s beaching gear, with which it could roll onto a prepared shore under its own power, with sturdy landing gear, which could support a 50-ton aircraft landing on a runway at about 75 mph.

In the years after World War II, most countries abandoned the concept of large flying boats as patrol craft, but ShinMaywa’s history kept it focused on the type. The company traces its beginnings to 1918, when it was known as Kawanishi. It developed a line of floatplanes and flying boats that helped tie the Japanese empire together in the years leading up to World War II. By the end of the war, Kawanishi had built 2,862 aircraft. The most famous were a single-engine fighter known by the Allies as the “George” and two fourengine flying boats, the H6K “Mavis” and H8K-2 “Emily.” The Emily had a 124-foot wingspan (nine feet longer than that of the British Short Sunderland and 21 feet longer than a Boeing B-17’s), and, with a range of 4,500 miles, it has won accolades from aviation historians as the most advanced flying boat of the war.

The U.S. Navy was impressed enough with the Emily to have transported one after the war for testing at its Patuxent River facility in Maryland. Surface tests were conducted in the Chesapeake Bay, but engine failures brought the testing to a premature close, and the aircraft was exiled to the Norfolk Naval Air Station in Virginia, where it was wrapped in plastic and relegated to the station’s lost and forlorn. By then, it was the last known Emily in the world. In 1980 the Navy, at the request of the Japanese government, returned the orphaned Emily to Japan. It recently underwent a major restoration and is on display at the Museum of Maritime Science on Tokyo’s waterfront.

During the war the Kawanishi factory in Kobe, a coastal city about 20 miles southwest of Kyoto, built 167 Emily flying boats before the U.S. Army Air Forces added the factory to the strike list of B-29s raiding Japan. At one time, the factory was the largest enclosed structure in Asia. By war’s end, it was a twisted ruin. Today, as ShinMaywa workers climb over a US-1A brought in for overhaul, sunlight streams through bullet holes left in the factory walls.

For Kawanishi, the postwar years were difficult ones. While Japan was under U.S. occupation, the company was forbidden to build aircraft. Its workers transferred their skills in aluminum and metal working to making pots and pans, and later the company expanded into building and maintaining trucks. Before long, the massive hangars where the Emily had been assembled were rebuilt and filled with hundreds of trucks in various stages of construction or repair. Kawanishi changed its name to ShinMaywa to escape some of the notoriety that stemmed from its World War II operations.

At the outbreak of the Korean War, ShinMaywa was invited back into the aircraft business as a maintenance depot for U.S. military transports. The company had retained its expertise in flying boat construction and seized the opportunity to continue working with the technologies it had developed during World War II. Among its areas of interest was short-takeoff-and-landing (STOL) technology for marine aircraft.

With the help of the U.S. Navy, ShinMaywa acquired a Grumman UF-1 Albatross, an amphibious search-and-rescue aircraft with a 2,850-mile range that served not only the Navy but the U.S. Air Force and Coast Guard as well. The Albatross could accommodate a crew of six and was powered by two 1,425-horsepower Wright R-1820 engines. To create a STOL aircraft, ShinMaywa added two 600-hp Pratt & Whitney R-1340 engines, stretched the nose, and refitted the aircraft with a high T-tail. The modified Albatross was named the UF-XS and became a research platform for investigating STOL technologies.

The limiting factor in open-ocean operations is the impact stress created by waves slamming against the hull during takeoff and landing; reducing takeoff and landing speeds reduces the stress on the aircraft. ShinMaywa experimented with an array of high-lift devices to enable the UF-XS to take off and land at slower speeds. The tailplane and outer sections of the wings had leading edge slats. Flaps on the inner sections of the wings’ trailing edges could be deflected as much as 80 degrees, and on the outer sections, as much as 60 degrees. Engineers augmented these movable surfaces with an experimental system for controlling the boundary layer.

The boundary layer is a thin layer of air molecules near the surface of an aircraft (or any object moving through the air) that, because of the air’s viscosity, moves at a different velocity from the air farther from the surface. In fact there are a number of “layers” in the boundary layer, all flowing at slightly different velocities.

As an aircraft approaches the low speeds associated with landing, the boundary layer flowing over the wing becomes increasingly turbulent and the wing loses lift. To retain smooth flow, and therefore lift, as long as possible at slower speeds, ShinMaywa devised a system to blow air over the flaps and the elevator to keep the airflow smooth, enabling the aircraft to maintain lift and control at low speed. The air was produced by a 1,250-hp General Electric T58 turboshaft engine mounted in the aircraft cabin.

The UF-XS research showed that aircraft with such a system for boundary layer control (BLC)—as well as improved hull designs—could operate in much rougher seas than had been possible before. ShinMaywa incorporated the high-lift devices developed for the research program into the design of the anti-submarine PS-1 and the US-1/US-1A rescue aircraft.

The company built 23 PS-1 anti-submarine aircraft and 18 US-1/US-1A search-and-rescue aircraft. Although their BLC systems are unique, the amphibians inherited their configurations in part from their noted ancestor, the Kawanishi H8K-2 Emily. Their four General Electric T64 turboprop engines, license-built by Ishikawajima and each rated at 3,493-hp, are suspended from a wing set high on the fuselage. Seaplane designers place the engines as high off the water as possible to keep the air intakes from ingesting water. Also, saltwater is abrasive and corrodes propellers as well as the numerous rotating blades inside turbine engines. Besides mounting the engines high, ShinMaywa designers added a spray-suppressing chine around the forward hull.

All PS-1 and US-1 aircraft have been retired, but seven US-1As remain in service, and the type is still in production. As US-1A number 19 neared completion at the Kobe factory last year, the next generation of rescue amphibian was emerging right beside it.

The US-1A “Kai” is based on the 1960s technology of its predecessors and therefore has the same capabilities for STOL and rough-sea takeoffs and landings. But the Kai (Japanese for “modification”) also incorporates a pressurized hull that will allow the aircraft to fly at 30,000 feet instead of its current 10,000. At higher altitudes, the Kai will have greater range and will avoid the weather that limited US-1A operations. The Kai will also include modern satellite navigation and communication systems. The flight deck features a head-up display and night vision technology and resembles the glass cockpits of contemporary airliners. The first airframe was completed last month, and a rollout is scheduled for March 2003.

ShinMaywa managers believe the improvements will help the new amphibian compete for world sales, and they hope to market it not only as a search-and-rescue craft but also as an air tanker for fighting forest fires or a patrol aircraft for maritime research. “We think the Kai is the only aircraft capable of open ocean landing,” says ShinMaywa engineer Katsuhito Akashi. “There are other amphibious aircraft available, but none of them are capable of landing in those conditions.” Akashi points out that to investigate an ocean oil spill, a ship might need as much as a week to travel to the spill site and back. The Kai could make that round trip in a single day.

The Kai’s only competitors for such markets are amphibians produced by the Russian company Beriev, known for a long series of marine aircraft dating back to the 1930s (see “When Ships Have Wings,” Dec. 1995/Jan. 1996). Beriev, located in Taganrog near the border of Russia and Ukraine, received certification last year for its twin jet Be-200 and earlier this year for the smaller piston-engine Be-103. The company has built ten Be-103s, six of them for Russia’s forestry service.

The big Beriev, powered by two MotorSich D-436TP turbofan engines, each producing 1,650 pounds of thrust, can cruise at over 400 mph, but it is more expensive to operate than the Kai and can land only in seas with waves no higher than four feet. With the latter limitation, the Beriev is useful for lake and river landings but is not as capable as the Kai for ocean search and rescue. Beriev is marketing a transport version of the Be-200, which could seat as many as 70 passengers, and hopes to begin building as many as seven Be-200s each year.

If the Kai is to compete head to head with the Beriev, ShinMaywa will need export approval from the Japanese government. The Japanese constitution, written largely at the direction of the United States and its allies after World War II, prohibits any Japanese product capable of offensive military action from being sold to another country. Since the US-1 and US-1A began their lives as anti-submarine aircraft, ShinMaywa cannot sell them overseas.

The main differences between the Kai and the US-1A are the Kai’s fly-bywire controls and its pressurized hull, but these are significant enough, ShinMaywa managers hope, to earn a new designation that will enable the company to pursue overseas sales.

The Kai’s first stop, however, will be Japan Maritime Self Defense Force Base Iwakuni, on the southern tip of the big island, Honshu. The former headquarters of Admiral Isoroku Yamamoto and a former fighter base for the Japanese Imperial Navy, Iwakuni now hosts U.S. Marines flying F/A-18s. It is also home to Air Rescue Squadron 71, and when the first Kais complete flight testing, they will be based at Iwakuni with the seven US-1As that are still in service. It was a Squadron 71 crew that rescued Captain John Dolan in 1992.

Captain Dolan is now Major Dolan, an F-16 flight instructor in the Air Force Weapons School at Nellis Air Force Base in Nevada. Of his 1992 rescue, he says: “From ejection to rescue was a whole series of miracles.” No other aircraft in the world inventory could have gotten to him in time in the sea conditions he was experiencing. “Six hundred and eighty nautical miles from shore,” he remembers, “nine- to 12-foot seas, 25-knot surface winds, and I am here to tell the story!”

Flying boats and amphibians have all but disappeared, but, as Dolan will tell you, there’s at least one good reason to keep the old—and new—hull landers around.

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