The Shin Meiwa PS-1 and US-1A (Japanese: 新明和 PS-1, US-1A) are large STOL aircraft designed for anti-submarine warfare (ASW) and air-sea rescue (SAR) work respectively by Japanese aircraft manufacturer Shin Meiwa. The PS-1 was a flying boat which carried its own beaching gear on board, while the US-1A is a true amphibian. The aircraft has been replaced by the ShinMaywa US-2.
In 1962, Shin Meiwa flew a flying boat testbed, the UF-XS, converted from a Grumman HU-16 Albatross to build upon its wartime experience (as Kawanishi) and demonstrate its ideas on building flying boats that could land and take-off from the open ocean. It was fitted with a novel boundary layer control system to provide enhanced STOL performance, while the Albatross's two 1,425 hp (1,063 kW) Wright R-1820 radial engines were supplemented by two 600 hp (450 kW) Pratt & Whitney R-1340 radial engines on the aircraft's wings, with an additional 1,250 shp (930 kW) General Electric T58 turboshaft inside the aircraft's hull to drive the boundary layer control system. In 1966, the Japan Maritime Self-Defense Force (JMSDF) awarded the company a contract to further develop these ideas into an anti-submarine warfare (ASW) patrol aircraft. Two prototypes were built under the designation PS-X and flight tests began on October 5, 1967, leading to an order for production under the designation PS-1 in 1969.
The aircraft was able to land in seas up to 3 metres (9.8 ft) in height. Water distance for takeoff or landing with 79,400 pounds (36,000 kg) aircraft weight was 720 feet (220 m) with no wind or 500 feet (150 m) into a 15-knot wind. Apart from the boundary layer control system (powered by an independent gas turbine carried in the fuselage), the aircraft had a number of other innovative features, including a system to suppress spray during water handling, and directing the propwash from the aircraft's four turboprop engines over its wings to create yet more lift. Between 1971 and 1978, the JMSDF ordered 21 of these aircraft, and operated them as Fleet Air Wing 31 from 1973 until 1989 when they were phased out and replaced by Lockheed P-3 Orions. The small production run resulted in an extremely high unit-cost for these aircraft, and the programme was politically controversial.
The PS-1 ASW variant carried homing torpedoes, depth charges and 127mm Zuni rockets as offensive armament but had no defensive weapons. It was equipped with dipping sonar, which had limited use as it required the aircraft to land on water to deploy. It could also carry up to 20 sonobuoys. It had a crew of ten: pilot, co-pilot, flight engineer, navigator and six sensor/weapons operators.
The PS-1 had not been in service long before the JMSDF requested the development of a search-and-rescue variant. The deletion of the PS-1's military equipment allowed for greater fuel capacity, workable landing gear, and rescue equipment. The new variant, the US-1A, could also quickly be converted for troop-carrying duties. First flown on October 15, 1974, it was accepted into service the following year, and eventually 19 aircraft were purchased. From the seventh aircraft on, an uprated version of the original engine was used, but all aircraft were eventually modified to this US-1A standard. The US-1A's first rescue was from a Greek vessel in 1976. Between that time and 1999, US-1As had been used in over 500 rescues, saving 550 lives.
With the US-1A fleet beginning to show its age, the JMSDF attempted to obtain funding for a replacement in the 1990s, but could not obtain enough to develop an entirely new aircraft. Therefore, in 1995, ShinMaywa (as Shin Meiwa was by then renamed) began plans for an upgraded version of the US-1A, the US-1A kai (US-1A 改 - "improved US-1A"). This aircraft features numerous aerodynamic refinements, a pressurised hull, and more powerful Rolls-Royce AE 2100 engines. Flight tests began on December 18, 2003. The JMSDF purchased up to 14 of these aircraft, which entered service as the ShinMaywa US-2.
The US-1A was retired on December 13, 2017 when the last example in JMSDF service made its final flight. A total of 827 people have been recued by US-1s since the type entered service in 1976.
In 1977 Shin Meiwa had several ideas for its STOL flying boat concept on the drawing board but none were ever built. They were the Shin Meiwa LA (Light Amphibian), a 40-passenger light amphibian for inter-island feeder service; the 400-passenger Shin Meiwa MA (Medium Amphibian); the Shin Meiwa MS (Medium Seaplane) a 300-passenger long-range flying boat with its own beaching gear; and the gargantuan Shin Meiwa GS (Giant Seaplane) with a capacity of an astonishing 1200 passengers seated on three decks. Unlike the Shin Meiwa LA and MA which were like the US-1 in design, the Shin Meiwa MS and GS had their engines located in front of and above the wing to take advantage of the Coandă effect. In the end, none of the four designs got beyond the drawing boards.
Data from Jane's All The World's Aircraft 1988-89
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