The Shin Meiwa PS-1 / US-1 / US-2 & Harbin SH-5 Flying Boats

v2.0.1 / 01 jun 15 / greg goebel / public domain

* While the large flying boat is generally a thing of the past, there are a few survivors. Among them are the Japanese Shin Meiwa "PS-1" / "US-1" / "US-2", and the Chinese Harbin "SH-4". These big, elegant, four-turboprop aircraft remain in service in limited numbers. This document provides a history of the PS-1, US-1, and SH-5 -- as well as the smaller Canadair / Bombardier CL-215 / CL-415 flying boat.

Shin-Meiwa US-2 flying boat



* The Japanese Kawanishi aircraft company had designed a number of flying boats into World War II, most significantly the superlative H8K, one of the best flying boats of the conflict. While Japan's defense industries were suppressed by the American occupation authorities after the country's defeat, they slowly began to re-emerge as the US turned to Japan as an East Asian ally in the Cold War against the Communist Bloc. The Kawanishi company was resurrected in 1949 as "Shin Meiwa", in the relatively humble role of a service company that overhauled American, and later Japanese, military and civil aircraft.

However, the company had not forgotten its roots, and in 1959 Shin Meiwa rebuilt a Grumman UF-1 Albatross flying boat provided by the US Navy to experiment with new flying boat concepts. The modified Albatross, designated the "UX-FS", performed its initial flight on 25 December 1962. The UX-FS was fitted with four engines, two of them the Albatross's normal Wright R-1820 radials with 1,065 kW (1,425 HP) each, plus two additional Pratt & Whitney R-1340 radials with 450 kW (600 HP) each. The aircraft's hull was extensively modified, and the Albatross's conventional tail was replaced by a tee tail.

The UF-XS was also fitted with a General Electric (GE) T58 turboshaft engine providing 935 kW (1,250 SHP), mounted above and behind the cockpit. This engine simply blew air over the flaps and tail to provide a "boundary layer control (BLC)" system for improved short take-off & landing (STOL) performance. The UF-XS was flown in trials into 1964, and validated many concepts for advanced flying boat design.

* In January 1966, the Japanese Defense Agency (JDA) awarded Shin Meiwa a contract for further development of the company's flying boat concepts. The contract specified development of two full-scale prototypes, with the project designation "PX-S" and company designation "SS-2". The PX-S was intended primarily for antisubmarine warfare (ASW). Dr. Kikuhara Shizuo was in charge of the design team.

The first PX-S prototype took to the air from Kobe harbor on 5 October 1967, with the second following on 14 June 1968. Evaluation by the Japan Maritime Self-Defense Force (JMSDF) began late in 1968. The results of the evaluation were positive, and two preproduction "PS-1" aircraft were ordered in March 1969, with initial delivery in late 1971.

The PS-1 was powered by four General Electric T64-IHI-10 turboprop engines providing 2,280 kW (3,060 SHP) each, built under license by Ishikawajima-Harima Heavy Industries (IHI), mounted on a high-set wing. Each engine drove a three-blade reversible-pitch Hamilton Standard propeller. As with the UF-XS test aircraft, a GE T58 turboshaft engine, also built by IHI, was mounted in the upper center of the fuselage to drive a BLC system for improved STOL performance. In addition, the T58 could be used as an auxiliary power unit (APU). STOL capability was further enhanced by leading-edge slats on the outboard sections of the wings and the tailplane, as well as overwing spoilers and large flaps. Take-off speed was about 90 KPH (55 MPH).

The PS-1 featured a tall tee tail like that of the UF-XS. A fixed stabilizing float was fitted to each wingtip, and the aircraft had built-in retractable tricycle beaching gear, though it could only actually land on water. The nose gear retracted into the hull, while the main gear pivoted up into the sides of the fuselage.

The aircraft was fitted with an interesting system in which water was pumped alongside the fuselage to suppress sea spray; spray was also deflected by strakes mounted alongside the nose of the aircraft. These measures helped to ensure that the engines wouldn't be flooded with sea water on landings and takeoffs. A sea anchor was carried in the bow. The aircraft's boat hull was unusually slender, making it very stable in rough seas, and it could land and take off in swell heights of up to 4.3 meters (14 feet). Most flying boats can operate only on calm seas or protected waters, but the PS-1 was capable of landings and takeoffs under severe ocean conditions. The seaworthiness of the PS-1 was far superior to that of any World War II flying boat.

Sensor systems included search radar with the antenna in a prominent nose radome; a "magnetic anomaly detection (MAD)" system with a retractable tail "stinger; a "Jezebel" passive sonar system with 20 sonobuoys; a "Julie" active sonar system using explosive charges to generate sound pulses for the sonobuoys; and a searchlight mounted under the right wing. Four 150 kilogram (330 pound) depth charges could be carried internally. Pods between the engines on each wing could carry two homing torpedoes each, for a total of four torpedoes, while a pod on each wingtip could accommodate three 127 millimeter (5 inch) rockets, for a total of six rockets. There was no defensive armament.

The PS-1 carried a crew of nine, including pilot and copilot; flight engineer; radio operator; radar operator; MAD operator; two sonar operators; and a tactical coordinator. The raised flight deck provided excellent visibility, and bunks were included for long-range patrols. The end result was a very appealing aircraft, a worthy successor to the H8K of World War II.

* The JMSDF ordered a total of 21 PS-1s, not counting the two prototypes, with the last delivered in the spring of 1978. However, as often happens with Japanese defense programs, the protracted development and small production run of the PS-1 led to very high unit costs. The program was politically controversial, all the more so because PS-1s suffered a series of accidents -- though the mishaps were not related to design or construction faults. Another difficulty was that though the idea of using a flying boat for ASW operations had its attractions, in that the aircraft could set down on the water and drop a dunking sonar to hunt for submarines, in practice land-based aircraft could do a perfectly adequate job of ASW at much lower cost. Procurement of the PS-1 was halted in 1980 in favor of the Lockheed P-3C Orion, and the PS-1 was completely out of service by 1989.



* Retirement of the PS-1 did not take Japan completely out of the flying boat business. Early in PS-1 production, the JMSDF asked Shin Meiwa to develop an amphibian version of the PS-1 for the "search and rescue (SAR)" role to replace the service's Grumman UF-1 Albatross flying boats. The new SAR flying boat was given the military designation of "US-1" and the company designation of "SS-2A". Since the aircraft was effectively just a PS-1 with different kit, there was no US-1 prototype. Initial flight of the first US-1 was on 15 October 1974, with introduction to service in 1975.

The US-1 was much like the PS-1, but lacked armament and all sensor systems except ocean search radar. It had additional fuel capacity and was fitted with true landing gear to allow it to take off and land on airstrips. The main gear resembled that of the PS-1, but was scaled up, featuring two wheels on each gear assembly, and retracted into prominent fairings on the fuselage under the wings. The track was narrow, but the aircraft still handled well on crosswind landings.

Shin-Meiwa US-1 flying boat

Additional "bubble" windows were provided for observers, and along with rescue hatches with folding ramps, a large sliding door was built into the right side of the aircraft to allow launch and recovery of an inflatable rescue dinghy. A hoist was fitted above the sliding door; a loudspeaker system allowed the flight crew to give instructions to survivors; and a dye-marker launcher, with a capacity of ten markers, could be used to mark patches of sea during rescue operations.

The US-1 had a crew of eight, including pilot; copilot; flight engineer; navigator; radio operator; radar operator; and two observers. Up to five medics or rescue divers could be carried as well. The aircraft could accommodate 12 stretchers and three sitting passengers, or 36 sitting passengers. In principle, the SAR gear could also be removed to allow conversion of the US-1 into a troop transport with seating for 100.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                33.15 meters        108 feet 9 inches
   wing area               135.82 sq_meters    1,462 sq_feet
   length                  33.46 meters        109 feet 9 inches
   height                  9.82 meters         32 feet 3 inches

   empty weight            25,500 kilograms    56,220 pounds
   loaded weight           45,000 kilograms    99,200 pounds

   max speed at altitude   495 KPH             310 MPH / 270 KT
   service ceiling         8,200 meters        27,000 feet
   range                   4,200 kilometers    2,610 MI / 2,270 NMI
   _____________________   _________________   _______________________

An initial batch of 12 US-1s was built. The seventh and following aircraft were fitted with uprated T64-IHI-10J turboshaft engines providing 2,605 kW (3,490 SHP) each; these aircraft were designated "US-1A", with earlier production aircraft upgraded to the same standard. A total of 20 US-1 / US-1A machines was manufactured up to the last example, built in 2004. The US-1 has proven extremely useful and capable, and was heavily employed in maritime SAR activities after the shoot-down of Korean Air Lines flight 007 by the Soviets in 1983. Up to 1999, the US-1 / US-1A was credited with saving 550 lives.

Shin Meiwa proposed a commercial transport version of the US-1 with seating for 69 passengers, but it was just too expensive and didn't happen. The first prototype of the PS-1 and a US-1 were also used in trials by the JMSDF and Japan National Fire Agency as a "water bomber" to fight forest fires.

* Despite the small production numbers of the PS-1 and US-1, production of the family is continuing with a new version, originally designated the "US-1A Kai", where "Kai" is short for "kaizen (modification)". The project was initiated in 1996, with the development contract specifying construction of two flight prototypes and two static-test prototypes. The first prototype performed its initial flight on 18 December 2003, taking off and landing in Osaka Bay.

The US-1A Kai was externally very similar to the US-1A, the most significant difference being that it was fitted with substantially more powerful Rolls-Royce AE-2100J engines, providing 3,425 kW (4,590 SHP) each, driving Dowty six-bladed propellers instead of the three-bladed propellers of the US-1A. The flap-blowing system was driven by an LHTEC CTS800-4K turboshaft, a civil version of the T800 military turboshaft, providing max power of about 1,015 kW (1,360 SHP). Performance and takeoff weight were improved.

The US-1A Kai also had a modified wing with integral fuel tanks and a pressurized upper cabin, permitting a ceiling of 6,100 meters (20,000 feet), twice that of the unpressurized US-1A. Avionics were updated, including a glass cockpit and French Thales Ocean Master search radar. No doubt the modernized avionics suite included a Global Positioning System navigation satellite receiver, a very handy item for an oceanic SAR machine. The first production machine went into formal JMSDF service in 2007, with the aircraft receiving the service designation of "US-2". It is unclear if IHI is license-building the AE-2100J engines.

Shin-Meiwa US-2 flying boat

It was initially believed that all seven surviving US-1As would be upgraded to US-2 standard and that three production US-2 machines would be built, but considering how previous purchases in the series have been strung out from year to year, an estimate of how many US-2 machines will be built would probably not be very meaningful. The Japanese government considered buying a foreign machine, most likely a modern Russian Beriev flying boat, but decided -- probably for political reasons, though it is plausible that no other machine really fit JMSDF needs -- to buy from a domestic manufacturer, even though with such low production rates a foreign machine would be much cheaper. Whatever the case, in the 21st century the big Shin Meiwa machine remains a lovely testament to the romance of the flying boat.



* While the Japanese were developing the PS-1, the Chinese began work on a comparable aircraft. In early 1970, after several years of consideration of various preliminary designs, the Harbin Aircraft Manufacturing Corporation (HAMC) and the Chinese Seaplane Design Institute began formal work on a four-turboprop flying boat that could be used for maritime warfare, SAR, and cargo transport roles. The aircraft was to be designated the "Maritime Bomber 5 (Shuishang Hongzhaji 5 / SH-5)", though sources mention an alternate "PS-5" designation.

A static test airframe was completed in 1971, but due to the upheavals and lunacy of the Chinese "Cultural Revolution", tests did not begin until August 1974. A flying prototype had been rolled out in December 1973, with the machine beginning taxi trials in May 1975 and performing its first flight on 3 April 1976. The slow pace of the program continued, a single production batch of six aircraft being completed in 1984 and 1985, with four of them handed over to the People's Liberation Army Naval Air Force in 1986. They have been retained in service, and may have received some combat electronic system updates.

Harbin SH-5 flying boat

* The SH-5 has a very general resemblance to the PS-1 / US-1, with a long, relatively slender, fuselage and hull, a high wing with four turboprops, and a fixed float near each wingtip. However, when inspected in more detail it clearly more resembles the Soviet Beriev Be-12 flying boat, with a twin-fin tail and very similar nose layout.

The SH-5 is powered by four Dongan WJ5A turboprop engines with 2,350 kW (3,150 SHP) each, driving four-bladed propellers. The aircraft is a pure seaplane, though it does have built-in beaching gear roughly similar to that of the PS-1. There are spray-suppression strakes on each side of the nose, and a small sea rudder at the rear of the hull.

The SH-5 is armed with a dorsal turret mounting twin cannon, and there are two stores pylons on each wing, one placed between the hull and the inboard engine, the second placed between the inboard and outboard engines. These four stores pylons can each be fitted with an antishipping missile, or each of the outer stores pylons can be fitted with three homing torpedoes. Six tonnes (13,200 pounds) of other stores, such as depth charges, mines, bombs, sonobuoys, or rescue gear can be stored in a rear compartment in the fuselage. A Doppler search radar is fitted in a thimble radome in the nose, and a fixed MAD boom is fitted to the tail. If configured as a cargolifter, the SH-5 can carry 10 tonnes (22,000 pounds) of cargo.

Harbin SH-5 flying boat

The SH-5 carries a flight crew of eight, including a pilot; co-pilot; navigator; flight engineer; radio operator; and three systems specialists. The number of specialists may vary depending on the mission. The fuselage is unpressurized. There are three freight compartments behind the cockpit area, followed by a cabin for the mission crew, a compartment for communications gear, and finally the stores compartment. There is a corridor connecting all three compartments, with watertight doors between compartments. There is one crew door on the left side of the aircraft and two doors on the right.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                36 meters           118 feet 1 inch
   wing area               144.0 sq_meters     1,550.05 sq_feet
   length                  38.9 meters         127 feet 8 inches
   height                  9.8 meters          32 feet 2 inches

   empty weight            26,500 kilograms    58,400 pounds
   max loaded weight       45,000 kilograms    99,200 pounds

   max speed at altitude   555 KPH             345 MPH / 300 KT
   service ceiling         10,250 meters       33,650 feet
   range                   4,750 kilometers    2,950 MI / 2,565 NMI
   _____________________   _________________   _______________________

One of the aircraft not delivered to the Navy was apparently evaluated as a "water bomber" for fighting forest fires. It seemed that the SH-5 was a dead-end type for years, but in 2009 the Chinese Avic aviation manufacturing group announced plans for a derivative, the "AG600 (previously TA-600) Jiaolong" amphibian, named after a type of Chinese sea dragon.

Digital models show an aircraft that looks much like the SH-5, but lacks the nose glazing and MAD boom, has a smaller nose radome, and a single tailfin in a tee tail arrangement. It will have about a 10% greater MTO weight. It is intended for fire-fighting and SAR, with first flight in 2016 and introduction to service currently scheduled for 2017.



* In the early 1960s, the Canadair company of Canada began studies for a flying boat, ultimately converging on a twin-engine amphibious aircraft, primarily intended for fire-fighting. Initial flight of the prototype "CL-215" was on 23 October 1967, with initial customer deliveries in 1969.

The CL-215 was a straightforward aircraft of deliberate simplicity, featuring all-metal construction with protection against salt water, a boxy flying boat fuselage, a straight high-mounted wing, a swept tailfin, and a straight tailplane mid-mounted on the tailfin. There was a water deflection strake wrapped around the nose. The CL-215 was powered by twin Pratt & Whitney R-2800 Double Wasp air-cooled two-row 18-cylinder radial engines, providing 1,565 kW (2,100 HP) each and driving three-bladed Hamilton Standard propellers. Fuel was carried in wing cells.

The retractable landing gear featured twin-wheel nose gear and single-wheel main gear, the main gear tucking up to the sides of the fuselage, but not actually retracting inside. There was a fixed float near each wingtip. Flight control arrangement was conventional: one-piece slotted flaps, ailerons, rudder, elevators, and trim tabs. Flight controls were manual, except for hydraulically-boosted flaps. Avionics were conventional as well: radios plus navigation and landing aids. There were dual controls and two aircrew. There were doors fore and aft of the wing on the left, an emergency exit door behind the wing on the right, an escape hatch above the cockpit, and a mooring hatch on top of the nose.

Canadair CL-215

The baseline CL-215 was configured for both fire-fighting and utility duties. It featured twin tanks for water or fire retardant, with scoops on the bottom for picking up water from lakes or rivers, and drop doors for dispensing the load. A sprayer kit was offered to allow the CL-215 to spray pesticides and the like. Along with the tanks, there were folding seats for 8 passengers; removing part or all of the tank kit allowed carriage of up to 36 passengers. There was also a SAR version, with a nose thimble for AN/AVQ-21 radar, optional searchlight, IFF and better navaids, plus bulged windows. The SAR version's crew added a navigator, flight engineer, and two observers, along with provisions for four seats or six stretchers.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                28.6 meters         93 feet 10 inches
   wing area               100.3 sq_meters     1,080 sq_feet
   length                  19.82 meters        65 feet 
   height                  8.92 meters         29 feet 3 inches

   empty weight            12,160 kilograms    26,810 pounds
   max takeoff weight*     17,100 kilograms    37,700 pounds

   cruise speed            290 KPH             180 MPH / 155 KT
   service ceiling         10,250 meters       33,650 feet
   range                   2,090 kilometers    1,300 MI / 1,130 NMI
   _____________________   _________________   _______________________
   * takeoff from water, MTO for land takeoff was 15% greater

Total build of the CL-215 up to end of production in 1990 was 125 aircraft. The most prominent users were Canada -- provincial governments and some commercial users -- the French Securite Civile, and Greece; other users included Italy, Portugal, Spain, Thailand, Turkey, Venezuela, and Yugoslavia. The CL-215 became a common sight in European wildfire-fighting operations.

* In the late 1980s, Bombardier -- which had taken over Canadair -- began to investigate turboprop power for the CL-215, initially focusing on an update program for existing CL-215 flying boats. From 1987, two CL-215s were kitted up with Pratt & Whitney Canada (PWC) PW123AF turboprops with 1,775 kW (2,380 SHP) each, driving four-bladed reversible Hamilton Standard propellers, performing test flights from 1989. The "CL-215T" upgrade was offered from 1990 and proved popular. New-production machines, designated "CL-415", were offered from 1994.

Canadair CL-415

The CL-415 retained the CL-215 airframe, but along with the PWC turboprops featured airframe improvements; powered flight controls and a proper glass cockpit; wingtip endplates / winglets to improve stability and allow use of full engine power; "finlets" on the tailplane, plus a bullet fairing at the tailfin-tailplane junction; a larger four-tank water / retardant system; and a stores pylon under each wing. The SAR version was designated "CL-415M".

It is unclear if the CL-215T upgrade brought a CL-215 up to full CL-415 spec. Bombardier continues to build the CL-415, with CL-215 users often buying them up. Although the CL-215 / 415 is a much less impressive flying boat than the PS-1 / US-1 or SH-5, the number of CL-215 / 415 machines built shows it to have been much more successful than both of its larger contemporaries put together.



* Incidentally, the Shin Meiwa firm has recently taken to transcribing its name in English as "ShinMaywa", presumably to make it easier for foreigners to correctly pronounce. For the moment, it's hard to see it makes much difference, the name being spelled in Kanji in Japanese anyway.

* Sources include:

* Revision history:

   v1.0   / 01 may 01 / Originally discussed PS-1 / US-1 only.
   v1.1.0 / 01 jan 02 / Added comments on Chinese SH-5.
   v1.1.1 / 01 apr 02 / Minor typo fixes.
   v1.1.2 / 01 apr 04 / Added US-1A Kai material, small fixes.
   v1.1.3 / 01 apr 06 / Review & polish.
   v1.1.4 / 01 feb 08 / Review & polish.
   v1.1.5 / 01 mar 09 / Jiaolong comments.
   v1.1.6 / 01 oct 11 / Review & polish.
   v2.0.0 / 01 jul 13 / Added CL-215 & CL-415, added "US-2" designation.
   v2.0.1 / 01 jun 15 / Jiaolong updates.