Engineering:Kawasaki OH-1

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Short description: Japanese scout/observation helicopter
OH-1
ＯＨ－１ (4).jpg
A Kawasaki OH-1 in flight
Role Scout/observation helicopter
National origin Japan
Manufacturer Kawasaki Aerospace Company
First flight 6 August 1996
Introduction 2000
Status In service
Primary user Japan Ground Self-Defense Force
Produced 1996–2013
Number built 38 as of 2013[1]

The Kawasaki OH-1 (nickname: "Ninja") is a military scout/observation helicopter developed and manufactured by the Kawasaki Aerospace Company. The primary operator is the Japan Ground Self-Defense Force (JGSDF), who originally procured the OH-1 as a domestically produced successor to their existing OH-6D Loach fleet. The OH-1 has the distinction of being the first helicopter to be entirely produced in Japan.[2]

In addition to its use as an observation helicopter, it can also be armed to directly participate in combat; such weapons include a limited quantity of air-to-air missiles for self-defense purposes. Several variants of the OH-1 have been proposed, these have included derivatives of the type to serve as an attack helicopter as well as an aborted project to develop a utility helicopter. As of March 2014, a total of 38 OH-1s have entered service with the JGSDF; so far these complement the existing OH-6Ds rather than replace them.[3]

In December 2022, the Japanese government decided to replace 33 OH -1, 12 AH-64D, 47 AH-1S, and 26 U-125A with unmanned aerial vehicles. Japan plans to increase its defense budget from 1.24% of GDP in fiscal 2021 to around 2.0% within 10 years, and has decided to retire these helicopters and aircraft as part of an effort to spend its defense budget efficiently.[4]

Development

Origins

During the late 1980s, the JGSDF developed a requirement for a new scout/observation helicopter to replace its Kawasaki license-built OH-6Ds, which became the OH-X programme.[5] In June 1989, the JGSDF announced their intention to pursue the development of the OH-X.[1] Several proposals to meet the OH-X requirement were submitted by Kawasaki, Fuji and Mitsubishi. In 1991, Kawasaki's proposal was selected by the JGSDF's Technical Research and Development Institute as the prime contractor for the OH-X programme.[1] On 18 September 1992, the Kawasaki design formally appointed by the Ministry of Defense as the winner.[2][5] Kawasaki was made responsible for producing 50 percent of the airframe, as well as coordinating development of the rotor system; the remaining airframe elements were manufactured by Mitsubishi and Fuji.[1] Development was formally launched in October 1992.[1]

A JGSDF OH-1, 2012

In early 1996, the first OH-1 prototype was rolled out.[1] On 6 August 1996, the first of four OH-1 prototypes (designated XOH-1) performed the type's maiden flight. All four prototypes were flying by March 1997.[1] The four prototypes were delivered to the Japanese Defence Agency for service testing from June to August 1997.[6] By April 1998, flight testing of the prototypes was reportedly around half way complete, having accumulated a combined 400 flight hours during testing, further tests focused on flight validation, operational evaluation, and mission equipment functionality.[7] These four prototype aircraft were all later remanufactured to conform to production standards and redelivered under new serial numbers to the JGSDF.[1]

In June 1998, in response to the finalising of a production contract and an initial order for two OH-1s having been placed earlier that year, the manufacture of production OH-1s formally commenced;[6][7] By the late 1990s, the JGSDF had announced that it had planned to procure between 150[5] and 250 OH-Xs to meet its requirements.[1][6] This figure was significantly fewer than the 297 OH-6Ds that were in active service by March 1995, and there were repeated concerns that numbers could be further curtailed as a result of the impact of defense budget cuts. Procurement, and thus production, of the OH-1 was of a slow pace; each year, only a handful of rotorcraft would normally be purchased, such as a pair of OH-1s being the only units procured in 2004.[8][9] By 2013, production of the OH-1 was reportedly as presumed to have been terminated.[1]

Further development

During the 1990s, the JGSDF was interested in procuring a new attack helicopter during the following decade, seeking to replace the Fuji-built Bell AH-1 Cobra fleet. Amongst the proposals produced by Japanese industries was a derivative of the OH-1, tentatively designated as the AH-2.[10][11] In 1999, it was revealed that the JGSDF was actively studying the modification of the OH-1 into an attack helicopter suitable to their requirements.[12][13] The OH-1 had been intentionally designed with additional margin to accommodate such growth of scope, the main limiting factors being its transmission and engines. The AH-2 proposal would have involved installing uprated engines and the addition of new unspecified armaments for anti-tank combat missions; Boeing in particular was dismissive of the value of the proposed rotorcraft, claiming that it "cannot fulfill the attack requirement".[14] Kawasaki's proposal was ultimately rejected in favour of a locally-built variant of the Boeing AH-64 Apache.[1]

A pair of OH-1s in formation flight

In 2005, Kawasaki proposed the development of a utility-orientated derivative of the OH-1 in response to the fledgling UH-X programme, which intended to replace the JGSDF's outdated fleet of Fuji-built Bell UH-1J Iroquois helicopters.[15] This variant, which would have used the OH-1 as a base, would have featured a new cabin, avionics, transmission and engines, but would have also retained a high level of commonality between the observation and utility models. In 2006, the Japanese government approved a request to fund development of a more powerful variant of the OH-1's Mitsubishi TS1-10 engine.[16] In March 2007, Kawasaki was reportedly close to finalizing its plans for the utility-orientated OH-1 derivative of the OH-1.[17] In 2012, a refreshed proposal for the UH-X requirement was made by Kawasaki, emphasizing its use of OH-1 technology.[18] In July 2015, the Japanese Ministry of Defense (MoD) announced its decision to accept a rival bid made by Fuji/Bell to domestically produce a modified version of the Bell 412 to meet the UH-X requirement instead.[19]

In early 2007, Kawasaki confirmed that it was studying several capability improvements for the OH-1 in terms of adaptability, maneuverability and stability; industry sources also claimed that improvements to the range of the OH-1 along with significant power output increases from the type's TS-1-10 engines.[17] Alternative powerplants for the OH-1 have also been suggested, such as the LHTEC T800 and the MTR MTR390.[7] In late 2008, Kawasaki was considered implementing a series of improvements aimed at increasing the payload of OH-1; this proposed modification was dependent upon demand from the Japanese defense ministry.[20]

Design

The electro-optical sensor on upper fuselage of an OH-1

The OH-1 Light Observation Helicopter is a tandem-seat, twin-engine scout helicopter. It has a narrow fuselage fitted with small stub wings and a non-retractable tail wheel undercarriage. The OH-1 is suited to armed scout, light escort, and observation duties.[1] It is equipped with an automatic pilot system with flight holding functionality, while the cockpit features a multi-display system to lower workloads on its two-man crew.[2]

The OH-1 is powered by a pair of Mitsubishi TS1 turboshaft engines, equipped with Full Authority Digital Engine Controls (FADEC), which drives a four-blade composite main rotor with a bearingless rotor hub along with a Fenestron-type anti-torque tail rotor (an enclosed tail-fan unit). The Fenestron uses eight asymmetrically spaced blades to reduce both noise and vibration.[1][5]

A roof-mounted electro-optical sensor turret is located forward of the rotor head, containing a forward looking infrared sensor, a laser rangefinder and a colour TV camera. A total of four hardpoints are fitted under the rotorcraft's stub wings to allow the carriage of external stores, these have a total capacity of 132 kg (291 lb). The outer pylons can carry four Type 91 guided surface-to-air missiles, while the inner pylons are capable of carrying external fuel tanks for additional range or endurance.[5] No additional armament is typically fitted.[5]

Operational history

In January 2000, the first production standard OH-1 was delivered to the JGSDF.[1] The OH-1 is slated to replace the Hughes OH-6D, which remains in service as the primary aircraft in this role.

Variants

  • XOH-1: Prototype version
  • OH-1: Production model, used as an observation helicopter
  • AH-2: Proposed attack helicopter derivative that would have featured uprated engines and additional anti-tank armaments; rejected in favour of Boeing AH-64 Apache.[1]

Operators

 Japan
  • Japan Ground Self-Defense Force[21]

Specifications (OH-1)

Cockpit of an OH-1
Fenestron tail rotor, note the asymmetrical blades

Data from Kawasaki Aerospace[2]

General characteristics

  • Crew: 2 (pilot and observer)
  • Length: 12 m (39 ft 4 in)
  • Height: 3.8 m (12 ft 6 in)
  • Empty weight: 2,450 kg (5,401 lb)
  • Max takeoff weight: 4,000 kg (8,818 lb)
  • Powerplant: 2 × Mitsubishi TS1-M-10 [ja] turboshaft engines, 660 kW (890 hp) each
  • Main rotor diameter: 11.6 m (38 ft 1 in)
  • Main rotor area: 105.7 m2 (1,138 sq ft)

Performance

  • Maximum speed: 278 km/h (173 mph, 150 kn)
  • Cruise speed: 220 km/h (140 mph, 120 kn)
  • Range: 550 km (340 mi, 300 nmi)
  • Ferry range: 720 km (450 mi, 390 nmi)
  • Service ceiling: 4,880 m (16,010 ft)

Armament

  • Hardpoints: 4 × hardpoints under stub wings for auxiliary fuel tanks (inner hardpoints) and Type 91 air-to-air missiles (outer hardpoints)[22]

See also

Aircraft of comparable role, configuration and era

Related lists

References

Citations

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 "Forecast International: Intelligence Center". https://www.forecastinternational.com/archive/disp_pdf.cfm?DACH_RECNO=1007. 
  2. ↑ 2.0 2.1 2.2 2.3 "OH-1 Light Observation Helicopter." Kawasaki, Retrieved: 26 June 2016.
  3. ↑ "第II部 わが国の防衛政策の基本と防衛力整備" (in ja). Japanese Ministry of Defense. http://www.clearing.mod.go.jp/hakusho_data/2009/2009/html/ls229000.html. 
  4. ↑ 空自捜索機や陸自戦闘ヘリを廃止、無人機で代替へ…防衛予算効率化 Yomiuri Shimbun. 9 December 2022.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 Aoki 1999, pp. 37–44.
  6. ↑ 6.0 6.1 6.2 Taylor 1999, p. 305.
  7. ↑ 7.0 7.1 7.2 Lewis, Paul. "First OH-1 scout helicopters poised for series production." Flight International, 29 April 1998.
  8. ↑ Sobie, Brendan. "Defence cuts force Japan to slow helicopter output". Flight International, 13–19 January 2004. p. 18.
  9. ↑ "Reality check." Flight International, 28 September 2004.
  10. ↑ Lewis, Paul. "Japan eyes attack helicopter." Flight International, 31 July 1996.
  11. ↑ "Japan ready to flight test attack helicopter." Flight International, 7 October 1998.
  12. ↑ Jeziorski, Andrzej. "Japan's anti-tank OH-1 study heralds further delay to AH-X." Flight International, 4 August 1999.
  13. ↑ "AH-X bidders await end-of-year request." Flight International, 28 March 2000.
  14. ↑ "Japan rethinks helicopter needs." Flight International, 16 March 2004.
  15. ↑ "KHI prepares bid for UH-X." Flight International, 14 June 2005.
  16. ↑ "Kawasaki to develop new version of OH-1 helicopter." Flight International, 11 April 2006.
  17. ↑ 17.0 17.1 "Kawasaki to upgrade OH-1 for utility role." Flight International, 13 March 2007.
  18. ↑ Osborne, Tony. "Kawasaki to leverage OH-1 technology in new utility helicopter." Shepard Media, 29 May 2012.
  19. ↑ Grevatt, Jon. "Japan selects Fuji/Bell option for UH-X programme." IHS Jane's Defence Industry, 19 July 2015.
  20. ↑ Govindasamy, Siva. "Kawasaki talks civil." Flight International, 23 September 2008.
  21. ↑ "World Air Forces 2014". Flightglobal Insight. 2014. 
  22. ↑ Jackson 2007, pp. 395–396

Bibliography

  • Aoki, Yoshimoto. "Kawasaki OH-1". World Air Power Journal. Volume 38, Autumn/Fall 1999. London:Aerospace Publishing. ISBN:1-86184-035-7. ISSN 0959-7050. pp. 36–45.
  • Jackson, Paul (ed.) Jane's All the World's Aircraft 2007–2008. Coulsdon, UK: Jane's Information Group, 2007. ISBN:978-0-7106-2792-6.
  • Taylor, Michael J.H. Brassey's World Aircraft & Systems Directory 1999/2000. London:Brassey's, 1999. ISBN:1-85753-245-7.

External links



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