Kawasaki OH-1

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]

 

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]

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]

 

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]

 

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]

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.

• 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]

  Japan

• Japan Ground Self-Defense Force^[21]

 

 

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]

External videos
Kawasaki OH-1 Public Flight Demonstration
OH-1 Performing Maneuvers and Landing

Aircraft of comparable role, configuration, and era

• Bell ARH-70 Arapaho
• Bell 360 Invictus
• Boeing–Sikorsky RAH-66 Comanche
• Eurocopter Tiger ARH
• Leonardo Helicopters AW249
• HAL Prachand
• Harbin Z-19
• TAI/AgustaWestland T129 ATAK

Related lists

• List of military aircraft of Japan
• List of rotorcraft

• 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.

 

Wikimedia Commons has media related to Kawasaki OH-1.

• Official JGSDF page
• Kawasaki Aerospace Division OH-1 page
• TS1engine | Mitsubishi Heavy Industries, Ltd.