The Boeing/Sikorsky RAH-66 Comanche was an advanced five-blade armed reconnaissance and attack helicopter designed for the United States Army. Before mass production begun the RAH-66 program was canceled in 2004 after nearly $7 billion was spent on the program.
During the early 1980s, the U.S. Army began formulating a requirement for a replacement of its helicopters then in service, resulting in the Light Helicopter Experimental program. In 1991, the Boeing-Sikorsky team was chosen to produce prototypes. The Comanche would incorporate stealth technologies, featuring a number of designs previously untried. It was to employ advanced sensors in its reconnaissance role, and was intended to designate targets for the AH-64 Apache. The aircraft was also armed with missiles and rockets to destroy armored vehicles. Two RAH-66 prototypes were built and conducted flight testing from 1996 to 2004; since the cancellation the prototypes have been placed on display.
RAH-66A Comanche Specifications
General characteristics
- Crew: 2
- Length: 46.85 ft (14.28 m)
- Rotor diameter: 39.04 ft (11.90 m)
- Height: 11.06 ft (3.37 m)
- Disc area: 1,197 ft² (111 m²)
- Empty weight: 9,300 lb (4,218 kg)
- Loaded weight: 12,349 lb (5,601 kg)
- Useful load: 5,062 lb (2,296 kg)
- Max takeoff weight: 17,408 lb (7,896 kg)
- Powerplant: 2 × LHTEC T800-LHT-801 turboshaft, 1,563 hp (1,165 kW) each
- Fuselage length: 43.31 ft (13.20 m)
- Rotor systems: 5 blades on main rotor
Performance
- Maximum speed: 175 knots (201 mph, 324 km/h)
- Cruise speed: 165 knots (190 mph, 306 km/h)
- Range: 262 nmi (302 mi, 485 km) on internal fuel
- Combat radius: 150 nmi (173 mi, 278 km) on internal fuel
- Ferry range: 1,200 nmi (1,380 mi, 2,220 km)
- Endurance: 2.5 hr
- Service ceiling: 14,980 ft (4,566 m)
- Rate of climb: 895 ft/min (4.55 m/s)
Armament
- 1× 20 mm XM301 three-barrel cannon mounted in a Turreted Gun System (500 round capacity)
- Internal bays: 6× AGM-114 Hellfire air-to-ground missiles, or 6× AIM-92 Stinger air-to-air missiles, or 24× Hydra 70 2.75 in (70 mm) air-to-ground rockets
- Optional stub wings: 8× Hellfires, 16× Stingers, or 56× Hydra 70 rockets
Origins and LHX
In 1982 the U.S. Army started the Light Helicopter Experimental (LHX) program to replace UH-1, AH-1, OH-6, and OH-58 helicopters. It took six years, until 1988, before the request for proposal (RFP) was issued, in which requirement was changed to a reconnaissance helicopter. In October that year, the Boeing-Sikorsky and Bell-McDonnell Douglas teams received contracts for their designs. The program's name was changed to Light Helicopter (LH) in 1990. In April 1991, the Boeing-Sikorsky team was selected as the contest winner and received a contract to build four prototypes for a demonstration and evaluation (Dem/Val) phase. Also that month the helicopter was designated RAH-66 Comanche by the Army.
In November 1993, the first prototype began assembly at Sikorsky's Stratford and Boeing's Philadelphia plants, before the sub-assemblies were transferred to the former location for final assembly. The following year the number of prototypes was cut to two. The first Comanche prototype was rolled out of the Sikorsky Aircraft's helicopter production facility on 25 May 1995, before being transferred to West Palm Beach, Florida, for flight testing. The prototype, piloted by Bob Gradle and Rus Stiles, made its 39-minute maiden flight on 4 January 1996. The flight was originally planned for August 1995, but was delayed by structural and software problems. The second prototype made its first flight on 30 March 1999.
Design aspects
The RAH-66 was intended to be a stealth helicopter; incorporating a number of techniques were used to reduce radar cross-section (RCS) and other areas of viability. Radar-absorbent material (RAM) was used on the Comanche, as well as having infrared-suppressant paint applied on its faceted surface; with these measures, the Comanche's RCS is 360 times smaller than the AH-64 Apache attack helicopter. The Comanche's noise signature is noticeably quieter than comparitive aircraft; this was partly achieved through the all-composite 5-blade main rotor and tail rotor assembly.
The Comanche was equipped with sophisticated navigation and detection systems intended to allow operations at night and in bad weather. Each of the two crew-members had two LCD multi-functional displays in addition to the Helmet-Integrated Display and Sight System (HIDSS). It has a digital fly-by-wire system. Its primary mission was to use its advanced sensors to find and designate targets for attack helicopters, such as the AH-64. The RAH-66 also had its own light armament, it could carry six AGM-114 Hellfire and twelve FIM-92 Stinger missiles, split evenly between the two retractable weapons pylons. The Comanche was to be also fitted with the three-barrel XM301 20 mm cannon under its nose. More armament can be accommodated externally but would reduce the effectiveness of the stealth technologies.
The RAH-66 is powered by two LHTEC T800 turboshaft engines. Its fuselage is 43 feet (13 m) long and made of composite material. The F-22 Raptor-derived airframe was designed to fit more easily onto transport ships, enabling it to be deployed to hot spots quickly. If transport assets were not available, the Comanche's ferry range of 1,260 nmi (2,330 km) would allow it to fly to battlefields overseas on its own. The Comanche was specifically tailored to the role of armed scout, replacing the U.S. Army's current armed scout helicopter, the OH-58D Kiowa Warrior, which is an upgraded version of a Vietnam War-era observation helicopter. The Comanche is smaller and lighter than the AH-64.
Prototype testing
Flight testing was conducted with the two prototypes. After meeting key criteria, the RAH-66 entered the $3.1 billion engineering and manufacturing development (EMD) phase on 1 June 2000. An effort to reduce the Comanche's empty weight by approximately 200 lb (90.7 kg) or 2.1% to meet target weight was started later in 2000. Through the early 2000s, the U.S. Army planned to purchase over 1,200 Comanches to fill the scout and light attack roles, with deliveries of operational RAH-66s scheduled to begin in 2006. The first Comanche prototype, serial 94-0327, completed 318 flights over 387 hours before ending its testing career in January 2002. The second prototype, serial number 95-0001, had accumulated 93 flight hours and 103.5 sorties by May 2001.
The second RAH-66 received mission equipment and more powerful T800-LHT-801 engines and it continued flight testing from 23 May 2002, including testing of night vision and weapon systems, until 2003. During testing, the Comanche cruised at 162 knots (186 mph; 300 km/h), a "dash speed" of 172 knots (198 mph; 319 km/h), as well as demonstrating an ability to make a 180° turn in under 5 seconds.
In 2002 the program was restructured and the number of Comanches to be purchased was cut to 650. Production of this fleet had a projected total cost of $26.9 billion. The EMD phase was planned to last six years with five Comanches built for testing. Production on the third RAH-66, the first EMD helicopter, began in 2003. Subsequently eight RAH-66s were to be built for operational testing. The initial production RAH-66s were to be completed to a Block I configuration with most of the planned weapons and sensors. The 16th and later helicopters would be to the Block II standard and have all the planned capabilities.
Cancellation
On 23 February 2004, the U.S. Army announced their decision to cancel the RAH-66 Comanche program. The Army determined upgrades would be required for the RAH-66 to survive current anti-aircraft threats and decided to put the funding toward renovating its existing helicopter fleet of attack, utility, and reconnaissance aircraft. The Army also planned to use the program's funds to speed up development of unmanned aerial vehicles (UAVs). The Comanche program had spent US$6.9 billion at the time of its termination. Contract termination fees were estimated to total US$450–680 million for the main program partners Sikorsky and Boeing. The Army subsequently pursued the Bell ARH-70 to replace the OH-58D, but the ARH-70 was also canceled in October 2008, due to cost overruns.
Many reasons led to the ultimate cancellation of the RAH-66 program; according to author James Williams, efforts to speed up the program by cutting risk-mitigating measures and continuous adjustments for yearly budget cuts formed a deadly cycle that would greatly extend development schedules. Over the course of the Comanche's development, multiple government agencies would cut the number of helicopters to be ordered, especially on the basis that the Cold War had ended (the Peace Dividend), and this caused unit cost projections to rapidly climb, while led to the program encountering critics such as the Army Acquisition Executive James Ambrose, who had declared that the Army would not have an aircraft "costing a dollar over $7.5 million". By only 1995, the Comanche was facing complete cancellation as a choice between which defense development programs were to be scrapped. In mid-1999 the Comanche came under governmental scrutiny, the Government Accountability Office (GAO) reported "serious doubts" about the program and noted that it would "consume almost two thirds of the whole Aviation budget by Fiscale Year 2008". Army experiences from the Kosovo war had led to senior figures placing greater emphasis on unmanned platforms to conduct many of the same roles the Comanche was being developed to do. By 2000, Williams postulates that the main reason for keeping the program was out of concern for the state of the helicopter industry, Sikorsky's production and employment figures were at their lowest for decades and the contract was considered critical.
Author Fred Brooks criticized the need for the Comanche to ferry itself across the Atlantic as an example of excess requirements in a project's design phase and their repercussions. Williams notes that the Comanche's weight requirements were unachievable due to poor management, no party was aware or in control of the aircraft's final weight; there were concerns that, when outfitted with the actual equipment for operations, the Comanche's engines would be incapable of lifting the total weight of the helicopter. Additionally, it was difficult to convince the Army that the development program was out of control, with key individuals failing to realize that insurmountable technical problems even existed. Prized elements of the program, such as software capability and integration, failed to foster confidence with Army overseers; capabilities were seen as unproven and risky while the consumption of up to 40% of the Aviation budget on some years was considered extreme. In the end, it was concluded that the budget would be better spent delivering less risky and more critical needs of the Army.
