Boeing–Sikorsky RAH-66 Comanche

The Boeing–Sikorsky RAH-66 Comanche was an advanced five-blade armed reconnaissance and attack helicopter designed for the United States Army. The RAH-66 program was canceled in 2004, before mass production began, after nearly US$7 billion was spent on the program.

During the early 1980s, the U.S. Army began formulating a requirement for the 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.

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 the requirement was changed to a reconnaissance helicopter. In October 1988, 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 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.

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 or 2.1% to meet its 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 continued flight testing from 23 May 2002, including testing of night vision and weapon systems, until 2003. During testing, the Comanche cruised at 162 kn, a "dash speed" of 172 kn, 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, which 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 Fiscal 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 for which the Comanche was being developed. 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 actual equipment required 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 had serious troubles, as key individuals failed to realize the existence of insurmountable technical problems. 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 its budget would be better spent delivering less risky and more critical needs.

The GAO recorded that an Army spokesperson stated that "the program's costs could no longer be justified". Author Cindy Williams said of the Comanche: "The rationale for cutting Comanche... is twofold. First, the doctrinal niche that the Comanche occupies is unnecessary in the near term and probably not viable in the longer term. Secondly, as with all rotary-wing aircraft, the Comanche is a voracious consumer of strategic airlift."

Sikorsky and Boeing say that factors outside their control, like budget cuts, "requirement creep," and a long development period caused problems with the Comanche and not team dysfunctionality. Under the Comanche program, each company built different parts of the aircraft. The two companies are teaming up again for the Future Vertical Lift prototype called SB-1 Defiant, where employees from both companies will work together.

Design
The RAH-66 was powered by two LHTEC T800 turboshaft engines. Its fuselage was 43 ft long and made of composite material. It 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 1200 nmi would allow it to fly to battlefields overseas on its own. The Comanche was specifically tailored to the role of armed scout to replace the U.S. Army's OH-58D Kiowa Warrior, which is an upgraded version of a Vietnam War-era observation helicopter. The Comanche was smaller and lighter than the AH-64.

The RAH-66 was intended to be a stealth helicopter; it incorporated multiple techniques to reduce its radar cross-section (RCS) and other areas of visibility. Its outer surfaces were faceted and had radar-absorbent material (RAM) coatings and infrared-suppressant paint applied; with these measures, the Comanche's RCS was 360 times smaller than the AH-64 Apache attack helicopter. The Comanche's acoustic signature was noticeably lower than comparative helicopters; this was partly achieved through the all-composite 5-blade main rotor and pioneering canted 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 flight control 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 was armed with a 20 mm three-barrel XM301 cannon under its nose and could internally carry six AGM-114 Hellfire or twelve AIM-92 Stinger missiles split evenly between the two retractable weapons pylons. The Comanche could also externally carry four Hellfire or eight Stinger missiles on each of its stub wings but with a reduction in the effectiveness of stealth technologies.

Aircraft on display
Both prototype airframes 94-0327, 95-0001, are located at the United States Army Aviation Museum at Fort Rucker, Alabama.