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Light Helicopter Experimental (LHX)

The Light Helicopter Experimental (LHX) combat helicopter program was initiated in 1983 to replace the Army's rapidly aging fleet of UH-1, OH-58A Kiowa scout and AH-1 Cobra light attack helicopters. At the time, as many as 6,000 helicopters were envisioned. The Scout/Attack (SCAT) was the design driver; the utility was to be derived from the SCAT. To fulfil the missions undertaken by the existing fleet, different LHX models were to be equipped with a large variety of new technologies and mission equipment packages. A light survivable, lethal, armed reconnaissance helicopter, the LHX combat helicopter was to have greater capabilities, new sensors, millimeter wave radar, and other advance features in a high visibility cockpit. Maximum use was to made of computer-aided design of the LHX and systems as an integrated whole.

A Scout/Attack version would be configured as a helicopter which can be tailored to perform both light attack and armed reconnaissance mlssions. The Scout/Attack version would replace the aging AH-l, 0H-58A/C and OH-6A helicopters. It would complement the OH-58D. The SCAT is the more sophisticated of the two, and it was to be a single seat helicopter whose armament would include and it is to be a single seat helicopter whose armament will include Hellfire antitank missiles, air-to-air missiles, and a gun system. The utility version of LHX would possess extensive commonality with the Scout/Attack version to include the same dynamic components (engine, transmlsslon, rotor, etc), and many common subsystems and mission eyulpment. The utility version will transport troops, unit commanders and cargo. It would complement the UH-60 squad-carrying troop assault helicopter and replace the WI-1 helicopter. The utility version would have two seats; it would carry air-to-air missiles for self-defense, and it would not have the target acquisition equipment of the SCAT. The Army planned to buy 2,000 SCATS and 2,500 utility helicopters.

The Army identified the need for the LHX in its Army Aviation Mission Area Analysis completed m January 1982. This study concluded that the current fleet of Army light helicopters would be unsupportable and nonsurvlvable on the future battlefield. An Army Aviation Systems Program Review in March 1982 endorsed the Mission Area Analysis and made a recommendation to replace portions of the current fleet of Army helicopters with the LHX. A LHX pecial working group was formed in January 1983 to develop the framework of the LHX rogram, Six Army organizations1 were represented on the special working group. The Department of the Army approved the Operational and Orgamzatlonal Plan and the Justificatlon for a Major Systems New Start in May 1983, and included the necessary LHX program funding m its fiscal year 1985 budget and outyear funding profile.

During the concept exploration phase, the acquisition strategy was developed, system alternatives were proposed and examined, and the material requirements document was refined to support the subsequent acquisition phases. To support the Army's concept exploration activities, competitive preliminary design contracts were awarded in September 1983 to the four major helicopter firms - Bell Helicopter Textron, Sikorsky Aircraft, Boeing Vertol and Hughes Helicopter to define specific aircraft system configurations (point designs) Contracts were also awarded m December 1983 to define the advanced/integrated cockpit design and architecture and demonstrate the feasibihty of a single-pilot LHX Scout/Attack through full-mission simulations. These contracts were awarded to the four major helicopter firms and to IBM.

In 1984 the Bell Advanced Tilt Rotor (or BAT) was a lightweight advanced, single seat, tilt-rotor aircraft proposed by Bell in response to the US Army's Light Helicopter Experimental programm Development of the BAT had to be abandoned due to new LHX requirements, especially in the matter of weight (LHX had to be under 3150kg). The BAT was a small aircraft, with a butterfly tail unit.

In June 1985, Sikorsky and Boeing teamed to begin studies in the Army's Light Helicopter Experimental (LHX) competition. The Sikorsky (S-75) Advanced Composite Airframe Program (ACAP) was an all-composite Sikorsky early LHX proof of concept aircraft. Composite materials were used to replace metal to provide greater strength, lighter weight, lower manufacturing costs, and reduce maintenance costs. The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts.

The LHX speed requirement was not defined early on. However, the speed issue was resolved when the Army decided to develop a conventional LHX helicopter. The Army Chief of Staff decided on March 4, 1985, to develop a conventional hehcopter and eliminate other design concepts prevloudy being considered. The principal factor which prompted this decision was the risk mvolved m developing the other design concepts (that is, compound, advancing blade, and tilt rotor). Other factors were cost, weight, and design needed to meet required performance capabilities.

The original concept of the LHX program was to produce a one-man helicopter that could do more than a two-man aircraft. Having a single crew cockpit necessitates a higher level of automation than does having a two-member crew, as there must be greater interaction between sensors and more highly automated flight controls to reduce the work load of the single crew member. However, it appeared that the LHX's design risks and sophistication are more heavily influenced by the mission requirements than by going to a single-member crew.

The Sikorsky (S-76) Helicopter Advance Demonstrator of Operators Workload (SHADOW) had a single-pilot advanced cockpit grafted to its nose. The purpose was to study the MANPRINT or human engineering interface between the pilot and the cockpit controls and displays. The cockpit was the prototype of a single-pilot cockpit designed for use on the prototype RAH-66 Comanche armed reconnaissance helicopter. The cockpit was designed so sensors would feed data to the pilot through helmet mounted displays. The MANPRINT study determined that single-pilot operation of the Comanche was unsafe, and would result in pilot overload. As result of this 1985 study, the Comanche was designed to be operated by a crew of two.

Early program documents indicate that the Army identified the attack role (anti-armor) as the Comanche's primary mission. During development, the Army again emphasized the importance of the Comanche's attack capabilities. For example, the Army's decision to switch to a two-seat aircraft was prompted largely because one pilot could not successfully accomplish all of the tasks related to the attack mission. Studies indicated that available technology would not reduce the work load to an acceptable level so that a single pilot could fly the aircraft in combat, identify targets, and fire weapons at the same time.

The LHX baseline acquisition strategy approved by senior Army officials included competition for the LHX air vehicle in both the full-scale development and production phases. Two LHX development contracts were to be awarded leading to a fly-off to select the winnmg design. The prototype to be used for the fly-off was to be an air vehicle produced during a pilot production program to be incorporated mto the full-scale development phase. Full production competltlon would be mtroduced not later than production lot number 3. If the winner of the fly-off was a team consisting of two firms capable of producing the LHX, these two firms would compete for the production contracts. In the event the winner of the fly-off did not consist of a team with two firms capable of producing the LHX, the loser of the fly-off would become the alternate competitive production source The winner of the fly-off would be responsible for qualifying the loser to produce the winning design for full production competition by lot number 3.

By 1986 affordability considerations had caused the Department of the Army to significantly reduce its planned LHX research and development funding amounts in the Army's fiscal years 1987 to 1991 funding guidance submitted to DOD. This reduced budget profile did not provide adequate funds to implement the baseline acquisition strategy which was to carry two LHX air vehicle developers through the entire full-scale development phase, have a fly-off, and select the best design for production.

On July 19, 1985, AVSCOM awarded two full-scale development contracts for engine development. Both contracts were awarded under teaming arrangements, one to the AVCO Lycoming/Pratt & Whitney team for $240 million and the second to the Garrett/Allison team (Garrett Turbme Engine Company/Allison Gas Turbine Division of General Motors) for $264 million. Each team was to compete its design against the other during early development up to a preliminary flight rating. At that time, the Army would select one team - based on bench test demonstrations - to complete the engine's development. At the completion of the development phase both engine manufacturers of the survivmg team are to be capable of producing productron engines. The Army then intends to require both engine manufacturers of the survlvmg team to produce approximately equal quantities of engines.

The Army established unit flyaway cost goals for the LHX very early in the program. These goals were $6 million for the Scout/Attack (SCAT) version and $4 million for the utility version (in fiscal year 1984 dollars), or a fleet average of $6.3 million. The Army has held fast to the unit cost goals, despite early indications that the goals could not be met without sacrificing capability. The Army has conducted several requirements scrubs, including deletion of substantial amounts of mission equipment from the utility version, to keep estimates within the cost goals. The Army estimates were based on production buys of 480 aircraft per year, which preliminary assessments indicated were not affordable. Lower production rates would increase unit costs. At 480 aircraft per year, unit flyaway costs for the SCAT version in 1984 dollars are estimated at $6.02 million per aircraft; at 360 per year, $6.09 million per aircraft; at 240 per year, $6.42 million per aircraft.

As of February 1987, unit flyaway costs had increased 15 percent for the SCAT and 35 percent for the utility version. SCAT unit costs increased primarily because of the need to increase aircraft weight to satisfy mission requirements. The overall reduced number of aircraft, and particularly the procurement of fewer SCATS, has also increased SCAT unit costs. The utility version's unit cost increase is due mainly to the Army's decision to outfit it with the same mission equipment as the SCAT with some exceptions.

Research and development cost estimates remained fairly constant through 1986 since the first estimates in 1983. The 1984 constant dollar estimate has remained at $2.6 billion. The escalated research and development estimate rose from $3.1 billion in 1983 to $3.2 billion as of 1986. The increase was due primarily to delays in starting full-scale development because funds obtained for the advanced rotorcraft technology integration (ARTI) program were less than expected.

By 1987 Research and Development cost had increased to $3.8 billion, due mainly to changes in the acquisition strategy suggested by DOD's Defense Science Board, which extended the LHX team competition through full-scale development to include a competitive flight test. The previous strategy had called for selecting one contractor before beginning prototype fabrication. Also contributing to cost increases were the Army's decisions to build a two-seat SCAT prototype in addition to a one-seat prototype.

By 1987 the Army learned that the performance necessary from the optical sensors to fully automate the targeting function for the single pilot may not be available for application to the initial LHX helicopters. The Army considered developing a radar sensor to complement the optical sensors available for the LHX to achieve full automation, but determined the additional equipment to be too costly and heavy for inclusion on the initial LHX helicopters. These factors, combined with an assessment by the Defense Science Board, have raised some doubts about achieving the single seat objective and have led to the addition of a two-seat version to the development program.

In addition to automated targeting technologies, other areas where performance expectations had been lowered include the quality of the visual displays, digital map, automatic hover-hold, and aircraft survivability equipment. Performance reductions reflect tradeoffs due to cost, weight, technical risk, or a combination of these. The original weight goal for the one-seat SCAT was 8,500 pounds. By late 1987 the goal for the same version is 9,500 pounds. A two-seat version would weigh more.

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Page last modified: 23-02-2020 16:39:43 ZULU