The creation of modern military equipment is a complex, lengthy and expensive endeavor. However, modern development and design methods can reduce risks, thanks to which most of the latest projects have been fully implemented. However, there are exceptions. 10 years ago, the US Department of Defense decided to stop all work on the project of a promising reconnaissance and attack helicopter Boeing-Sikorsky RAH-66 Comanche. The project was developed over a long time and cost the Pentagon several billion dollars. However, after analyzing the current situation and prospects, it was closed.
The main prerequisite for the appearance of the RAH-66 helicopter is considered a 1982 report, which analyzed the capabilities of existing US combat helicopters. It argued that the majority of the vehicles in service cannot effectively carry out the assigned combat missions in the context of an armed conflict with the Warsaw Pact Organization. The US Armed Forces needed a new machine capable of overcoming enemy air defenses, finding targets, and also destroying them.
In 1983, just a few months after the report was released, the Pentagon initiated the LHX (Light Helicopter Experimental) program, which aimed to create two helicopters based on a single design. One of them (known as the LHX-SCAT) was intended for reconnaissance and striking, and the second (LHX-UTIL) was seen as a multi-purpose vehicle.
The new program immediately attracted the attention of aircraft manufacturers, since winning the competition implied the signing of several major contracts for the supply of equipment. The ground forces alone, not counting the Air Force and the Marine Corps, planned to order up to 5 thousand new helicopters. It was planned to buy 2,900 LHX-SCAT helicopters to replace the AH-1, OH-6 and OH-58 helicopters, as well as more than 2 thousand LHX-UTIL to replace the outdated multipurpose UH-1.
However, the prospect of obtaining large contracts was complicated by the demands of the military. The army wanted helicopters with unique characteristics, the development of which would require special efforts. It was required to ensure the minimum possible signature in the radar, infrared and acoustic ranges. In addition, the maximum speed of the helicopter was supposed to reach 400-450 km / h, which significantly exceeded the capabilities of all machines that existed at that time. The LHX-SCAT reconnaissance and attack helicopter was supposed to have a single cabin, a set of special equipment and a takeoff weight of about 3800 kg. LHX-UTIL was designed to carry six people or 600 kg of cargo, was to be operated by two pilots and be slightly larger than the SCAT modification.
Four leading US aircraft manufacturers have applied for the LHX competition. Bell, Boeing, Hughes and Sikorsky expressed their desire to develop a promising machine. The specialists of these organizations had their own opinions about the prospects for the development of helicopters, which led to the emergence of several projects with completely different looks. For example, the Sikorsky company offered a machine with coaxial main rotor and pushing tail. This layout was supposed to provide the highest possible flight speed. It is noteworthy that the Sikorsky company continued to develop similar ideas in the future and is now engaged in a similar S-97 project.
During the development of preliminary projects, it turned out that the creation of LHX helicopters with the required characteristics is a rather difficult task, because of which the participants in the competition were forced to join forces. Boeing's helicopter division began working in conjunction with Sikorsky, while Bell specialists began to collaborate with colleagues from McDonnell Douglas, which by that time had become a part of Hughes. In the fall of 1988, the two consortia were awarded contracts for the continuation of the work.
The task of this stage was to determine the possibility of meeting the requirements while maintaining the specified values of take-off weight and cost of the vehicle. In addition, the layout of the helicopters was checked and the first work on the integration of electronic equipment was carried out. At this stage, it turned out that the customer would have to soften the requirements for promising technology. Achieving a maximum flight speed of over 350 km / h proved to be an extremely difficult task from a technical point of view. In addition, studies have shown that low-altitude flight at such speeds will be available only to highly qualified pilots.
The military changed the requirements for maximum speed, and also canceled the development of the LHX-UTIL multipurpose helicopter. Since the mid-eighties, funding for the LHX program has been steadily declining, with several proposals to stop work. Nevertheless, the program continued, albeit reduced. Due to limited financial resources, the Pentagon and the participating companies were forced to apply new methods of working out technical solutions. Most of the ideas and proposals were verified using computer simulations. Some components and assemblies were tested in flying laboratories.
By the spring of 1991, the military had determined who would be involved in the development of the new helicopter, and in the future would begin its serial production. Of the two proposed projects, the one developed by the Boeing-Sikorsky association was chosen. The project received a new name: RAH-66 Comanche. Like some previous American helicopters, the new machine was named after one of the North American Indian tribes. At the same time, the letter RAH was used for the first time in American practice. The helicopter, capable of performing reconnaissance and strike missions with equal success, received the corresponding designation - Reconnaisence and Attack Helicopter.
The contract for the development of the RAH-66 project was signed in April 1991. The choice of the developer made it possible to concentrate all efforts and direct all available funding to only one project, which, in particular, made it possible to begin full-fledged testing of various systems proposed for use on the new machine. It should be noted that this opportunity was extremely important, since the project had a high degree of novelty and required verification or revision of many proposals.
The design of the new helicopter took quite a long time. The first prototype of the Comanche helicopter was rolled out of the assembly shop of the Sikorsky plant only at the end of May 1995. Several months were spent on ground tests. The first flight was supposed to take place at the end of 1995, but in the end it was postponed to January 4, 1996. As time has shown, tests of two built prototypes of a promising reconnaissance and attack helicopter dragged on for eight years.
One of the main requirements for the LHX / RAH-66 helicopter was to reduce the visibility for enemy detection equipment. For this reason, the Comanche helicopter received a number of specific features that distinguish it from other equipment in its class. So, the outer surface of the fuselage of the machine is formed by a large number of rectilinear panels, mated to each other at different angles. The main rotor hub fairing, the tail rotor in the annular channel and the retractable landing gear are used. To accommodate weapons, it was proposed to use internal cargo compartments on the sides of the fuselage. At the same time, the outer covers of the compartments were equipped with pylons for the suspension of weapons. The nose turret with the gun was supposed to turn 180 ° and place the barrels in a special cowl-fairing.
To reduce visibility in the infrared range, the helicopter received an original exhaust gas cooling system. After leaving the engines, they mixed with cold atmospheric air and were thrown out through long slotted pipes located along the sides of the tail boom. Such a system was used for the first time in the United States. Previously, the reduction in heat generated was achieved using special nozzles for the exhaust nozzles.
According to available data, the whole range of measures to reduce the visibility has led to fairly good results. So, in comparison with the AH-64 Apache helicopter, the effective scattering surface has decreased by about 600 times. Comparison of these helicopters in terms of thermal radiation shows a fourfold advantage of the Comanche.
The main structural element of the RAH-66 helicopter is a long box-shaped girder, on which all units and fuselage skin panels are fixed. Most of the power elements and panels of the helicopter skin were made of composite materials based on metals and plastics. An interesting feature of the fuselage design was the skin layout. About 40% of its panels were removable and could be dismantled for servicing indoor units. Damage to the sheathing panels while maintaining the integrity of the power set did not affect the strength of the entire structure.
The fuselage layout with a length of 14.4 m corresponded to modern views on the placement of units. In the bow there was a two-seater cockpit with a common canopy, as well as an equipment compartment and a remotely controlled installation with an automatic cannon. The middle part of the fuselage housed the engines, the main gearbox, some of the equipment and the internal weapons bays. The tail boom was given for the placement of some units. To reduce the visibility, the tail rotor with a diameter of 1.37 m was placed inside the annular channel, and the horizontal tail was installed on the upper part of the keel.
A retractable three-point landing gear was located in the middle and aft fuselage. The main struts were retracted by turning back, the tail - by turning forward. The design of the struts and shock absorbers made it possible to absorb some of the impact energy when landing at an increased vertical speed. In addition, in the parking position, the racks could be partially retracted, reducing the parking height of the machine relative to the full one by 3.4 m.
Initially, the LHX helicopter was supposed to have a single turboshaft engine, but later it was decided to use a more reliable twin-engine power plant. In the mid-eighties, a competition for the development of a promising helicopter engine was launched, in which the development of the LHTEC company won. In the middle part of the fuselage of the RAH-66 helicopter, under the main rotor, two T800-LXT-801 engines with a capacity of 1560 hp were installed. An auxiliary power unit WTS124 is provided, located between the main engines and used as a starter and a means of ensuring the operation of some systems.
In the middle part of the fuselage there was a rotor hub equipped with a fairing. The main rotor with a diameter of 11, 9 m had five blades made entirely of composites. In plan, the blades had a rectangular shape, and were also equipped with a swept tip. It was argued that the main rotor remains operational even when hit by bullets of large-caliber small arms.
In the forward part of the fuselage there was a two-seater cockpit with a tandem arrangement of pilots. An interesting fact is that the pilot was in the front cockpit, and the weapons operator was located in the rear. This non-standard position of the pilots was used in order to provide the maximum possible view from the command cockpit.
Both cabins had the same instrumentation. Both pilots had a set of flight instruments and a full set of controls. The main element of the instrument panels of both cabins were two liquid crystal displays measuring 200x150 mm. The left monochrome screen was intended for outputting video signals from surveillance systems, the right color screen for displaying navigation, flight and tactical information. In addition, there were several smaller monochrome displays in the cockpits. At the bottom of the dashboard, a keyboard was installed to enter the necessary information.
Pilot helmets with a helmet-mounted display system became an important element of the RAH-66 onboard equipment. The helmet-mounted system, depending on the operating mode, could display information about flight parameters, a three-dimensional map, images from surveillance systems, etc. Thus, using the helmet-mounted screen, the commander could receive the information necessary for piloting, and the operator could use weapons without being distracted by the dashboard.
The cockpit had a set of protective equipment. The pilots' seats were covered with light bulletproof armor. To protect against chemical, biological or nuclear weapons, a slight overpressure was maintained in the cockpit. The pressurization system also protected the avionics compartments.
The avionics of the Boeing-Sikorsky RAH-66 Comanche helicopter was located in one nose compartment, located under the operator's cabin, and two tail ones. The avionics of the helicopter used only digital equipment. The basis of the electronic equipment was two digital computers, which ensured the interaction of other equipment and the processing of all the necessary information. To simplify production, the avionics complex was 70% compatible with the equipment of the Lockheed Martin F-22A Raptor fighter.
In view of its reconnaissance mission, the helicopter received a complex of means of detection, communication and data transmission. To determine its own coordinates and the location of the detected objects, RAH-66 received a combined (satellite and inertial) navigation system. The helicopter was supposed to carry a radar station, which is a development of the Longbow system used on the latest AH-64 helicopters. Provided for infrared and television systems for viewing the front hemisphere, as well as a laser for illuminating targets. Optoelectronic systems made it possible to observe a sector with a width of 52 ° in azimuth and 35 ° in elevation.
An interesting feature of the Comancha avionics are the algorithms for work in the search and attack mode. It is assumed that in order to increase survivability, the helicopter should not leave shelters for a long time. In this case, the crew must climb to the required height, scan the terrain and again hide in the folds of the terrain. The equipment "remembers" the collected information, so that the operator can find the target and prepare for an attack without risk. In the memory of the onboard systems, there were signatures of the main targets, objects and equipment of both the enemy and the NATO countries. It was assumed that automatic identification of the type of object would reduce the likelihood of friendly fire.
The RAH-66 helicopter was capable of both independently attacking targets and transmitting information about them to other units. The information was transmitted over an anti-jamming radio channel.
To control the helicopter, it was proposed to use a two-channel digital fly-by-wire system with threefold redundancy. The used EDSU could be used in three modes. In the first, it did not automatically take into account the flight parameters, completely transferring control of the machine to the pilot. In the second mode, the automation, based on data from various sensors, helped the pilot maintain a given speed and altitude, and also controlled the power plant and the parameters of the propellers. The third mode is a full-fledged autopilot that interacts with the weapon control system. In this case, the automatics could independently display the helicopter on a combat course and carry out an attack on the specified target. A separate digital system was used to control the motors.
The built-in armament of the RAH-66 helicopter consisted of one XM301 automatic cannon with a rotating barrel block. The gun had three 20 mm barrels. Cannon ammunition - 320 or 500 rounds. The cannon was mounted on a rotary turret, allowing it to fire at targets in the front hemisphere. When firing at aerial targets, the XM301 cannon is capable of firing up to 1,500 rounds per minute. To hit ground targets, half the rate was used.
An interesting feature of the turret was the used transport position. To reduce the visibility of the helicopter, if necessary, the cannon barrels were turned backward in flight and placed in a special casing. Due to the limited volume inside the nose of the helicopter, the authors of the project had to use an interesting ammunition supply system. A drum magazine for 500 rounds is located under the operator's cab, at a fairly large distance from the gun. The supply of ammunition was carried out using a special conveyor.
Missile weapons were proposed to be transported in onboard cargo compartments. The dimensions of these compartments were determined by the dimensions of the AGM-114 Hellfire air-to-surface missiles and the AIM-92 Stinger air-to-air missiles. In addition, the helicopter could use the Hydra 70 unguided missiles. The development of a new weapon specifically for the RAH-66 helicopter was not planned. For the suspension of weapons, it was proposed to use holders on the side doors-hatches of the cargo compartments. Before using the weapon, the sash had to rise to a horizontal position. Each of them had three suspension assemblies.
To increase firepower, the RAH-66 Comanche helicopter could use the EFAMS harness. It consisted of two wings mounted on the sides of a helicopter. Suspension assemblies on these wings increased the overall ammunition load of the missile armament, making it possible to solve more complex strike missions. At the same time, however, the installation of the wings to some extent reduced the maximum flight speed.
The initial terms of reference for the LHX project involved the creation of a helicopter with a take-off weight of about 3800 kg. The finished Comanche turned out to be much heavier. The empty weight of the helicopter exceeded 4200 kg, the normal take-off weight was 5800 kg. The maximum take-off weight reached 7900 kg, which is more than two times higher than the original requirements. Nevertheless, the terms of reference have been changed several times in accordance with the results of new research and calculations.
The tests, which started at the very beginning of 1996, made it possible to establish the flight data of the new helicopter. The maximum speed reached 324 km / h. After installing the nadvulok radar fairing, which had the shape of a truncated cone, the maximum speed dropped to 317 km / h. The suspension of the additional EFAMS wings also reduced the flight speed by about 20 km / h. Cruising speed without a nad-hub antenna reached 296 km / h. With antenna - 275 km / h. The practical ceiling of the helicopter is 5 km, the static ceiling is 3.5 km. Thanks to economical engines and large internal fuel tanks, the practical range of the helicopter was brought to 900 km. Ferry range - 2335 km.
The RAH-66 project was one of those developments that were influenced by the collapse of the Internal Affairs Department and the USSR, as well as other geopolitical changes in the late eighties and early nineties. Reducing the cost of promising projects affected the development of a new helicopter. So, by the mid-nineties, plans for the purchase of Comanches were reduced from 5,000 to 1,300 units. In the future, the issue of a new reduction in planned purchases was repeatedly raised. In addition, the views of the military were changing. Since the beginning of the design work, the customer has repeatedly changed the requirements for the promising machine. Several times in the mission there was a bias towards reconnaissance or strike capabilities.
Tests, fine-tuning and revision of various systems of the promising helicopter continued until the end of 2003. By this time, discussions on the feasibility of the project began again in the ruling circles of the United States. Supporters of the RAH-66 helicopter appealed to its high performance and versatility. Opponents, in turn, pressed on the financial side of the work. By this time, about 7 billion dollars had been spent on the development and testing of the Comanche helicopter. Taking into account further work and the construction of serial equipment, the total cost of the project could exceed 40 billion.
Other arguments against the new helicopter have been mentioned in numerous discussions. It was noted that the development of the machine dragged on for more than two decades, and repeated improvements to the technical specifications cannot provide the required relevance of the project. In addition, critics recalled the combat use of helicopters in Afghanistan and Iraq, believing that the characteristics of the new RAH-66 are insufficient or redundant for solving certain tasks. It was also noted that reconnaissance operations can be carried out by unmanned aerial vehicles and do not require the creation of specialized helicopters.
The fate of the RAH-66 Comanche project was decided on February 24, 2004, when the leadership of the American Ministry of Defense decided to stop all work. The closure of the project hit the Pentagon's budget. In compensation for the premature termination of development, the military department was forced to pay compensation to Boeing and Sikorsky in the amount of about $ 1 billion.
By the time the project was closed, two prototype helicopters had been built. A few years later, the vehicles with the dismantled equipment were transferred to the US Army Aviation Museum (Fort Rucker, Alabama). The developments on the RAH-66 project were not lost. Ideas and solutions created during the development of a new helicopter are now being used in new helicopter technology projects. Some pieces of equipment were later proposed for use on new modifications of the AH-64 Apache attack helicopter. In addition, in the future it is planned to develop a new helicopter, which will replace the existing technology. Perhaps this machine will become a direct development of the Comanche, which ten years ago did not suit the military and politicians.
