Programs and projects
Since 2004, the Pentagon and US aircraft building organizations have been implementing several programs whose goal is the future renewal of the army's helicopter fleet aviation. The main program is called Future Vertical Lift, and its goal is to create several new vertical take-off aircraft to replace a number of existing helicopters. Such a replacement will begin after 2030, and by this time the required equipment samples should be created.
One of the FVL subroutines is called FVL-Medium (also using the designation Future Long-Range Assault Aircraft - FLRAA) and provides for the creation of a helicopter or other middle-class aircraft. The new SB 1 helicopter was created under the FLRAA subprogram and is proposed as a new vehicle for the army. If successful in the current competition, he will be able to replace the existing UH-60 helicopters.
According to customer requirements, the FLRAA aircraft must carry at least 12 fighters with armament at speeds of 230 nodes (430 km / h) over distances greater than 230 nautical miles (425 km). Vertical take-off and landing are set. As a power plant, two promising FATE (Future Affordable Turbine Engine) turboshaft engines with an 5000 horsepower rating should be used. Before the advent of such products, the use of serial engines.
Sikorsky (now owned by Lockheed Martin) and Boeing have been participating in the FVL program since the middle of the last decade. To fulfill customer requirements, specific design solutions are needed, which is why aircraft manufacturers had to develop and test two experimental samples. The experience of these projects has allowed to start developing a full-fledged vehicle for the army.
In 2008, an experimental Sikorsky X2 helicopter with a non-standard propeller group came out on trial. This car showed a maximum speed of 460 km / h. In 2015, the Sikorsky S-97 Raider helicopter with a maximum speed of 445 km / h and cruising less than 410 km / h came out on trial. A characteristic feature of the X2 and S-97 machines were two coaxial rotors and tail pusher propeller responsible for the horizontal speed set. During the tests, such a scheme and its individual elements showed their capabilities and confirmed the design characteristics.
Project SB 1 Defiant
In 2013, the customer launched a new phase of the program, involving the development and construction of technology demonstrators. Soon the number of FVL participants was reduced, and now only the Sikorsky and Boeing consortium, as well as Bell Helicopters, are engaged in the development of new technology. It is curious that Lockheed Martin is participating in both new projects as a full-fledged participant or subcontractor.
Based on the ideas and solutions of existing pilot projects, as well as using ready-made units, a new multi-purpose helicopter was developed under the name SB 1 Defiant (“Brash”); It is this machine that must participate in the Pentagon competition and qualify for a future contract. The development of the “Bold” was noticeably delayed, which is why its creators failed to meet the deadlines. The technology demonstrator was required to be built before the end of 2017, but its actual rolling out took place only a year later.
The first SB 1 flight prototype with 0001 serial number and registration N100FV was taken out of December 28 2018 assembly workshop of the year. Soon after, ground tests of onboard systems started. In early January, the first trial engine start was reported; a few days later began running on the runway. In the coming weeks, Boeing and Sikorsky experts are to complete ground tests and launch a flight test phase. The exact date of the first flight has not yet been called.
The Sikorsky Boeing SB 1 project proposes the construction of an aircraft of special design that provides high flight characteristics. The main decisions needed to obtain such results are directly borrowed from previous pilot projects. In addition, we are talking about the use of some already tested components and assemblies.
SB 1 gets a streamlined composite fuselage that combines high strength and low mass. The layout of the fuselage, in general, repeats the decisions of other projects. The nose of the fuselage and the central compartment are given under the cockpit for the crew and passengers. Above the cargo volume are the main elements of the power plant. The tail rail accommodates the transmission for the pusher propeller.
As in previous projects, the airframe does not have wings, but it uses advanced tail. A large span stabilizer equipped with keel end washers is used. Under the fuselage placed a vertical plane. All planes of plumage are equipped with rudders or made all-turning. These rudders are proposed to be used for control during high-speed flight.
In the future, the SB 1 should receive a pair of turboshaft engines developed under the FATE program. Prior to their appearance, the prototype will use serial Honeywell T55 with a capacity of less than 4 ths. Hp. The lack of power in comparison with the calculated one should worsen the flight performance, but even in this case the “Bold” will be able to pass some of the necessary checks. It is expected that less powerful engines will not have a negative impact on speed characteristics, although they will reduce the flight range.
Engines drive a pair of coaxial rotors. The screws, along with the sleeve and related equipment with a minimum of refinement were borrowed from the experimental machine S-97 Raider. The screws have four blades and are fixed on a common hub. In connection with the characteristic loads during high-speed flight, the carrier system has a design of increased rigidity. For easy storage and operation on ships, the propeller blades are foldable. According to the project, sleeve elements should be closed with light fairings, but the prototype has not yet received them.
Overclocking to the required speeds is the tail pusher screw. It has eight blades with controlled pitch and is driven by a separate transmission with power take-off from the main gearbox.
For SB 1, a new electrical remote control system has been developed that provides control over the operation of engines, propellers and other systems. An important feature of this EDSU is the maximum automation of processes, as well as the presence of so-called. active vibration control system. Automation will be able to independently detect unwanted vibrations of the structure and change the mode of operation of the power plant and the screw to eliminate them. Freedom from vibrations should have a positive impact on the life of the structure and its service life.
The helicopter gets a three-point chassis. In the central part of the fuselage there are two retractable racks. The third wheel is placed inside the tail ventral keel. Low chassis height should facilitate the landing and disembarkation of people, eliminating the need for ladders or ladders.
In the forward part of the fuselage there is a two-row four-seater cockpit. A “glass cabin” with a full set of modern equipment is used to navigate and control all onboard systems. Behind the pilots is the volume for the payload that meets the requirements of the customer. The helicopter is capable of carrying at least 12 fighters with full gear.
While the transport version of the SB 1 has no weapons. Nevertheless, images of hypothetical serial helicopters with machine-gun or grenade launchers in doors and windows appear in the promotional materials. In this case weapon considered only as a means of supporting the landing.
In its current form, the prototype model of the SB 1 Defiant helicopter has a take-off mass of about 14,5 T - almost three times the previous S-97. In the near future, flight tests will be held to establish the real characteristics of the equipment. Development companies claim that the machine will fully comply with customer requirements or even surpass them. Thus, the calculated maximum speed with temporary engines T55 should reach 450-460 km / h. With the new FATE engines, this parameter will remain at the same level, but the flight range will reach the required values.
Immediate and distant future
So far, the main concern of the Sikorsky and Boeing specialists is the completion of the necessary ground tests and preparation for future test flights. Not so long ago, the first launch of the engines and the scrolling of the screws took place, and in the near future, the experienced SB 1 will rise into the air for the first time. Tests are scheduled to continue over the next few years. Under the supervision of the military, the prototype will have to demonstrate its capabilities, even if it is incomplete.
The authors of the project are already working on its development. First of all, it is planned to create an attack helicopter on the basis of the “Daring”. What it will be is not clear, but its possible appearance is already shown in the advertisement. Combat "modification" can get a narrowed fuselage with a double tandem crew cabin and without a central cargo compartment. Under the nose can be installed turret with artillery weapons, and on the sides are planes with suspension nodes for rocket and bomb weapons. Even the calculated characteristics of the shock version of the SB 1 still remain unknown.
According to the optimistic plans and forecasts of Sikorsky and Boeing, their new helicopters in the distant future should go into service with US Army aircraft. The transport SB 1 Defiant is considered as a replacement for the existing UH-60. Its combat modification will be able to claim the niche now occupied by the AH-64 machines.
Whether the consortium will participate in the fight for contracts under other FVL subprogrammes is unknown. In addition to UH-60 and AH-64, the army plans to replace machines of the types OH-58 and CH-47 in the future. As far as we know, Boeing and Sikorsky are considering the possibility of incorporating developments on the X2 / S-97 / SB 1 topics into the sphere of heavy transport helicopters. Perhaps later it will become known about a similar replacement for light OH-58.
Fight for contract
Sikorsky and Boeing companies with the SB 1 Defiant project are claiming a Pentagon contract, according to which at least several hundred production vehicles will be built. However, a profitable order can get other aircraft manufacturers. Under the FVL-Medium / FLRAA program, another high performance aircraft is being developed in parallel. Bell Helicopters and Lockheed Martin offer the V-280 Valor.
An alternative project involves the construction of a convertoplane with a pair of turn screws and a fixed wing. In terms of its flight and performance characteristics, the V-280 should be close to the SB 1 and comply with customer requirements. So far, the outcome of the confrontation between the two cars remains in question, but the development of Bell and Lockheed-Martin has a slight advantage: an experienced V-280 was built in 2017 year and took to the air for the first time in December of the same year. The first prototype SB 1 rolled out only a year or more. It is possible that the developers of the machine Valor will be able to reasonably dispose of their margin in time, and this will affect the outcome of the competition.
However, both promising aircraft, claiming the place of the UH-60 in the US Army Aviation, are still at the testing stage. They will be tested and refined, and then demonstrate their best qualities to the future customer. The Pentagon, in turn, will have to make not the easiest choice. The military will have to choose between the well-known and tested, but not without flaws, convertible map scheme and the completely new architecture of the helicopter with the main rotor and pusher propeller. Which of the two schemes and machines based on them will interest the customer is a big question.
According to current plans, further work on the SB 1 and V-280 projects will continue for several more years. At the beginning of the twentieth year, the Pentagon will choose a more successful machine, after which its preparation for future mass production will begin. The process of replacing the existing helicopters of the army aviation will start by 2030 and will give real results by the middle of the decade. For the time being, it can be considered that both prospective models have equal chances of being put into service and entering the troops. Which of them will choose the Pentagon, time will tell.
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