At the very end of last year, the American aircraft construction companies Sikorsky and Boeing rolled out the first flight prototype of the promising SB 1 Defiant multipurpose helicopter. The car is already undergoing the necessary ground checks and will soon take off for the first time. In the future - as its creators want it - the helicopter should become the winner of the current competition, and then go into service and go into production. In the meantime, the project remains at the testing stage. It also has to compete with other modern designs.
Programs and projects
Since 2004, the Pentagon and US aircraft building organizations have been implementing several programs aimed at the future renewal of the army's helicopter fleet. The main program is called Future Vertical Lift, and its goal is to create several new vertical takeoff aircraft to replace a number of existing helicopters. Such a replacement will begin after 2030, and by that time the required equipment samples should be created.
Experienced SB 1 after rolling out
One of the FVL subprograms is called FVL-Medium (also known as Future Long-Range Assault Aircraft - FLRAA) and provides for the creation of a helicopter or other medium-class aircraft. The new SB 1 helicopter was created specifically under the FLRAA subprogram and is proposed as a new vehicle for the army. If successful in the current competition, it will be able to replace the existing UH-60 helicopters.
According to the customer's requirements, the FLRAA aircraft must carry at least 12 armed fighters at a speed of 230 knots (430 km / h) for a range of more than 230 nautical miles (425 km). Vertical take-off and landing are set. Two promising FATE (Future Affordable Turbine Engine) 5,000 hp turboshaft engines should be used as a power plant. Before the appearance of such products, the use of serial engines is envisaged.
Sikorsky (now owned by Lockheed Martin) and Boeing have been participating in the FVL program since the middle of the last decade. To meet customer requirements, specific design solutions are required, which is why aircraft manufacturers had to develop and test two experimental samples. The experience of these projects made it possible to start developing a full-fledged vehicle for the army.
In 2008, an experimental Sikorsky X2 helicopter with a non-standard propeller-driven group came out for testing. This car showed a top speed of 460 km / h. In 2015, the Sikorsky S-97 Raider helicopter entered trials with a maximum speed of 445 km / h and a cruising speed of less than 410 km / h. A characteristic feature of the X2 and S-97 machines were two coaxial main rotors and a tail pusher propeller, which was responsible for gaining horizontal speed. During the tests, such a scheme and its individual elements showed their capabilities and confirmed the calculated characteristics.
SB 1 Defiant project
In 2013, the customer launched a new phase of the program, involving the development and construction of technological demonstrators. Soon the number of FVL participants decreased, and now only the Sikorsky and Boeing consortium, as well as Bell Helicopters, are engaged in the development of new equipment. It is curious that Lockheed Martin is taking part in both new projects as a full-fledged participant or subcontractor.
On the basis of ideas and solutions of existing experimental projects, as well as using ready-made units, a new multi-purpose helicopter called SB 1 Defiant was developed; it is this machine that must participate in the Pentagon competition and apply for a future contract. The development of "Daring" was noticeably delayed, which is why its creators did not manage to meet the specified deadlines. The technology demonstrator was required to be built before the end of 2017, but its actual rollout took place only a year later.
Main design features
The first flying prototype SB 1 with serial number 0001 and registration N100FV was taken out of the assembly shop on December 28, 2018. Soon after, ground checks of onboard systems started. At the beginning of January, the first test start of the engines was reported; a few days later, the runway began. In the coming weeks, Boeing and Sikorsky are expected to complete ground checks and launch a flight test phase. The exact date of the first flight has not yet been announced.
Future-proof design
The Sikorsky Boeing SB 1 project proposes the construction of an aircraft of a special design that ensures high flight performance. The basic decisions required 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 receives a streamlined composite fuselage, combining high strength and low weight. The fuselage layout, in general, repeats the solutions of other projects. The nose of the fuselage and the central compartment are given under the cockpit for the crew and passengers. The main elements of the power plant are placed above the cargo volume. The tail boom accommodates the transmission for the pusher propeller.
As in previous projects, the glider has no wings, but a developed tail unit is used. A large-span stabilizer is used, equipped with keel end washers. A vertical plane is placed under the fuselage. All empennage planes are equipped with rudders or made all-turning. These rudders are proposed to be used for high-speed flight control.
In the future, the SB 1 helicopter should receive a pair of turboshaft engines developed under the FATE program. Prior to their appearance, the prototype will use serial Honeywell T55s with a capacity of less than 4 thousand hp. The lack of power in comparison with the calculated one should worsen the flight performance, but in this case the “Daring” 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 performance, although they will reduce the flight range.
The motors drive a pair of coaxial rotors. The propellers, along with the hub and related equipment, were borrowed from the experimental S-97 Raider with minimal modification. The propellers have four blades and are fixed on a common hub. Due to the characteristic loads during high-speed flight, the carrier system has a structure of increased rigidity. For ease of storage and operation on ships, the propeller blades are foldable. According to the project, the hub elements should be covered with light fairings, but the prototype has not yet received them.
The tail propeller is responsible for acceleration to the required speeds. It has eight controlled-pitch blades and is driven by a separate transmission with power take-off from the main gearbox.
A new fly-by-wire control system has been developed for the SB 1, providing control over the operation of engines, propellers and other systems. An important feature of such an EDSU is the maximum automation of processes, as well as the presence of the so-called. active vibration control system. Automation will be able to independently detect unwanted vibrations of the structure and change the operating mode of the power plant and the propeller to eliminate them. Getting rid of vibrations should have a positive effect on the resource of the structure and its service life.
The helicopter receives a three-point landing gear. In the central part of the fuselage, there are two retractable struts. The third wheel is placed inside the tail ventral keel. The low chassis height should facilitate the entry and exit of people by eliminating the need for ladders or ladders.
A two-row, four-seat cockpit is provided in the forward fuselage. A "glass cockpit" is used with a full set of modern equipment for navigation and control of all onboard systems. Behind the pilots is a payload volume that is tailored to customer requirements. The helicopter is capable of transporting at least 12 fully equipped fighters.
So far, the transport version of the SB 1 has no weapons. However, advertisements feature images of hypothetical production helicopters with machine gun or grenade launchers in doors and windows. Moreover, such weapons are considered only as a means of supporting the landing.
In its current form, the prototype of the SB 1 Defiant helicopter has a take-off weight of about 14.5 tons - almost three times more than the previous S-97. In the near future, flight tests will be carried out aimed at establishing the real characteristics of the equipment. The development companies claim that the machine will fully meet or exceed customer requirements. So, the estimated maximum speed with temporary T55 engines should reach 450-460 km / h. With the new FATE motors, this parameter will remain at the same level, but the flight range will reach the required values.
Near and distant future
So far, the main concern of specialists from Sikorsky and Boeing is the completion of the necessary ground tests and preparation for future test flights. Not so long ago, the first start of the engines and the scrolling of the propellers took place, and in the near future the experienced SB 1 will take to the air for the first time. Testing is planned to continue over the next several 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 "Daring". What it will be is unclear, but the advertisement has already shown its possible appearance. The combat "modification" can get a narrowed fuselage with a two-seat tandem cockpit and without a central cargo compartment. A turret with artillery weapons can be installed under the nose, and planes with suspension nodes for missile and bomb weapons are located on the sides. Even the calculated characteristics of the shock version of the SB 1 are still unknown.
According to the optimistic plans and forecasts of Sikorsky and Boeing, their new helicopters in the distant future should enter service with the US Army Aviation. The transport SB 1 Defiant is being considered as a replacement for the existing UH-60. Its combat modification will be able to claim the niche currently occupied by the AH-64.
Transport SB 1 (foreground) and attack helicopter at its base
It is not known whether the consortium will participate in the competition for contracts for other FVL subprograms. In addition to the UH-60 and AH-64, the army plans to replace the OH-58 and CH-47 types in the future. As far as is known, Boeing and Sikorsky are considering the possibility of introducing developments on the X2 / S-97 / SB 1 themes into the field of heavy transport helicopters. Perhaps later it will become known about a similar replacement for the lungs OH-58.
Struggle for a contract
Sikorsky and Boeing with the SB 1 Defiant project apply for a Pentagon contract, according to which at least several hundred production vehicles will be built. However, other aircraft manufacturers can get a profitable order. Another high performance aircraft is being developed in parallel under the FVL-Medium / FLRAA program. Bell Helicopters and Lockheed Martin offer the V-280 Valor.
An alternative project involves the construction of a tiltrotor with a pair of rotary screws and a fixed wing. In terms of its flight and operational characteristics, the V-280 should be close to SB 1 and meet customer requirements. While the outcome of the confrontation between the two machines remains in question, but the development of Bell and Lockheed Martin has a slight advantage: the experienced V-280 was built back in 2017 and took off for the first time in December of the same year. The first prototype SB 1 was rolled out only a year later. It is possible that the developers of the Valor car will be able to reasonably dispose of their lead time, and this will affect the results of the competition.
However, both promising aircraft, claiming to be the UH-60 in the US Army Aviation, are still at the testing stage. They have to go through testing and debugging, and then demonstrate their best qualities to the future customer. The Pentagon, in turn, will have to make a difficult choice. The military will have to choose between a long-known and tested, but not without flaws, tiltrotor scheme and a completely new architecture of a helicopter with a main and pusher rotor. 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 car, after which it will begin preparing for future mass production. The process of replacing existing helicopters of the army aviation will start by 2030 and will give real results by the middle of the decade. So far, we can assume that both promising models have equal chances of being adopted for service and entering the troops. Time will tell which one the Pentagon will choose.
