Experienced SB-1 shortly after rolling out
Boeing and Sikorsky, participating in the Pentagon's Future Vertical Lift (FVL) and Future Long Range Assault Aircraft (FLRAA) programs, are reporting new successes in their joint development, the SB-1 Defiant. During a recent test flight, the machine again improved its speed record and showed compliance with the basic requirement of promising programs. At the same time, the tests are not over yet, and new successes and achievements are expected in the future.
Faster than predecessor
The next flight with the achievement of increased speed took place on June 9 at the West Palm Beach airfield (pc. Florida). In the cockpit of the experienced SB-1 were Sikorsky test pilot Bill Fell and Boeing pilot Ed Hendershade. The main objective of the flight was to accelerate in flight in a straight line with the given modes of operation of the systems, providing for some restrictions.
When accelerating before measuring speed, the power plant worked at half power, which limited propeller thrust. In these modes, the helicopter was able to reach a speed of 205 knots - 379,7 km / h. During acceleration and flight at such a speed, the pilots appreciated the operation of control systems and the power plant.
It is noted that the flight on June 9 demonstrates the compliance of the SB-1 helicopter with one of the main requirements of the FVL program. The objective of the project is to create a promising helicopter that, in terms of its flight characteristics, is superior to the existing serial Sikorsky UH-60 Black Hawk. The maximum permissible speed of the Black Hawk is 360 km / h, or 194 knots. Thus, the new Defianf has already surpassed its predecessor in speed, and the maximum possible performance has not yet been achieved.
Sequence of achievements
Tests of the experienced SB-1 are at a fairly high pace. The overall complexity of the project and emerging problems as a whole do not interfere with their implementation. The helicopter is tested in different modes and gradually shows an increase in flight performance. The achieved results look very interesting, and in the near future it is expected to reach maximum performance.
The SB-1 Defiant prototype began to be built in the middle of the tenth years, and its first flight was originally planned for 2017. Later, the start of the tests was postponed several times due to the need for processing and improvement of the project. The finished car was rolled out of the workshop only in December 2018 and was soon transferred to ground tests.
Helicopter in June record flight
In January 2019, they conducted the first taxiing, jogging and other tests on the ground. The first flight took place on March 21, during which we checked the operation of the systems, maneuverable and limited-speed characteristics. In the following months, SB-1 completed several new flights, including with a gradual increase in speed. In the summer, the car was sent for repair due to a breakdown of the rotor hub. Flight tests resumed on September 24 and continue to this day.
To date, an experienced helicopter, using half the available power, has developed a speed of 205 knots. According to the development companies, using the full power of engines and propellers should ensure a cruising speed of 250 knots (more than 460 km / h) and a maximum speed of at least 500 km / h. The achievement of such indicators is expected within the next few months, however, they cannot yet give an exact date.
In fact, the entire SB-1 Defiant project is built around the idea of increasing the maximum and cruising speeds of the project. To solve this problem, original ideas and designs are used that were previously worked out with the help of experienced Sikorsky X2 and S-97 helicopters.
A decisive contribution to flight performance is the special propeller design. SB-1 is equipped with two counter-rotating coaxial rotors. The design of the screws is optimized for operation at high horizontal speeds. For this, blades of increased stiffness and a special shape with curved edges, as well as with curved tips, are used. The original reinforced hub of the screws covered with a fairing was used.
In take-off and landing modes and at low flight speeds, the rotors are responsible for both the creation of lifting force and translational movement. However, a further increase in traction to increase speed may be associated with negative phenomena on the blades. To avoid this, at high speeds, the helicopter creates a lift with both propellers and a tail stabilizer.
Acceleration to high speeds is carried out using a separate pushing screw in the tail. All three screws of the machine are connected by a common transmission with several operating modes, providing for connecting or disconnecting different units. In all modes, two high-power turboshaft engines are used.
In the experimental configuration, the SB-1 is equipped with engines like Honeywell T55 with a takeoff power of 4000 hp. Helicopters with a different power plant should go into mass production. In the interests of the FVL program, a new General Electric T901 engine with an output of over 5000 hp is created, formerly known as the Future Affordable Turbine Engine (FATE).
According to calculations, the use of T55 or T901 engines provides a cruising speed of 250 knots. The introduction of promising products will bring the flight range to 424 km, as required by the mission on the FVL / FLRAA. In the experimental configuration, the Defiant helicopter has a shorter range. However, in both cases, the helicopter of the new scheme surpasses the army UH-60 in all main indicators.
A helicopter with high flight performance can solve a wide range of problems. Depending on its purpose and configuration, the crew can include up to four people. In a closed cabin, the installation of 12-14 seats for passengers or other equipment, weapons, etc.
It should be recalled that the Sikorsky-Boeing SB-1 Defiant helicopter requires not only high flight performance. This machine should bypass a competitor, get a contract of the armed forces and bring profit to its creators. Her rival in the framework of the FVL / FLRAA competition is the upcoming V-280 Valor tiltrotor designed by a group of companies led by Bell and Lockheed Martin.
Competitor SB-1: Bell-Lockheed Martin V-280 Valor
At the moment, the V-280 project is noticeably ahead of the SB-1. The first flight of this tiltrotor took place in December 2017, and only six months later a horizontal speed of 190 knots (350 km / h) was obtained. In October 2018, a new “personal record” was set - 250 knots. Valor cruising speed is set at 280 knots (518 km / h), and this was the first result in January 2019. Tests are ongoing, new achievements are taking place. The maximum speed of the tiltrotor should exceed 500 km / h.
At the moment, two promising aircraft of the FVL and FLRAA programs show similar flight performance parameters, however, there are significant structural and other differences. SB-1 and V-280 have various advantages over each other, and there is no obvious favorite so far.
According to current plans, flight design tests of two aircraft will continue until 2022. After that, the customer will choose the most successful project for further development, which will last until the end of the decade. Serial production of new equipment will begin only in 2030. Deliveries of the winning machine FVL and FLRAA will allow the replacement of obsolete UH-60s to begin.
Thus, the participating companies of the project did not have much time left to demonstrate the capabilities of their developments. Therefore, we can expect that in the near future new interesting news about those or other achievements. But only in 2022 will it become clear whether the recent SB-1 flight was the next step on the path to orders and series.