Sikorsky S-97 Raider: and the revolution will come
The first rumors of a “changer” appeared in 2010 - then there was no talk of even a company that would develop a new car. In the July issue, we wrote about the main development trends of modern helicopters, including the Sikorsky S-97 Raider (the name received the prototype), then still hidden behind a veil of secrecy. Now the car is officially presented, the signature stamp "top secret" removed. The blades of the S-97 "grow" from an earlier model, the experimental Sikorsky X2 helicopter, and even from the "old man" S-69, introduced back in 1972. The new machine is a good example of how technology flows from one another, and does not arise out of the blue. The trick is not to use one innovative idea, but in a competent combination of proven concepts. And the revolution will come.
|Sikorsky S-97 Raider||Type: reconnaissance and attack helicopter Developer: Sikorsky Aircraft Corp.||Crew: 2 people (can work in unmanned mode) Capacity: 6 paratroopers|
|Schematic: coaxial with a thrust propeller in the rear . Empty helicopter mass: 4057 kg Maximum take-off weight: 4990 kg Power unit: General Electric YT706 (2600 hp) Main rotor diameter: 10.3 m||Pusher propeller diameter: 2.1 m Cruising speed: 407 km / h Maximum permissible speed: 444 km / h Range: over 600 km Flight duration: 2 h. 40 min.||Practical ceiling: 3048 m Armament: - 7.62 or 12.5 machine gun (or a combination thereof) - 7-charge Mk 4 FFAR missile system or AGM-114 Hellfire installation|
Helicopters have several problems limiting their maximum speed. The first is that when the screw rotates, the retreating blade moves in the direction of air flow, and at a speed close to the flow rate. Because of this, it does not create lift. In the early 1970s, Sikorsky engineers proposed a solution to this problem: to make two coaxial screws with two independent swash plates, capable of changing the angle of attack of the retreating blades. Such a scheme made it possible to level the drop in the lifting force when the blade moves along the stream; in fact, all the lifting force is created by leading blades. In addition, since the helicopter was propelled by two pushing turbojet engines, the main rotors were only supposed to create lift and nothing more. Built on such a scheme, the S-69 set an unofficial world speed record for a helicopter (487 km / h), but did not get into the series due to poor handling, increased vibration and a number of other shortcomings.
But an interesting scheme plus a thrust propulsion haunted Sikorsky engineers, and a quarter of a century later a second similar helicopter appeared, an experimental X2 model. Like the S-69, the experimental machine had two coaxial rotors and a thrust propulsion, but this time not a turbine, but ... a propeller. Here a second problem appeared: when the movement of the tips of the rotor blades approaches the speed of sound, the resistance increases many times. Given the pushing propeller, this problem was solved very simply: starting from a certain moment, the bearing rotors begin to slow down gradually - this does not affect the speed, since it is determined by the pushing screw, and such rotor speeds are simply not needed to create sufficient lifting force!
Only in October 2010, the appointment of X2 became clearer than clear. On a civilian prototype, the techniques used to create a real combat helicopter were worked out. Thanks to this, the S-97 Raider was built in record time - already at the end of 2014 its first flight was scheduled, and for 2015 - sea trials. What is the heir of old Kiowa?
Like the X2, the new helicopter has two coaxial bearing rotors and a pusher propeller of adjustable pitch, which allows you to change the angle of attack of the blades directly during movement, thus better controlling the helicopter depending on flight conditions. The vibration problem that arose on the S-69 was also successfully solved in X2: both the prototype and the combat vehicle use the so-called active vibration control system (AVC), which was previously used on the UH-60M Black Hawk helicopter. The system consists of a set of sensors that measure the frequency of vibration at various points of the fuselage, as well as generators, which, in accordance with the received data, create oscillations of a strictly corresponding frequency. This allows you to reduce vibration in the cockpit and make the flight comfortable for pilots and passengers (landing).
The engine also borrowed the engine from the UH-60M - this is the General Electric gas turbine YT706; all screws - both bearing and pushing - are driven from a single power unit. However, most likely, this is only a temporary step necessary for flight tests and adoption. Over time, Raider will receive its own engine - this was stated by company representatives. This is due to the fact that one of the main advantages of the S-97 over its competitors is its speed.
The declared cruising speed of the helicopter is limited to 407 km / h, although the propellers and aerodynamics do not prohibit accelerating to speeds of more than 500 km / h! For comparison: the fastest multi-purpose helicopter to date and the holder of an official speed record among helicopters, the British Westland Lynx, on August 11, 1986, managed to accelerate to 400.87 km / h, and this achievement has not yet been blocked. Strange, you say, because the X2 was also easily superior to Westland Lynx. Exactly! But the developers of Sikorsky simply did not set themselves the goal of breaking a record - this task along the way, as non-essential, will in any case be solved by S-97.
As in X2, Raider implements a fly-by-wire circuit, that is, an electrical control system. There is no mechanical connection between control devices and actuators - this principle has long been applied in airplanes and partially in helicopters, but the S-97 is the first machine in which there are no mechanical backups at all, in none of the systems. First of all, this was done to facilitate the machine and redistribute its mass; mechanical connections take up too much space. Actually, the lightweight fuselage made of composite materials serves the same purpose.
An additional bonus was the compactness of the helicopter. With a length of 11 and a rotor diameter of 10 m during landing, it requires about 15% less space than its closest competitors in the class, and for combat and rescue operations this indicator is sometimes vital.
Armament on the "Ryder" can be installed very different. In the basic version, this is a 7.62 or 12.5 machine gun (or a combination thereof), as well as a more serious trump card - either a 7-charge system that operates with typical Mk 4 FFAR missiles (2.75-inches), or the well-known AGM-114 Hellfire installation. But, in principle, this is a standard "body kit" in which there is nothing revolutionary.
The helicopter is designed for two pilots, and its cargo compartment may vary depending on the destination. Theoretically, it is capable of carrying six paratroopers, but in fact Sikorsky announces many configurations: combat for missions of various nature, search and rescue, ambulance, etc. This is another goal of the company: a serious restructuring of the US Air Force is planned next year, during which the main attack helicopter AH-64 Apache will slightly change its status. Currently, Apaches are at the disposal of a number of army units, including the National Reserve and the US National Guard. In the future, it is planned to concentrate Apaches exclusively in the army; S-97 claims to be a vacant niche. So Sikorsky managers want to kill two birds with one stone: completely replace the old multi-purpose Bell and partially the more modern shock Apache.
The economic component is especially important for Sikorsky, since the S-97 is unique in the complete absence of state or military funding. This is a private project of a private company, with 75% of investments owned directly by Sikorsky; in addition, another 53 third-party companies were involved in the creation of the helicopter, which served as suppliers of components or simply ... project sponsors.
The subtleties of business
In 2012, the U.S. Army launched the Armed Aerial Scout (AAS) program to develop a compact multi-functional helicopter to replace the OH-58F Vietnamese. But the development of Sikorsky began much earlier, when the Armed Reconnaissance Helicopter (ARH) long-term military helicopter development program was in operation - while at the time of the announcement of the AAS tender, not a single existing S-97 prototype existed in nature, while five other helicopters, claiming in this niche, have already been presented in hardware (developed by Bell, Boeing, Eurocopter, McDonnell Douglas and AgustaWestland). As a result of the study of the issue, the army department came to the conclusion that none of the designs presented meets the requirements of the tender. This meant that essentially the helicopter had to be developed from scratch - to all five competitors. Thanks to this, Sikorsky immediately won out - now it clearly had time to present its system before the others. Did someone know in advance? Maybe.
But the story received another twist: by the end of 2013, the program was unexpectedly curtailed. It would seem that Sikorsky is again at a trough (development is in full swing), but not quite. The army made a “half-hearted” decision - to transfer the AH-64E Apache from the reserves in the part of the active army as an air reconnaissance helicopter (we already mentioned this transfer). And for “Sikorsky” two windows immediately opened - both for the replacement of the “Bells” and for the replacement of the “Apache”. Surely, someone knew something in advance.
Currently, the replacement of the US helicopter fleet is under the Future Vertical Lift (FVL) program, under which it is planned to replace all obsolete aircraft, regardless of destination. Well, the Sikorsky S-97 hit the mark. In fact, this is the only fully prepared and significantly superior to existing analogues multi-purpose helicopter, claiming to appear in the Air Force. The first flight of the new "Bell" (Bell V-280 Valor) is planned only for 2017, in the same year the joint brainchild of Sikorsky and Boeing, the SB-1 Defiant helicopter, will fly. Both of these machines are primarily aimed at replacing the Apache as the main attack helicopter, and the S-97 has no competitors in its multi-purpose niche. There is no point in announcing a tender. But if we forget about all the behind-the-scenes intrigues, this is a really new step in the history of helicopter construction. The machine, which has the proper maneuverability and at the same time able to go at a cruising speed of more than 400 km / h, is two times faster than similar serial models. A new generation helicopter. A very dangerous toy. Let's see how it flies.The article “Black Sikorsky Raider” was published in the magazine Popular Mechanics (No. 12, December 2014).