Racing with the laws of physics
Despite their somewhat extravagant appearance, helicopters are actually more conservative than their winged “brothers” - planes. Of course, revolutions did occur in the world of helicopter manufacturing, but they were not as frequent as in the world of "large" aviation (which is just the transition from propeller to jet aircraft). Even if we look at the screw machines of the last decades, we will see that the differences between them are much smaller than the similarities. The changes that were introduced concerned mainly on-board electronics and the use of new composite materials in the design. We can say that stealthTechnology Helicopter world passed by: in contrast to the same fifth-generation fighters, rotorcraft do not need cardinal stealth, and besides, any stealth is a very expensive “toy”. In the case of helicopters, technology risks making them too expensive.
The military and civilian helicopters that exist now have reached, one might say, the pinnacles of their evolution. This, however, does not mean that they have no shortcomings. One example is increased fuel consumption (specific fuel consumption). As a result, a higher flight cost per passenger-kilometer or unit mass of the transported cargo, in comparison with airplanes. Roughly speaking, helicopters seem economicalbut they are not. Another problem closely related to the first is the relatively low speed. Alas, the laws of aerodynamics are such that to make a "classic" rotorcraft much faster, without changing its concept, will fail. The newest Russian Mi-38 has a maximum speed of 320 km / h, and cruising - 295 km / h. This is a lot by the standards of helicopters, however, as you can easily see, the difference is not so great when compared with the Soviet-era rotorcraft. For a number of versions of the Mi-8, the maximum speed could reach 260 km / h. By the way, the new American convertiplane Bell V-22 Osprey, with all its drawbacks, such as complexity, unreliability and high cost, can develop 565 km / h. Feel the difference, as they say.
Bell V-22 Osprey
However, the concern of domestic experts is not the exotic Osprey, but the fundamentally new creations of Europe and the USA. We are talking about helicopters equipped in the appendage to the rotor with a pushing screw or, for example, two pulling screws. That is, we are talking about "helicopter-planes", but not as complex and moody as the V-22 tiltrotor. These include the Sikorsky S-97 Raider, an American military intelligence officer, who received a coaxial rotor design uncharacteristic of the American aircraft industry, as well as one pushing screw at the rear of the fuselage.
Sikorsky S-97 Raider
Another example is the “peaceful” European Eurocopter X3, which was equipped with additional pulling propellers on the sides. The car looks a little ridiculous, but this does not negate the fact that it can fly at a speed of almost 500 km / h! No other helicopter is capable of this. And even more so, built in the framework of the classical scheme. The X3 itself is experimental and it won’t go into production. However, based on the experience gained, Airbus wants to build a hybrid Racer: conceptually similar, but having propellers not of a pulling, but of a pushing type.
However, it is not enough just to “attach” one additional screw to make the helicopter faster. “At maximum flight speed, the tip of the“ advancing ”blade approaches a sound barrier, and the effect of a“ wave crisis ”arises on it - the drag increases sharply. On the "retreating" blade increases the area of the reverse flow. The swing movements of the blades become more intense, and it reaches supercritical angles of attack. There is a "stall", and the car loses control. Pilots call this phenomenon “felling”, ”says Vyacheslav Poluyakhtov, associate professor at the Department of Aerodynamics and Flight Dynamics of the Syzransky VVAUL (now a branch of the Air Force Research Center VVAS). This is only part of the problems and contradictions.
“Hey, come on, man, with a breeze ...”
In Russia, affairs with high-speed helicopters are, frankly, bad. The only thing that exists in iron is a somewhat strange flying laboratory, performed as part of the PSV (Perspective High-Speed Helicopter) program. It was created on the basis of the Mi-24K and is referred to in a number of sources as a “demonstrator of a promising high-speed helicopter." But it sounds a little too ambitious. In fact, the car is simply “licked” by the Mi-24 (the original cockpit light is noteworthy) and does not pretend to act as a base for a technological breakthrough. In the presented form, the helicopter, of course, will not go into the series either. Yes, and this is not necessary: the Mi-24 has long been outdated as a base for promising machines of the future. “The main goal of the project is to create a scientific and technical reserve for increasing the flight speed of helicopters by 1,5 times in comparison with serial machines that are currently produced,” the Russian Helicopters said in a statement. By the way, almost nothing is heard about the work under the PSV. Back in 2015, they reported the first flight of a flying laboratory. The project was then often referred to in the context of future plans. On this, in general, that's all. Now they expect that the development work on the creation of the Promising high-speed helicopter should be completed in about 2020. But postponements are possible, as is often the case with complex and revolutionary developments.
To summarize. Russia has not abandoned high-speed helicopters, although now it is only taking its first steps in this direction. Previously, several similar machines were immediately shown as models of future high-speed helicopters:
- Miles Mi-1X;
- Kamov Ka-92;
- Kamov Ka-90
The first two are multi-purpose helicopters, which, in addition to the rotor (on the Ka-92 it is coaxial), received a pushing screw. It is very similar purely conceptually to the American S-97. With the difference that the latter exists in reality. And flies for a long time.
The most original, we can say - fantastic - version looks Ka-90. For the first time, the helicopter concept model was presented during the HeliRussia 2008 international exhibition, which was held at the Crocus Expo center (other models of high-speed helicopters were shown there). This is a jet helicopter project, which, according to calculations, should develop a speed of 800 km / h, which is absolutely prohibitive for rotorcraft. The concept looks like this: when taking off, the helicopter rises from the ground with the help of hard and shortened propellers. Then he picks up speed of 400 km / h, after which the pilot turns on the turbojet dual-circuit engine, which accelerates the device to 700-800 km / h. The screw, in turn, folds into a case on the "back" of the helicopter.
If you have experienced deja vu now, do not be surprised. A similar apparatus was present in the American science fiction film "6th Day." Perhaps it was from there that those who proposed building the Ka-90 model drew inspiration. Seriously speaking, given the current state of affairs in the economy, it is naive to count on the rapid creation in Russia of a high-speed helicopter (especially such as the Ka-90). In this regard, the example of a long and painful bringing to mind the already mentioned Mi-38, which made its first flight now back in 2003, is very revealing. Recall that the machine still exists only in the form of several prototypes. This is despite the fact that we are facing one of the most priority projects of modern Russian helicopter industry.
If you look more broadly, it should be noted that the concept of a high-speed helicopter, as such, only has to prove its potential by the example of American or European novelties. To challenge the classic rotorcraft, they must be not only fast, but also reliable and economical. And to achieve all this at the same time will be very difficult.