The CV / MV-22B tiltrotor was adopted by the US Marine Corps in 2007. This is the only aircraft currently in operation that takes off and lands vertically and has a high horizontal flight speed.
Helicopters, since their introduction in the French Army and Air Force during the 1954-1962 war with Algeria, have added a new dimension to the concept of military operations
The use of helicopters to support vertical maneuver allows combat units to be delivered, regardless of geographic obstacles, to the place where the opponent can least expect. This opens up new opportunities for warfare. Since the Algerian conflict, technological advances and continuous improvements in the design of the helicopter have increased its capabilities, in particular, payload and lift. However, the maximum speed and range of modern medium and heavy multipurpose helicopters, apparently, have reached their upper limits.
For example, Boeing's latest model F of the CH-47 Chinook family of multipurpose transport helicopters has a top speed of 315 km / h and a range of 370 km. The CH-47F is followed by the Russian Mi-35M helicopter with a maximum speed of 310 km / h and a range of 460 km. The medium AW-101 helicopter from AgustaWestland / Finmeccanica has a maximum speed of 309 km / h, while the new generation AW-139M medium helicopter of the same company has a maximum speed of 306 km / h. As you can see from this list of maximum speeds, not all modern helicopters can reach a maximum speed of just over 300 km / h.
Cruising speed is important because it affects the "turnaround" of the aircraft when performing a combat mission. The faster the helicopter flies, the sooner it will reach its target and the sooner it will be able to return to pick up and deliver additional forces and supplies. A rapid build-up of ground forces is essential to the success of an airborne assault. Thus, the ability of an aircraft to fly more departures over a given time period is extremely useful. Flying at high speed also increases survivability by reducing the time the aircraft is exposed to enemy observers and gunners on the ground.
Increased range is also desirable, although it is mainly related to fuel availability. In the past, special attention has been paid to increasing the range, which is directly related to the capacity of the fuel tanks. Medium and heavy helicopters, such as the Mi-26 with a range of 800 km and the Sikorsky CH-53E with a range of 999 km, need exactly this range to perform several sorties without refueling. Meanwhile, refueling rods mounted on aircraft such as the CH-53E helicopter or the MH-60G / U Blackhawk special operations helicopter allow long-range missions to be carried out deep behind enemy lines. However, the range and cruising speed are closely related from the point of view of practical operational meaning. Although the aircraft may have a range that allows hundreds of nautical miles to reach the landing area, it is necessary to take into account the return flight and the time spent on it, as this may lead to an increase in the time of the landing force build-up. In this case, it will be unable to quickly perform tasks such as "round trip" due to the increased flight time. That is, in order to use the long range most effectively, the aircraft must again fly faster.
Swivel screws
Despite initial difficulties and criticism from skeptics, the Bell-Boeing CV / MV-22B Osprey tiltrotor, which began life in 1981 as part of the Vertical Take-Off / Landing Experimental (JVX) joint project, changed the concept of vertical lift operations. First deployed by the US Marine Corps in 2007 and the US Air Force Special Forces in 2009, this tiltrotor is currently being used not only in combat (interventions in Iraq and Afghanistan), but also in humanitarian and disaster relief missions such as he provided relief after Typhoon Haiyart that devastated parts of the Philippines in 2013. The Marines, in particular, saw in the MV-22B tiltrotor a solution to the problem of delivering troops from ships far beyond the horizon. This mission was previously performed by the heavy transport helicopter CH-46E Sea Knight, but the flight time was unacceptable. This helicopter took quite a long time to build up the necessary contingent of landing forces, while it made several sorties, the limited number of troops remained vulnerable.
The unique characteristics and capabilities of the MV-22B tiltrotor are aimed at solving such problems. It can take off vertically from amphibious assault ships, but when switching to level flight and turning the engines down, it can fly at a speed of 500 km / h. This is more than double the speed of the CH-46E, which means more than half the flight time to the same landing zone. Plus a long flight range of 722 km and a higher payload in the cockpit of 9070 kg and on a suspension of 6800 kg further increase its efficiency. The practical experience gained with the MV-22B has increased interest in tiltrotors as a type of aircraft and improved the prospects for the next generation tiltrotor. This is especially true given that the CV / MV-22B, in fact, uses technologies, materials and processes for development and manufacturing of the 70s of the last century, which, without any doubt, have advanced significantly over the past three decades.
Bell-Boeing builds on the CV / MV-22B experience in developing the promising V-280 Valor tiltrotor aircraft and incorporates the latest technologies, materials and manufacturing processes to create a more advanced tiltrotor aircraft.
For the Sikorsky S-97 helicopter, a scheme with two counter-rotating main rotors and a tail pusher rotor was used. This made it possible not only to get high speeds, but also the ability to fly sideways and even back.
Promising developments
As noted above, the aviation industry is working to overcome the maximum speed limit for helicopters. The problem of increasing speed is partly related to the very element that allows the helicopter to fly vertically - the upper rotors. The problems that needed to be solved were related to the aerodynamic drag of the propellers and the body, the elimination of air blowout from the blades, reverse airflow and air compressibility. A discussion of the technical subtleties of these problems could take several pages, but one thing is clear - they must be solved in one way or another in order to change the dynamics of the helicopter flight. Designers try to solve these problems by going in various directions and "grope" there for answers.
For example, Bell Helicopter took the proven CV / MV-22B rotary propeller concept and adapted it for their V280 Valor tiltrotor project. According to Steve Matia, Director of Business Development for Advanced Rotary Propeller Systems: "The design and manufacture of the V-280 is based on the experience gained and tested on the CV / MV-22B tiltrotor, while applying the most advanced design and development technologies." As he explained, one of the most interesting solutions is implemented in the V-280 nacelle. The CV / MV-22B tiltrotor turns the entire nacelle. On the new V-280, only the propellers and gears rotate, while the nacelle and engine remain stationary. This allows for safe embarkation and disembarkation, since the engine housing does not interfere with the landing, and also reduces maintenance requirements. The V-280 tiltrotor, designed for various tasks, is smaller than the CV / MV-22B tiltrotor. It will have a cruising speed of 520 km / h, a combat range of over 930 km, it will be able to hover at an altitude of 1828 meters and fly at a temperature of 32 degrees Celsius with a full combat load, while surpassing existing helicopters in maneuverability. Together with Lockheed-Martin, Bell offers the V-280 tiltrotor for the FVL JMR-TD (Future Vertical Lift Joint Multi-Role Technology Demonstration) helicopter program. The companies have scheduled the first flight of their V-280 tiltrotor for August 2017.
The S-97 is already noticeably quieter than traditional helicopters due to the use of a pusher tail rotor and twin beam tail fins. When there is no need for high speed, but low visibility is needed, the push propeller makes it almost silent
Airbus Helicopters' promising X3 helicopter has short wings that generate lift at speeds in excess of 80 knots, and two turboprop engines for forward flight. Pilots speak favorably about the maneuverability of Airbus Helicopter's aircraft
X2
Meanwhile, Sikorsky and Boeing have teamed up on the FVL JMR-TD program to offer the SB-1 Defiant helicopter. They propose to take the Sikorsky X2 project with counter-rotating coaxial propellers and a pushing propeller as the basis for a new aircraft weighing no more than 13636 kg. There are advantages to this Sikorsky-Boeing approach, as the 2,720 kg X2 Technology Demonstrator flew several test flights in 2010, in which it reached a record speed of 463 km / h. In 2015, Sikorsky presented its prototype of the S-97 Raider, a light tactical multipurpose helicopter weighing about 5000 kg.
Sikorsky and Boeing SB-1 Defiant helicopter project
Chris Van Buyten, VP of Innovation Projects at Sikorsky, who leads the project: “Flying further and faster in a coaxial helicopter is definitely a key requirement. However, with our S-97 project, we want to showcase the next generation rotorcraft that can outperform traditional helicopters in every performance parameter, especially at low speeds and when hovering. The secret of the X2 coaxial is that the counter-rotating main propellers provide lift and forward flight without a tail rotor. Above 150 knots (277.8 km / h), thrust is provided by the push propeller, so the main propellers do what they do best - provide lift.” Van Buyten went on to speculate that the S-97 and SB-1 aircraft "will radically change the way military pilots now fly and fight in helicopters." By the time the Sikorsky and Boeing team take their SB-1 into the air in 2017, Sikorsky will have its third experimental X2 in less than 10 years, which could finally confirm the project's inherent scalability to the size of the UH medium multipurpose helicopter. -60 Black Hawk.
Sikorsky's X2 project
The goal of the FVL JMR-TD program is to develop and deploy an aircraft with significantly improved performance and capabilities, which is capable of performing a wide range of tasks, ranging from reconnaissance and attack to the transport of troops and cargo.
Hybrid projects
Airbus Helicopters (formerly Eurocopter) is taking a hybrid approach to developing future-proof helicopters, using some of the essential elements of traditional aircraft, such as short rectangular wings. Such a solution allowed to significantly increase flight speeds, which was demonstrated in 2012 by a test flight of the X3 technology demonstrator, which reached a speed of 255 knots (472 km / h) (above the X2 speed record). The X3 project combines an upper rotor for lifting and hovering and short wings with turboprop engines installed on them, providing thrust for forward movement (which is why the term "hybrid" is used here). It does not have a rear rotor, but instead has a horizontal stabilizer with vertical tail stabilizers at each end. Flying forward at speeds in excess of 80 knots (148 km / h), the wings begin to generate additional lift and at high speed provide almost all of the lift for this aircraft.
Airbus has not yet disclosed its plans for a new military aircraft using the approach demonstrated by the X3 project. However, a company spokesman suggested that many of the current helicopters could include these design solutions. Since the X3 project is based on the deeply modernized body of the light universal AS-365N3 Dauphin helicopter from Airbus Helicopters, this seems quite possible. The X3 was shown to the US military but ultimately did not make it to the FVL JMR-TD program. Airbus has indicated its intention to focus on search and rescue missions and is continuing to work on an aircraft based on the X3 project that could take off in 2019.
RACHEL
Russian Helicopters announced in 2009 that it is developing a promising high-speed aerodynamic helicopter with retractable landing gear and a patented implementation of the SLES (Stall Local Elimination System) system in the main rotor design. According to the company, the Mi-X1 will have a cruising speed of 475 km / h and a top speed of up to 520 km / h. In August 2015, at the MAKS air show in Moscow, the V. I. Mil showed a demonstration of the RACHEL (Russian Advanced Commercial Helicopter) advertised as a high-speed helicopter. The helicopter can take on board up to 24 passengers or 2.5 tons of cargo and transport it at a maximum speed of 500 km / h to a maximum distance of 900 km. The holding said that test flights will begin in December, and mass production in 2022. In December 2015, a deeply modernized Mi-24K with new curved rotor blades was presented to the public. The aim of this development is to reduce aerodynamic drag, increase the stability and speed of the helicopter flight. The company expects that the maximum speed of the experimental aircraft will increase from 333 km / h to 400 km / h. According to the company, if it is possible to re-equip another aircraft with curved blades, this will increase the speed by 30 percent.
Russian project of a promising high-speed helicopter RACHEL
X-PLANE
A small American company AMV is developing its own project of a high-speed vertical take-off vessel with propellers located on its short wings. Prototypes clearly hint at a combination of a VTOL (Vertical Take-Off and Landing) vehicle and a high-speed helicopter. AMV has launched its X-PLANE demo and expects its AMV-211 to achieve a top speed of 483 km / h, a cruising speed of 402 km / h and a range of 1110 km. Although the company submitted its proposal for the FVL JMR-TD program, its project was not selected, and the X-PLANE project was not stopped and its development continues.
AMV's X-PLANE concept
Controlled traction
Another candidate in the high-speed helicopter industry uses Piasecki Aircraft's patented Vectored Thrust Ducted Propeller (VTDP) design in combination with main wings. An experimental twin-engine four-bladed X-49 Speed Hawk took off for the first time in 2007 and reached a speed of 268 km / h. This model was based on the hull of the Sikorsky SH-60F Seahawk deck-based anti-submarine helicopter. The work was originally funded by the US Navy and then by the US Army to demonstrate ways to increase the speed of existing helicopters to 360 km / h. This project was not selected for the FVL JMR-TD program.
Piasecki Aircraft project based on Sikorsky SH-60F Seahawk deck anti-submarine helicopter
The SB-1 is a further development of the Sikorsky S-97 project and is another candidate for the FVL JMR-TD program, which aims to meet the need for a medium multipurpose helicopter.
Reason prevails
The militaries of several countries, including the military forces of the United States and NATO, will face the problem of aging of their helicopter fleets in the coming decade. Many of today's helicopters were put into service in the 1980s, and their service life is already approaching 30 years. For example, the AH-64 Apache combat helicopters produced by McDonnell Douglas / Boeing began to be supplied to the troops in 1986 and, despite a number of improvements, have essentially the same flight characteristics. The UH-60 family is even older, the first helicopters were delivered in 1974. The newest UH-60M helicopters have fly-by-wire control systems, a common architecture, a new powerful and reliable engine, but the speed remains the same. The first task of the FVL JMR-TD program will most likely be the replacement of the UH-60 series helicopters, which explains the similarity of the designs of the cabins offered for it.
So, military operators inevitably seek to replace their aircraft. And here they are faced with the question of whether to keep the proven designs, albeit with the inclusion of digital electronics and avionics, fly-by-wire systems and composite materials, or to move towards projects that offer a new level of opportunity. The second question is the possibility of developing a universal vessel that could perform a variety of tasks. The US military initially wanted a maximum of three aircraft to carry out all its intended missions. This idea has changed several times, and so far they have settled on three projects: the Light Scout light helicopter (operation since 2030), the Medium-Light medium, the universal / attack helicopter with the start of operation since 2028 and, finally, the Heavy Cargo transport with the beginning of operation from 2035. In addition, the US Army is counting on the implementation of the "Ultra" project, which is scheduled to begin operation in 2025. It is a new vertical take-off cargo vehicle with characteristics similar to those of transport aircraft powered by turboprop engines such as the Lockheed Martin C-130J or Airbus A400M. But, judging by the results of the briefing by the Deputy Director of the Department of Ground Combat and Tactical Combat Systems Jose Gonzales, held at the US Department of Defense in January 2016, everything seems to be changing again. A categorization is suggested based on capabilities needed rather than weight. These new categories have not yet been announced.
Even without the Ultra option, this concept of new aircraft not only has technical problems, but can also affect the current position of the US Air Force - with its ambition and deadlines. Probably, from an operational point of view, in various tasks, some projects may be preferable to others. The main issue remains the proportionate financing of such a program and how it can affect other modernization projects of the army.
Fly forward
The operating experience of the CV / MV-22B tiltrotor reveals the advantages of this aircraft and indicates new ways to use its unique capabilities. Based on this experience, the US command of the special operations forces USSOCOM has already expressed an interest in increasing the number of CV / MV-22B tiltrotors over the initial requirements. Sufficient experience of the X3 project in the framework of the FVL JMR-TD program shows the reality of achieving high speed, increased maneuverability and greater flight range. Currently, there is a question of determining the viability, expandability and adaptability of high-speed helicopters, as well as their cost, which will allow them to perform the entire range of combat missions. High-speed helicopters are on the horizon, but how soon and in what form is still unknown.
