Military Review

Composite blades

Composite blades

Currently, the US military is busy equipping the fleet of its helicopters with carbon fiber composite (carbon) blades, since these new materials have an increased service life, tolerate damage well, they have no problems with corrosion, and they have high reliability.

The extreme military helicopter equipped with composite blades was the Boeing AH-64D Apache Block III. In Fort Irvine, California, Apache Unit III underwent initial operational tests and evaluations, demonstrating new technologies and their capabilities.

One of the key aspects of these capabilities is to increase the flight performance and reliability of the main rotor with carbon fiber blades, however, according to Apache Block III program manager Lieutenant Colonel Daniel Bailey, the use of such materials is unlikely to stop only on the blades. "The blades are the first obvious step," he told the Defense Helicopter.

Structural element
Although such an important flight component as the blades may seem a strange starting point for the introduction of new technologies, it is here in recent years that the US military has honed their skills in composite materials. Bailey points out that these materials will be widely represented on the American military "helicopters of tomorrow": "The next step will be composites in the fuselage, and we are already following this path."

The Apache will also receive a new tail rotor around the next year. Regardless of the Block III process, "our composite tail rotor program continues. This is a parallel Block III program," Bailey explained. "We are in the final qualification stage, but we still have to do a lot of flight tests. Probably, in a year, the Apaches will be equipped such a system. "

New tail blades will also be installed on upgraded models of Block II. This replacement of the traditional main and tail rotor blades is due to the obsolescence of some technologies. These blades, the first use of which is dated 1970-mi years, were no longer completely metal. Helicopters AH-64A and D Block I and II use a composite of metal and fiberglass for the main and tail rotor blades.

In mechanical engineering, it is considered to be a composite material or structure consisting of more than one element. Apache blades are made from exotic alloys in the form of AM 355 stainless steel. Boeing engineers used a variety of multi-tubular AM 355 configurations that were laminated and tied together with fiberglass tubes as an obstacle to the propagation of cracks, which gave the structure sufficient strength to meet military survivability requirements. This complex construction is also expensive.

The current composite blades of the main and tail screws presented in Block III and its parallel program consist of carbon fiber in a polymer matrix, which is what is usually meant when talking about composites.

Improved design
Carbon fibers demonstrate improvements in how they are made and how they function. "By changing the orientation of the fibers and the number of layers and fillers, you can bring the composite blades to levels that were out of reach with metals. In fact, you can make a blade in terms of its twist, its aerodynamic profile or chord function, optimizing its flight characteristics" - explained the chief engineer of the helicopter programs of Boeing John Schibler (John Schibler).

In composite materials of carbon fiber fiber layers are often located alternately to each other at right angles. By correctly choosing the direction of the fibers in these layers, it is possible to achieve the necessary characteristics in specific directions and areas.

"The advantages lie in the strength of the material and in the fact that with equal strength it is possible to provide up to 30% weight loss (compared to metal composites). With the same weight, it provides a much higher rigidity. But usually we are talking about weight reduction," Daniel Kagnatel (Daniele Cagnatel), vice president of modern composite materials GKN Aerospace North America. The company supplies the company Sikorsky with modern carbon fibers for the blades of the main rotor of the Black Hawk helicopter.

In addition to improving rigidity and strength, Schibler also points to economic benefits: "We produce blades at a relatively low purchase price, as well as with low running costs and more profitable maintainability."

Sikorsky manufactures blades for the main and tail rotors using graphite resin spars braided with fiberglass or carbon fiber. Alan Walling, CEO of Sikorsky composite blades, said: "Sikorsky is able to produce fully composite rotor blades in just a third of the time needed to produce metal blades. There is much less chemical waste in the production of composite blades. This is because metal blades require etching in an acid bath to ensure the necessary flight performance of the blades for a long time. "

Improved blades
According to Kagnatel: "The choice of carbon fibers for blades is mandatory. The existing structure of the blades has proven itself in practice, where carbon fiber has improved flight performance compared to metal."

The choice of the Carbon Fiber Apache Unit III rotor blades began with the Affordable Apache Rotor Program (AARP). In 2004, Boeing completed the tests of the blades under the AARP program, proving that the new blades will be cheaper, stronger and, in terms of fatigue life, they can last twice as long as the existing metal blades. Bailey explained that in 2006, the AARP blades were extended by 15 centimeters to improve flight performance, and in 2008, they were tested on Apache, while the blades qualification for Unit III was completed in 2011. .

"The composite rotor blades for the Apache Block III program are currently in production. We manufacture around 20 blades per month and will soon increase their production to 40 and to 60," said Schibler.

In 2013, Block III will be commissioned in the 1st Assault Reconnaissance Battalion of the American Army (1-1 ARB), combat aviation Brigade, 1st Infantry Division based at Fort Riley, Kansas. In May, five Apache Block III helicopters arrived at the 1st strike reconnaissance battalion to train pilots and maintenance services; additional helicopters will arrive in the coming months.

The British army flies on Apache helicopters of model I, but they can be upgraded to the level of Block III. Decision on this is expected in December. If the decision to upgrade to the Block III level is made, then the Apache UK can also receive rotor blades from the British Experimental Rotor Program of the rotor (British Experimental Rotor Program IV, BERPV IV). The BERP IV program was completed in the 2007 year, and composite blades fly over the Royal Air Force EH101 Merlin Mk 3.

Tested and tested
However, this is not the first European military helicopter using carbon blades. The predecessor of Eurocopter, Aérospatiale, claims that this honor fell on an SA 330 Puma helicopter flying from 1970's. Since then, this type is used by many armed forces, including the French army and the US Navy. Composite tail blades are also used on AS532 Cougar, AS565 Panther, NH90 and Tiger helicopters.

The Sikorsky UH-60M Black Hawk uses carbon composite rotor blades from 2008. Of the Sikorsky helicopters, only MH-60R and MH-60S Seahawk have rotor blades from a metal (titanium) spar.

Lieutenant Colonel Billy Jackson, head of the UH-60M Black Hawk retrofit program, said: "We have deployed UH-384M helicopters to 60 troops, Sikorsky has deployed UH-400M helicopters around 60 Some of them have already returned from their second deployment in Afghanistan. "

The army uses broader composite rotor blades, also known as broad chord blades, due to their improved weight characteristics. Weight savings were 204 kilograms. "This was the main reason for creating composite blades, and not creating them simply because they are composite. The main thing is their flight performance," explained Jackson.

“For some time they have been working on the Sikorsky S-92 in a slightly different configuration, thanks to which we already had a good amount of data. There was not a lot of risk in the decision to switch to fully composite blades,” he continued. The Sikorsky firm applied fully composite spars and plating of the main rotor blades on their S-92 helicopters at the end of the 1990-s.

The flight-technical characteristics of the UH-60M helicopters were tested in two deployments in Afghanistan, and Jackson insists that they showed good results: "We are currently busy collecting data on the reliability of the blades. We had damaged blades, as well as repaired and repaired ones. Regarding the question of whether we found cracks in the blades or unforeseen failures due to new composite structures, the answer is no. " Based on current success, the next step could be a fully composite all-rotary stabilizer.

Weight loss plans
In addition to explaining Bailey that the blades were the first step, and the composite fuselage is the following, Jackson said: "We are looking for other applications of composite materials. We are currently developing a fully composite, full-turn stabilizer that will provide a significant weight reduction."

The army began to develop the Black Hawk helicopter's composite tail beam in order to reduce its weight, however, at present, special emphasis is being placed on the creation of a fully composite all-rotary stabilizer including internal components. "We intend to make a fully composite all-turn stabilizer to significantly reduce the weight in the helicopter area, which has the main effect on the center of gravity of the helicopter."

Jackson said that, as already noted in the proposal of the Sikorsky firm, the decision to create a fully composite all-round stabilizer was not due to the desire to improve its flight performance, but only to reduce the cost of its production.

"We still have to do some tests, ballistic and other types of flight tests to make sure that the new product will be just as good or even better than the original one, and then make a financial decision about how we want to implement it on an existing platform, implement him in a promising production or replenish them with a list of existing spare parts. "

The company supplying the composite tail boom, but not the tail rotor blades, is BLR Aerospace from Washington State. Vice President Sales and Marketing Dave Marone (Dave Marone) confirmed to Defense Helicopter that his company was producing a fully composite tail beam for one of the military customers, but did not agree to provide additional information.

Plans for the future
Another helicopter that will have to wait until the 2016 of the year to get the composite rotor blades of carbon fiber is the US Army CH-47 Chinook. "The new composite blades are called Advanced Chinook Rotor Blade (ACRB). The program successfully completed the critical design review (CDR) stage in January 2012 of the year," said CH-47 Chinook retrofit project manager Joe Hoecherl ). Flight and ballistic tests were completed in the 2011 year.

The ACRB program will bring changes in the shape of the blades and their flight performance without affecting their attachment. “These blades will be interchangeable on all Chinook helicopters,” said Hotserl. The large-scale tests in the wind tunnel were completed, which demonstrated that the new blades are capable of providing up to 900 kg of additional vertical thrust, which will allow the helicopter to hang with a full load at an altitude of 1200 meters at an air temperature of 35 ° C.

ACRB blades in a wind tunnel.

The pre-production of blades is scheduled for April 2014 of the year, flight tests for the third quarter of the 2015 of the year, and mass production for the 2016 of the year. In February of this year, it was announced that Boeing is developing composite blades with an increased service life and requiring significantly less time needed to eliminate the incoherence of the rotor blades and balance them. These blades can also be installed on the model of helicopters CH-47D, however, these helicopters are scheduled to be written off by 2019-th year.

Intellectual composites
Most likely, by the 2019 year, carbon fiber blades will require a more sophisticated approach to achieve further improvements in flight performance. Industry agrees that the blades will not consist only of carbon fiber. Kagnatel believes that sensors will be built into them, capable of monitoring the state of the blades and allowing them to more accurately predict their service life.

"Trends are increasingly pointing to embedded systems, elements for heating the front edge of the blade, as well as voltage sensors and deformations of the blades. In the future, such sensors will be an integral part of the blades than their external elements," he said.

However, moving parts can also be mounted on the blades. Paul Weaver, director of research and engineering at the University of Bristol, is working on a project for the UK government. The project is called Intelligent Responsive Composite Structures (IRCS). "The national innovation agency funded the project, which ended two years ago by changing the form of flaps," he told the DH publication.

The national innovation agency is owned by the British government, it is engaged in the financing of research, development and their commercialization. As part of the IRCS program, it was found that the flap-shaped device on the trailing edge of the blade can be used to improve flight performance when moving from a hang to a horizontal flight.

Sikorsky is also engaged in research in this area. It develops active rotor blade technology in conjunction with the US Department of Defense. To date, it is not planned to install these devices on existing blades.

The US military is not a pioneer in the deployment of carbon-fiber blades, but the fact that they are actively equipping their helicopter fleet with new blades confirms that new composites are being actively implemented. For Bailey, the importance of carbon fiber is obvious: "These technologies will stimulate the development of future army helicopters, whether they are new Apache, Black Hawk or Chinook."
Defense Helicopter | July / August 2012 | Volume 31 Number 4
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  1. tronin.maxim
    tronin.maxim 13 July 2012 08: 26
    It is worth recognizing that the Americans have chosen a good direction of development. I think we are engaged in similar studies in Russia, although I have not heard about this anywhere.
    1. beard999
      beard999 13 July 2012 17: 01
      Quote: tronin.maxim
      I think that in Russia we are engaged in similar studies.

      Are engaged. Here is one of the latest news: “Russian Helicopters OJSC is working on a prototype of a promising main rotor blade of a helicopter made of composite materials created using the electronless technology.”
      1. Vashestambid
        Vashestambid 13 July 2012 17: 32
        A modern helicopter is good, it’s bad if it gets whole and intact to enemy hands fellow

        Attention! You do not have permission to view hidden text.
      2. bamboo
        bamboo 13 July 2012 20: 34
        I got ahead))) but I heard already created !!!!!
    2. VAF
      VAF 13 July 2012 21: 23
      Quote: tronin.maxim
      I think we are engaged in similar studies in Russia, although I have not heard about this anywhere.

      Maxim, you amaze me, Rostvertol produces composites as 8 years old and are put on all Mi-35s and 28th and 3 years and the blades come from composite materials the same way as the tail rotors.

  2. Middle-brother
    Middle-brother 13 July 2012 09: 01
    I wonder how much carbon differs from metal in price?

    "Trends are increasingly pointing to embedded systems, blade leading edge heating elements, and blade stress and strain sensors. In the future, such sensors will be part of the blades rather than external elements."

    This is all good, but is it not too difficult? It is known that the more complex the system, the greater the probability of its failure. Although this development is undoubtedly interesting.
    1. Manager
      Manager 13 July 2012 09: 30
      Quote: Middle Brother
      Is it too complicated?

      About 50 - 60 years ago, SUs 27 and 3 7 (for example) also seemed fantastic. Times change. Now everything is possible. Almost all.
  3. dimitriy
    dimitriy 13 July 2012 09: 52
    The author would be interested in domestic helicopter construction. About 10 years ago, Rostvertol developed composite blades. On the MI-28N they are installed, withstand the impact of a 30mm projectile. Perhaps installed on other machines.
    1. Manager
      Manager 13 July 2012 09: 57
      Quote: dimitriy
      composite blades. On MI-28N

      Here is the link
    2. Professor
      13 July 2012 10: 30
      In mechanical engineering, it is considered to be a composite material or structure consisting of more than one element. Apache blades are made from exotic alloys in the form of AM 355 stainless steel. Boeing engineers used a variety of multi-tubular AM 355 configurations that were laminated and tied together with fiberglass tubes as an obstacle to the propagation of cracks, which gave the structure sufficient strength to meet military survivability requirements. This complex construction is also expensive.

      Mi-28 blades fiberglass or fully carbon?
      1. dimitriy
        dimitriy 13 July 2012 10: 43
        I am not an expert, but I think this information is not secret, everything can be found on the Internet. A few years ago, I was (by invitation) at the celebration of the anniversary of Rostvertol and the whole range of helicopters and the new MI-28N were displayed there. Here they told me a little about his blades without going into details.
      2. Pimply
        Pimply 13 July 2012 13: 30

        Here in the last pics - a photo story about production.
        1. Professor
          13 July 2012 17: 49
          Composite - yes, carbon - no. The photo clearly shows the fiberglass winding.
      3. VAF
        VAF 13 July 2012 21: 24
        Quote: Professor
        Mi-28 blades fiberglass or fully carbon?

        Fiberglass! +!
  4. B_KypTke
    B_KypTke 13 July 2012 09: 56
    Considering the undeniable leadership of Russia in the development of composite materials, TsAGI will not create a big problem for composites. That is to introduce into production, put into series, to achieve a stable quality of manufacturing - this is the challenge for the future.
    1. Professor
      13 July 2012 10: 24
      Given the undeniable leadership of Russia in the development of composite materials

      I could not resist ... laughing
      Not just leadership, but also "undeniable" ...
      Please give examples of mass production of carbon parts in Russia. After all, this will not amount to work, since "world leadership" is all the same. wink
      1. sapulid
        sapulid 13 July 2012 14: 48
        For example, carbon fairings rockets. On the defense, the cabon, unfortunately, is more applicable ...
        1. Professor
          13 July 2012 17: 46
          Carbon rocket fairings? Since when has carbon become heat resistant?
          1. luiswoo
            luiswoo 14 July 2012 07: 37
            Quote: Professor
            Carbon rocket fairings?

            Suddenly yes. Angara will have one. And for the "descent vehicles" delivered by ICBMs, so as not to watch their body burn with a blue flame when entering the dense layers of the atmosphere, they came up with such a thing as thermal protection. Google the Union, Buran and all sorts of Endeavors there.
            Since when has carbon become heat resistant?

            Why such a thick trololo? Up to 2500 ° C, the operating temperature in an inert environment is still based on graphite. Heat-resistant steel with its 900-1000 ° C, did not roll around.
            1. postman
              postman 20 July 2012 18: 48
              Quote: luiswoo
              Angara will have one.

              Why do you think so? Which of the "Hangars"? 1.2, A3, A5, A7 - ????
              The fairing, as a rule, is the characteristic of the upper stage or mon (for "civilian launch vehicles)

              Quote: luiswoo
              Up to 2500 ° C, the working temperature in an inert environment is still based on graphite.

              You write nonsense:
              1. carbonation up to 1500 ° C (in inert)
              2. thermometer up to 2700 ° C,(in inert)
              ALL THIS IN AN INERTAIN ENVIRONMENT, which is not related to the physical ...

              The melting point of graphite is 3600 C
              however, its intense evaporation starts at 2800 ° C!

              And the performance of oligomers (epoxies) is even worse.
              1. luiswoo
                luiswoo 20 July 2012 21: 05
                Quote: Postman
                Why do you think so? Which of the "Hangars"? 1.2, A3, A5, A7 - ????
                The fairing, as a rule, is the characteristic of the upper stage or mon (for "civilian launch vehicles)

                Dear, I understood what I wrote? Does the head fairing tell you anything? If not, google.
                ALL THIS IN AN INERTAIN ENVIRONMENT, which is not related to the physical ...

                Physical .. what? Start education with electric vacuum devices, when you understand that an inert medium is achievable not only in electric bulbs, then you may remember that heat resistance was meant in special conditions, no more.
                1. luiswoo
                  luiswoo 20 July 2012 21: 21
                  In the Proton-M and Angara launch vehicles, the entire warhead, all the upper compartments are completely made of carbon fiber, ”the Commissioner emphasized. According to him, composite shells play the role of acoustic protection for the payload, because when launching a rocket there is a very powerful acoustic impact of the order of 100 dB, and the spacecraft is very fragile.
                  “So, when using aluminum and fiberglass head fairings in the shells, for acoustic protection of the apparatus, mats with a thickness of half a meter are hung inside, which increase the weight and reduce the space for the payload,” the Commissioner explained. “And that's not very good.”
                  Oleg Komissar said that the State Space Research and Production Center. Khrunicheva, together with ONPP Technologiya, is working on new fairings for heavy-duty launch vehicles of increased diameters. “This is a promising direction of our development, I think, in a year or two we will move to larger ones,” the Commissioner emphasized.

         - сайт производителя.
                  1. postman
                    postman 21 July 2012 00: 35
                    Cunning Komisar
                    GO is made of several shells, which are three-layer structures with aluminum honeycomb core and carbon fiber lining (!)

                    Development of the Institute ONPP "Technology":

                    Oversized, integrated, dimensionally stable structures made of polymer composite materials for the Proton-M and Angara launch vehicles, the Spektr-R, Spektr-UV, Ramos, Condor, NetLander and other spacecraft
                    The professor writes correctly: do not confuse the composer and carbon.
                    Wood chipboard (particle board) or fiberboard (fiberboard) is the same composite, and OSB PLATE is generally a polymer composite ...
                    1. luiswoo
                      luiswoo 21 July 2012 01: 43
                      Quote: Postman
                      The professor writes correctly: do not confuse the composer and carbon.

                      No, it’s wrong, carbon fiber is also a composite material (carbon fiber + impregnation), like fiberglass (fiberglass + impregnation), the first is only more difficult to manufacture.
                      Quote: Postman
                      Cunning Komisar
                      GO is made of several shells, which are three-layer structures with aluminum honeycomb core and carbon fiber lining (!)

                      Where is he cunning? He kind of says how good it is when carbon fiber reinforced plastic and how not so good when fiberglass and aluminum - you have to install additional acoustic protection. The construction of carbon fiber parts, I suspect, is known to him.
                2. postman
                  postman 21 July 2012 00: 14
                  luiswooDear, did you understand what you wrote? Does the head fairing tell you anything? If not, google. ,
                  1. Understood, and therefore wrote. And YOU (rude): read what is written?
                  2. The head fairing is familiar, although my specialty is
                  3. The physical medium is simpler than air, where the movement of the "head fairings" takes place, but by no means Inside the devices.
                  Your thought, after "remember" - is incomprehensible, at all.
                  4. I gave the temperature readings. Moreover, you pulled out parts "all over the world" and have no idea about:
                  PAN-fiber, oxidation, carbonization, graphitization. Yes and prepreg you hardly know.
                  If you are not in the know, then I will explain the "task" of carbon not heat resistance, but strength, with the ability to simulate strength in a given direction.
                  You are confused with silicates and ceramics.
                  1. luiswoo
                    luiswoo 21 July 2012 02: 15
                    Quote: sapulid
                    For example, carbon fairings rockets. On the defense, the cabon, unfortunately, is more applicable ...

                    Quote: Professor
                    Carbon rocket fairings? Since when has carbon become heat resistant?

                    I don’t understand what the argument is about? It seems that they found out that for the head part of the ICBM, its carbon body does not need to be heat-resistant - there is heat protection for this. What carbonic GOs do for civilian launch vehicles, and for obvious reasons, that they don’t need to return from orbit, and therefore they don’t need to be heat resistant. What is carbon (most likely one carbon fiber) in special conditions can be heat resistant. What are you trying to prove to me?
          2. sapulid
            sapulid 9 August 2012 06: 38
            Not a rocketeer, I repent. Apparently reflectors. I watched a film on the manufacture of Russian missiles, which talked about the use of carbon for the manufacture of surfaces of warheads. It's been a while, however. If you messed up, my apologies.
      2. MI-AS-72
        MI-AS-72 13 July 2012 20: 54
        Professor do not be silly You do not go blades made of composites "fly" in the USSR since the mid-70s on the KA-25. In the USA, to this day, military vehicles have standard blades, the reason is the price, on our helicopters for the same reason, the high production price and of course sales does not allow composite blades to be massively used, there are options for composite blades for MI-38, Mi-8MTV (AMT ) blades RV, about the Mi-28 and Mi-2, KA-226, etc. We have already written here. In the late 90's, Milevtsy developed blades for Sikorsky. Further too lazy to write, but believe me there were times when we were ahead of the rest.
        In European countries, blades of composites began to be used a little later than ours and in light helicopters. We had a project of all-inclusive composite materials for MI-26, this is the level. Maybe in a year and it will be realized.
        1. Professor
          14 July 2012 10: 18
          Let's not confuse just composite blades with carbon blades and then everything will fall into place.
          1. postman
            postman 21 July 2012 00: 41
            Was there in the article about the solution to the problem of "point" impact perpendicular to the blade surface (crumb, dust, sand).
            Do not turn into a sieve after a certain period of operation?
            1. Professor
              21 July 2012 10: 32
              It was not specifically about this, but it was noted that the blades are more durable under all operating conditions.
  5. Kostyanich
    Kostyanich 13 July 2012 12: 33
    well done amers evolve you will achieve something
    but for some reason they prefer to buy the good old MI
    1. ra1647
      ra1647 13 July 2012 12: 46
      MI, in my opinion, they buy only for Afghanistan, to them I think our turntables are not why ????
  6. Oleg 11111
    Oleg 11111 13 July 2012 15: 44
    Rotor blades

    In addition to helicopters, OJSC “Rostvertol" produces rotor blades for helicopters such as Mi-24 (-35), Mi-28, Mi-26, Mi-2.
    Main rotor blades for Mi-28N and Mi-35M helicopters:

    The rotor blade is made using composite materials and consists of a spar, tail compartments and an electrothermal de-icing system.

    The main power element of the blade structure is the spar, which forms the nose of the blade.

    It is made by spiral winding unidirectional glass tape on a binder. The tail compartments of the blade consists of a polymer-plastic aggregate aggregate, organite sheaths glued to it.

    In January, 2012, the OJSC Moscow Helicopter Plant M. L. Mila ”began assembling the first prototype of a modernized medium transport helicopter Mi-171А2. The distinctive features of the Mi-171А2 are the new turboshaft engines VK-2500PS-03, the SAT "Safir" 5K / G, the composite blades of the main and X-shaped tail rotor, as well as the modern complex of on-board equipment of the CCD-17 and a significant increase in the assigned and turnaround machine resources and its basic systems. The payload mass inside the cab is 4000 kilograms, on an external sling it is up to 5000 kilograms, the maximum speed reaches 280 km / h, and cruising speed is 260 km / h.
    Read more:
  7. Oleg 11111
    Oleg 11111 13 July 2012 16: 38

    Composite Helicopter Propeller Blades

    Currently, blades made of composite materials are widely used. They have the following advantages: the ability to create and accurately withstand during manufacture the optimal shape of the profile of the blade; significantly greater resource and reliability due to the greater specific strength of the material and insensitivity to stress concentrators; slow and limited propagation of fatigue cracks; high corrosion resistance; internal damping, useful for absorbing vibrational energy; high manufacturability and less laborious manufacturing.

    Such blades are mounted on Ka-25K, Ka-26 and other helicopters. The main power element of the blade is a spar made of fiberglass. It has the shape of the bow of the blade. In the butt part of the spar is a steel node for attaching the blade to the sleeve. It is attached to the spar with bolts and glue. For static blade balancing, the spar has an end and butt balancing chambers. In the bow of the spar, protected from abrasion by a light-resistant rubber coating, there is a centering load poured in brass forging.

    Tail sections are glued to the rear of the side member, which consists of thin fiberglass sheathing and lightweight aggregate glued together. For dynamic adjustment of the carrier system, there is a metal trimmer. The blade is equipped with an alcohol de-icing system.

    For the timely detection of fatigue cracks in the side members of the blade, the blades are equipped with signaling devices for damage to the side member. This ensures the operational reliability of the blades. For all-metal blades, the system consists of plugs at the ends of the spar, ensuring the tightness of its internal cavity, and an indicator of damage to the spar. The alarm includes a red signal cap connected to a helium-filled bellows and a charging valve.

    Outside the detector is covered with a transparent plexiglass cap. The inner cavity of the spar is filled with air under pressure. Air compresses the bellows and draws the red cap into the housing. In the event of a crack in the spar, the pressure in it drops and equalizes with atmospheric pressure. Under the influence of internal pressure, the bellows opens and pushes out the red cap, which signals damage to the spar.

    The fiberglass blade system alarm system has some peculiarity. The outer surface of the spar tube is lined with glass tape, therefore, if a crack occurs in the spar, air from its internal cavity cannot be blown off. In this regard, in the manufacture of the blades, double fluoroplastic cords are laid along the spar pipe, wrapped with raw glass tape, and the pipe is polymerized in the mold. Then the cords are pulled, and channels are formed into which air is blown off in case of damage to the spar.
  8. alex86
    alex86 13 July 2012 22: 55
    But who is literate, at one time, American helicopter pilots praised Cobra for the strength of the screws, they say they are not afraid of thin branches (cuts with a screw) and you can sit in small forest glades. Being a complete amateur, I can, however, note that indeed, on the American chronicle, the distance from boarding helicopters to trees is visually less than on our chronicle. Can someone comment?
    1. alex86
      alex86 16 July 2012 18: 41
      There are no literate ... sad
  9. warrior
    warrior 14 July 2012 08: 37
    I did not understand that the novelty itself. Composite parts on serial aircraft have coexisted since the late 70s.
    If it’s about corbon, then now carbonomania is everywhere. Particularly liked composite carbon steel trunks. Who cares here
  10. OlegVK
    OlegVK 6 January 2014 12: 41
    Dear Sirs, Readers and Writers.
    The term "carbon fiber" blades is applicable only to the components of radio-controlled models and even then to a lesser extent. The main advantageous characteristics of this material - its high rigidity and relatively low weight - are also the main obstacles to its use in helicopter blades. Firstly, the blade designed for each aircraft must have a strictly defined mass, i.e. should not be lighter than some of the calculated values, otherwise the blade will have too much swing motion. Fiberglass-based materials are perfect for this. Secondly, carbon plastics are extremely fragile with concentrated and even very insignificant impacts, literally crumbling into dust. Mowing branches when planting in the forest or landing on gravel sites will definitely not work. Therefore, for the production of blades, more and more complex combinations of fibers and fabrics are used, including more organoplastics (the Western developer designated it as Kevlar) with better characteristics in terms of impact perception. And the carbon fiber in the blades is used in very small quantities as an integral part of the reinforcing elements - mainly stringers. At the same time, the developer tries to electrically insulate the fibers as much as possible when approaching the surface of the product. On experimental blades with a high carbon fiber content, there were cases of blade destruction when exposed to a strong electrical discharge (lightning).
  11. Gonoriy
    Gonoriy April 28 2015 13: 39
    The issue of using composites for blades has already been resolved. All that remains is to completely replace the metal blades on already flying machines.