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Yakovlev Yak-24 (NATO Horse)

The Yak-24 tandem rotor helicopter (Horse) is credited to A. Yakovlev, the noted fixed-wing designer. The rotor systems appear to be two units as used on the MI-4. It is also possible that the main transmissions are essentially those of the Mi-4. The gross weight of the craft is approximately 30,000 Ibs. Two engines are used with a total rating of about 2,000 hp. The normal crew of four includes two pilots, a navigator, and a radio operator. A maximum payload of four tons was reported. When at the end of 1951. the development of heavy transport helicopter Yakovlev Yak-24 design bureau was started did not have much experience in the creation of helicopters; After lengthy ground tests, 3 July 1952., the fourth prototype was able to make a flight on a leash. In April of 1955 it started production and produced at least 100 such helicopters.

In September 1951, Stalin summoned to the Kremlin the main Soviet aircraft manufacturers asking them to develop, within one year, two large helicopters with a payload of 1200 kg and 2400 kg. OKB-329 and Mikhail Mil OKB-115 Aleksandr Yakovlev went to work: the first would give birth to the Mil Mi-4, while the latter ventured into a concept with two lifting rotors in tandem, the Yak-24. For faster work, Igor A. Erlikh (at the head of the helicopter division of the OKB-115) decided to use the rotor and engine developed by OKB-329 for the Mil Mi-4, namely Chvetsov ACh-82V 1700 hp and four-bladed rotor 21m in diameter. The Yak-24 helicopter was designed in a very short period of time: from the beginning of the conceptual design (October 1951) before the first flight (July 1952) it took only nine months. Designing a comparable duty helicopters Piasecki H-16 began in 1946, and the first time it took off was only in 1953. But the Piasecki helicopters served as a catalyst for the emergence of a longitudinal scheme large transport helicopter in the Soviet Union.

The Chief Designer of the Yak-24 was Igor Erlikh. After graduating with honors from the Moscow Aviation Institute in 1947, IA Ehrlich began to work in the General (later General) Designer Design Bureau AS Yakovlev as an engineer estimator and aircraft engaged in dynamic strength. At this time the CB formed a group that created a coaxial helicopter with engines M-11, which has received index SH - the main designer ["ideologist"] of this group was LS Vildgrube.

In February 1948 they began to establish the Yak-100 helicopter. National helicopter veteran PD Samsonov who led the project drew Ehrlich to work as an engineer, then leading designer of the machine. It was here that a young specialist gained experience design, test and development work. The experimental Yak-100 helicopter had a single-rotor scheme with tail rotor and air-cooled engine AI-26GRFL. In the second half of 1950 it passed the state tests with a positive assessment. However, serial production was not adopted because the competition was won by the Mi-1, which showed the best flight data.

Development of unique at the time helicopter with longitudinal scheme began September 24, 1951 by a group of GI Ogarkov, SA Bemowo, LM Schechter and IA Ehrlich, led by NK Skrizhinskogo and PD Samsonov. The Government decision on the construction of advanced helicopters in Leningrad and Saratov serial was made in ten days - on 5 October. Simultaneously with the Yak-24 in the same Decree created the Mi-4. And the Ministry of Aviation Industry [MAPE] considered it appropriate that the basic units of these helicopters - rotors, rotor gearboxes, engines, warping machines, control system, boosters and mechanical components have been or are interchangeable or identical.

The design was based on broad cooperation with the involvement of research institutes - TsAGI, CIAM, VIAM, NIAT, INSS, LII and experimental design bureau, in particular, the main designers Shvetsova, Basta Toropova, Kupreyanova, Fedoseyev and others. The definition of basic units and their arrangement on both helicopter design bureaus worked together. During the execution of the working drawings bushings, swash plate and blades for the Yak-24 took ML experts Mile. Excellent coordination allowed carrying out design work in a very short period of time. For December 10, 1951, chaired by Commission prototyping Marshal N.S.Skripko were reviewed and approved the layout and conceptual design of the helicopter Yak-24 - the machine again, by the time the new unique longitudinal scheme, and on-duty and the expected flight characteristics.

In parallel with the design and construction of helicopters in TsAGI was conducted a large research project on the creation of calculation methods of performance, manageability, sustainability in building and testing models and screw devices. Since January 1952 the center of gravity of work on the production of advanced helicopters moved to Leningrad, where IA Ehrlich was sent on January 3. In Leningrad the building of prototypes demanded the release of a large number of drawings, which can be done only with the direct production of machines - right in the shop were plywood boards on which to draw, how and what to change. In addition, it was necessary to 'build a powerful slipway for static tests of the helicopter.

With the participation of the young leading engineer (in Leningrad Ehrlich celebrated his 30th birthday) was actually the first five months of hard work in the factory # 272 MAP produced slipway and conducted static tests of the prototype, built two helicopters: # 0,127,231 - byo May 2 and #01272302 - by June 1st. They prepared a significant number of drawings. Notable were BA Sigaev - later chief engineer of the plant, PK Havronichev - Chief Technologist, BC Metlenko - head of the assembly shop, Nina Tretyakova - welder. The significant contribution made staff-standard design of the plant department, headed by MN Khanin.

Noting the great work the manufacturers and developers of engines, gearboxes and other components for helicopter units, it is necessary to bear in mind that the engine is a modification of well-mastered in the production and operation of the serial DB-82. Both helicopters were brought to Moscow by train. Transportation of the finished helicopter carried on three platforms, and it was mounted on one, and two outer covered the nose and tail. The helicopter only dismantled the rear gear unit with a frame, rotor blades and the loading bridge. The creation of Yak-24 helicopters and Mi-4 in terms of all-time was a serious challenge for the entire aviation industry and the test of its organizational and technical maturity. Moscow helicopters were toured by the marshals AM Vasilevsky and V.D.Sokolovsky, Air Chief Marshal P.F.Zhigarev, P.V.Dementev Minister and other high officials.

The first test flight of the prototype of the Yak-24 took place on July 3, 1952 after 9 pm (the afternoon was a breeze). Flight lasted less than ten minutes by SG Brovtsev (who later received the title of Hero of the Soviet Union). In the cockpit with him was mechanic PS Semin. After each revision carried out dozens of approach and hover for 5-10 minutes. Finally, everything was ready for a real departure. The historic event took place July 3, 1952, when the crew of Brovtsev Milyuticheva and first performed at the Yak-24, long flight. It was an undoubted success of the Soviet helicopters - the Yak-24 was the first Soviet twin-screw helicopter with the longitudinal scheme. Moreover, engine power and payload was superior to all the foreign machine.

However, after the joy came and serious problems. After the first and subsequent flights the pilots noticed the increased vibration, and in some modes, a significant vertical shaking. As a result of vibration to detect defects associated with the design strength - cracks and destruction of individual components. It began painstaking work to eliminate this evi. Domestic experience on shaking was not resolved, but the designers know very well how vainly others had struggled with high vibrations in helicopters transverse schemes abroad: Americans on Piaseckis, and the British on the Bristol Type 173. One way to solve the problem was a proposal to change the vibration characteristics of the blades, shortening them by 50 centimeters. Soon (in two weeks) shorter blades installed in the helicopter and carried out a test flight. pilots report all pleased - shaking was gone. The absence of vibration was then confirmed by a large number of flights and records of equipment, and hence it became possible to carry out production tests to determine the basic characteristics of the helicopter.

Officially, the factory flight tests were completed November 15, 1952 Two helicopters completed 141 flight, the incident 36 hours 06 min. Almost half of the flights (63 flight lasting 14 hours 48 minutes) has been associated with the study of vibrations. The report on factory flight tests recorded: "Flight of the helicopter characteristics generally correspond to specify according to the decision of the USSR # 3821-1749ss on October 5, 1951"

Failures gave rise to mistrust of the aircraft by the state commission. Helicopter repeatedly returned for revision and re-production tests. Mainly carried out improvements associated with the strengthening of the individual construction sites. Milyutichev flew one without a second pilot - a flight engineer PV Kormiltsev (and often without it). Now it seems like a surprising fact, but then, in terms of increased risk, it was considered normal. The factory program lasted until the end of 1954. Finally, the state commission demanded to make 10 flights lasting at least two hours. It was only after their execution state tests were continued. They contributed to the acceleration of GM Defense Minister Zhukov. Looking around in January 1955 a new aviation equipment at the airport Flight Test Institute, the famous marshal asked the Commander of the Air Force PF Zhigareva expedite the flow of arms to the latest heavy helicopter. In April of the same year, the Yak-24, state tests completed with positive assessment and was transferred to series production.

In 1955, a helicopter piloted by EF Milyutichevym, first shown at the air parade in Tushino. The following year, in the Aviation Day, flew four Yak-24, landed on the airfield Tushino troops with military equipment. Crew commander serial helicopters were Milyutichev, Research Institute of the Air Force pilots and Brovtsev SHishov pilot FRI Garnaev.

The Yak-24 helicopter dmonstrated reliability in long-distance flights on the route Moscow-Leningrad, binding EDO AY Yakovlev with his branch and serial factory. The first test flight took place on October 23, 1954 The crew of the second pilot to Milyutichevu invited Garnaeva and flight engineer flying AA Samsonov. Starting from the aerodrome curfew in Leningrad, headed for Moscow. On the route weather began to deteriorate, and the approach to Kalinin, the Yak-24 was in a storm with heavy rain and clouds to the ground. Dispatching service Kalinin airport banned the continuation of the flight and the crew landed.

The first non-stop flight (total of 4 hours 38 minutes) took place on May 30, 1955, when the Yak-24 was prepared in Moscow for the parade. The crew consisted of two people: Milyuticheva and mechanics Samsonov. Until 1959 Milyutichev already performed 12 such flights, of which four he flew only a mechanic. In other flight test pilots took serial A.Semenov plant part, N. Mokin, OA pilot FRI Syromyatnikov, were student (school test pilots) V.Gromov and Mechanics A. Samsonov, AN Bukin, V. Muzhchinkin. The flights were not easy for the pilot, which is almost five hours driving the aircraft intently, constantly working the handle and pedals. Only since 1957, when the Yak-24 entered service, were damping devices for the automatic flight stabilization in the control system, long flights are no longer tedious and even found some comfort.

Among the variations of the shape empennage change existed and option with the endplate. This option gave the worst results - breakdown already advancing at a speed of 120 km / h. The best - a combination of a stabilizer mounted at an angle of 10 in combination with a modified profile of the keel (asymmetrical, curved to the left side). Furthermore, of the wing area was increased. After experimenting with the tail, since there was a window in the State trials, it was modified intake system and cooling motors. Revised engine cylinder temperature is able to completely drive in the limits of tolerance.

Acting on the results of state tests of the Yak-24 helicopter, Air Force Commander Air Chief Marshal Zhigarev approved the helicopter on April 30, 1955. The military put a little list of the 274 Act of defects and shortcomings. The vast majority had already eliminated, there remained unresolved about two dozen. The main thing - it did not meet the requirements of the practical value of the ceiling. Among the unresolved deficiencies encountered some were very strange. Military wrote: "To provide for the possibility of modifications to the sea for use as an anti-base". Ehrlich wrote to Chief Designer: "Run impossible Navy did not issue demands." One hand does not know what he is doing right. Air Force ordered the naval version, and the fleet seemed to have no clue about it. All pilots pointed out the lack of stability (the helicopter was neutral for all three control channels), more or less stable could be considered only longitudinal channel in the air at high speed. It seems neutral stability considered a necessary evil.

February 14, 1955 adopted a decision according to which for the introduction into series production helicopter Yak-24 at the Leningrad plant # 272 created the Moscow branch of OKB-115. From October 1955 to March 1960 under the leadership of the branch team and with the active participation of the IA Ehrlich engaged in the improvement of the Yak-24 design, the development of modifications, expansion of applications, carrying out for this close relationship with the operating unit of the flight in Torzhok.

The serial prodcution helicopter Yak-24 again had problems with vibrations. Establishing the true cause of the vibrations resulted in a long search, and the main role belonged to B.Ya.Zherebtsovu. It turned out that the shaking occurred as a result of the interaction of elastic vertical bending of the fuselage and control system of the common oscillation step front and rear screws, connected by a rigid control wiring, hanging on rocking along the ceiling of the fuselage. Replacing the hard wiring with soft wiring finished the dangerous vibrations forever. The helicopter returned to the long blades, which significantly increased the capacity of the rotors.

The serial production Yak-24 was used in three versions: troop, transport and ambulance ["sanitary"]. The main characteristics of the helicopter were as follows: the nominal take-off weight - 14140 kg, empty weight - 10477 kg, speed - 175 km / h, the static ceiling - 2000 m, range - 395 km (range with additional 3rd tanks in the cargo exceeding 1000 km ). The fuselage of welded truss length of more than twenty meters in height and a width of 1.91 m placed triple crew cabin, two piston engine AL-82V nominal capacity of 1430 hp each with forced air cooling, transmission, control units and fuel-oil system. The helicopter had two 4-blade rotor 20 meters in diameter and 4-wheeled non-retractable landing gear in flight with a track width of 5 meters. At the rear of the cargo compartment, the length of which it is equal to 9.45 m, located fold loading bridge. As it made loading and unloading of goods and military equipment.

Modification of the Yak-24U was created as part of the airborne troops. The main requirement is to give the helicopter's ability to transport inside the fuselage whole range of military equipment Airborne, including self-propelled artillery units ASU-57, the payload mass is doubled - from 2 to 4 tons. On the external sling helicopter had to be capable of carrying trucks GAZ-51. At the same time resolved and clean air objectives for improving the stability and controllability; goal - to make a helicopter on a level comparable with the sport piloting the aircraft.

An interesting modification of the Yak-24 began in the embodiment pipelayer ("Nerpa" / "Seal" system). The backbone of the Soviet Army for decades remained the tank forces. A tank is known to be a voracious beast. The rapid advancement in great depth is impossible without a reliable supply of combat vehicles fuel. The most efficient method of supplying a fuel pipeline. Someone's bright head hit upon the next link in the logical chain: "The best means of pipe-laying is a helicopter." And from the helicopter was required in semi-automatic mode to dump pipe from a low altitude along the route of the future pipeline. "Seal" system intended for transporting and automatic layout of pipes along the route by helicopter field pipeline PMT-100. The pipe-laying device was installed on the serial helicopter Yak-24 head. # 03310. It included a set on the sides of the fuselage removable cartridge with a capacity of 44 tubes each. Tubes were placed in a cassette in two rows. Discharge of pipes was produced automatically turn to the right and left side.

Adopted in 1951, the decision to reduce the time and simplify the production of the welded truss fuselage by using a similar design to the Yak-14 landing gliders played a role in the fate of the Yak-24 helicopter. The use of welded construction prodiced a large vibration which proved undesirable. Therefore, all three projects under development provided for the monocoque fuselage structure. Tehse were the Yak-24R (scout), equipped with radar detection of submarines, surface ships and low-flying targets at a distance of 150-200 km with altitude up to 3000 meters; and Yak-24P with two turboprop designed by Ivchenko; and the helicopter-crane with a capacity of 40 tons with four gas turbine engines D-25B designed by PA Solovyov. Development work on the recast of the Yak-24 helicopter in the eight-passenger helicopter, special purpose Yak-24K ("comfortable" - komfortabelnyy) in late 1959 - early 1960 began be the staff of the Leningrad branch of OKB AS Yakovlev.

NS Khrushchev in the USA and in anticipation of the return visit of Dwight Eisenhower, September 18, 1959, IA Ehrlich was urgently summoned to Moscow. The CPSU Central Committee in the presence of the Deputy Minister of Aviation Industry SM. Leshchenko them with ML Mil charged as soon as possible to create a special-purpose passenger helicopter for a meeting of the American president. The situation was complicated by the fact that by this time the plant had changed the profile and all the work had to focus in only one former assembly shop.

Changing the design of the diagonal struts in the side panels of the fuselage farm allowed orfanizing eight huge square windows in the cabin the size of 900 x 900 mm and to dismantle engines without disassembling the interior. The second change was to the original design of entrance stairs (not the prototype, there is a door on the Yak-40 plane). Design and conversion of two serial helicopters with factory #2720803 and #2720804 happened simultaneously. It is difficult to believe that the first helicopter was converted and passed all the tests in just 40 days!

In the passenger compartment there were installed eight swivel chairs comfortable design with low back, soft and semi-soft seats wide leather armrests. Upholstery chairs was made of gray woolen fabric. Armchairs turned and could be locked in any intermediate position. Between the middle seats (front two series were against the motion) equipped with two tables and two wall vases. The front bulkhead clock and instrument panel were installed. four lighting the ceiling were provided, push-button alarm to call the steward and phone to communicate with the crew.

The rear lobby longitudinal wall was divided into two parts, one of which was a toilet provided hot and cold water. Another housed a snack bar with a set of necessary household items and wardrobe. Door-ladder was duralumin construction with ladder rungs, electromechanical controls and with folding handrails. Hoist entrance stairs consisted of the executive electric mechanism, two power rockers, spring cylinder, the rubber damper and rocker with limit switches. However, despite the impressive list of positive characteristics of the helicopter Yak-24K, the Mi-4 wong the competition.

The May 1960 events with the U-2 aircraft, which led to the deterioration of relations with the United States, apparently, affected the fate of the comfortable Yak-24K helicopter and career of his chief designer. The OKB AS Yakovlev built a 30-seat passenger helicopter Yak-24A, but this work was carried out without the participation of IA Ehrlich. Moving to work in 1960 as Deputy Chief Designer NI Kamov in the team Ukhtomsky Helicopter Plant, Igor engaged in coaxial helicopters and proved himself a great master in the testing and refinement of these machines.

From 1960 to the present day development of longitudinal helicopter in the Soviet Union stopped. The question arises - why? It is known that a longitudinal screw arrangement has several drawbacks, but at the same time a number of advantages over classic single-rotor circuit. The famous designer of aircraft and helicopters, compatriot II Sikorsky, was an opponent of the twin-screw longitudinal scheme, but its American competitor Piasecki did not bother with the inconveniences. His firm simultaneously with the Yak-24 was built in 1953 as a time machine to the longitudinal scheme. To this day, US helicopters fly longitudinal scheme CH-47 Chinook manufactured by Boing-Vertol.

The Air Force Museum in Monino remained the world's only exhibit of Moscow - the Yak-24 helicopter with a factory #27,203,310. Unfortunately, time was not kind, with rotted plywood replacing the fabric covering. Leningradsky North zavod, out of the gate of which in 1957 rolled out the helicopter, Director General GP Gardymov decided to help the management of the museum in the restoration of the helicopter.

Modification Yak-24
Diameter of the main rotor, m 2 x 20.2
Length m 21.34
Weight, kg null 10607
normal takeoff 14270
maximum take-off 16800
engine type 2 PD Shvetsov Ash-82B
power, kWt 2 x 1268
Maximum speed km / h 173
Cruising speed, km / h 150
Ferry range, km 1300
Practical range, km 650
Range with maximum load, km 255
Practical ceiling, m 5000
Static ceiling, m 2700
Crew 3
Payload: 30 soldiers or 18 stretchers or 4,000 kg of cargo

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Page last modified: 21-10-2016 18:40:25 ZULU