An extraordinary event in the world of domestic helicopter construction took place on July 3, 1952, when the crew commander Sergey Brovtsev made a long flight on the Yak-24 for the first time. On that day, domestic specialists celebrated an undoubted success. After all, the "24th" became the first twin-screw helicopter of the longitudinal scheme in our country. Moreover, in terms of engine power and payload, it surpassed all Soviet and foreign machines at that time.
It may seem strange that the Yakovlev Design Bureau, which was considered a recognized leader in the creation of light—engine aircraft, which developed front-line fighters with liquid-cooled engines throughout the war, suddenly took up a new topic - helicopter construction. But, firstly, Alexander Yakovlev's team still had some experience in creating helicopters. Secondly, the desire of the country's leadership to attract fresh people to the work in the hope of seeing non-trivial solutions that would make it possible to achieve a rapid breakthrough in this area was guessed.
Alexander Yakovlev
From the book "The Purpose of Life"
On the way to the "24th"
Since the end of 1943, engineer Leonid Wildgrube, transferred to the Yakovlev Design Bureau, worked on the issues of aerodynamics and design of rotor blades, working together with the Central Aerohydrodynamic Institute (TsAGI). A small group of semi-artistically developed a coaxial helicopter with M-11 light engines, which received the designation EG (experimental helicopter), and the index Sh. Unofficially, the product received the code "Joke".
On the instructions of Alexander Yakovlev, a group was created, which included Nikolai Skrzhinsky, who was engaged in gyroplanes (rotary-wing aircraft) in the 1930s, an experienced engineer Leon Shechter and several designers who took part in the construction of Soviet experimental helicopters.The project, originally named Yak-22, was headed by a veteran of the Russian helicopter industry, Pyotr Samsonov. Soon the experimental machine was renamed the Yak-100 — a single-rotor transport helicopter with a tail rotor was built by 1948. Nevertheless, it was not built serially, since the Mi-1 helicopter of the Mil Design Bureau, which was being tested at the same time, showed higher characteristics.
To work on the Yak-100 project, Samsonov attracted the future leading designer, and then a young engineer Igor Erlich, who since 1947, after graduating with honors from the Moscow Aviation Institute, began working in the design bureau of the chief (later general) designer Alexander Yakovlev as a calculating engineer and was engaged in ensuring the dynamic strength of aircraft. It was during those years that a promising specialist gained experience in design, testing and finishing work.
Thus, the development of a unique at that time 24-seat helicopter of the longitudinal scheme began on September 24, 1951 and was led by an already established group of specialists, and the design was carried out on the basis of broad cooperation with the involvement of the country's leading research institutes of the relevant profile: TsAGI, CIAM, VIAM, NIAT, LII, etc. Excellent coordination of activities made it possible to complete the design work in an exceptionally short time — already on December 10, 1951, a mock-up commission chaired by Air Marshal Nikolai Skripko reviewed and approved all the submitted materials of the future helicopter.
The military had no doubt: the army needed such a car. From the beginning of the following year, the center of gravity of the work on the production of experimental helicopters moved to Leningrad, where Yakovlev organized a branch of his design bureau and where he sent Ehrlich and a number of other employees. The upcoming construction of prototypes in Leningrad required the release of a large number of drawings, which could only be done with the direct manufacture of the machine, as they say, "locally".
Design features
In accordance with the preliminary design, the helicopter was made according to a twin-screw longitudinal scheme with two piston engines and a four-support non-retractable landing gear. The rectangular-section fuselage had a truss structure made of steel pipes covered with a canvas skin, and consisted of three parts: the nose with a crew cabin and a radio equipment compartment, the central one with a cargo cabin and the tail one with a large rear rotor pylon. There were two pilots and a radio operator in the three-seat cockpit. There was also a mobile rifle installation with a machine gun.
The cargo cabin, measuring 10 x 2 x 2 m, had a hatch designed both for transporting goods on an external suspension and for loading people and equipment in the hovering mode. The Yak-24, created primarily for military purposes, allowed transporting 20 paratroopers in full gear or up to 12 wounded accompanied by a medical worker. Guns, mortars or vehicles of the GAZ-67B or GAZ-69 type were transported in various combinations. The power plant consisted of two ASH-82V piston engines mounted under the main screws with gearboxes and synchronizing shafts. The propeller control system is a booster with power steering, with the inclusion of an autopilot in it.
Debugging takes longer to create
If they created the Yak-24 quickly compared to other devices, then they brought it to mind for a long time. 142 flights were performed during factory tests alone. OKB veterans believe that the appointment of two pilots: the experienced Sergey Brovtsev, soon awarded the title of Hero of the Soviet Union, who gave a ticket to the Yak-100 sky, and the novice tester Egor Milyutichev — was an exceptionally successful decision that favorably influenced the refinement of the machine, since these people complemented each other in character and work.
Two experienced helicopters were tested in a variety of modes, including its ability to hover in the air motionless at zero speed, while lifting a large load vertically from its place. A significant problem that was revealed during the tests was a significant vibration of the structure.
There was an assumption that the source of strong shaking are the blades — with their rapid rotation, complex mechanical and aerodynamic phenomena arose. In order to determine exactly whether this is the reason, the head of the research department of the OKB A.S. Yakovlev, Claudia Kildisheva, suggested cutting off half a meter from each blade and seeing how this would affect the shaking of the entire structure. The flights performed by Brovtsev and Milyutichev showed that such a strong vibration stopped in all modes.
But, having defeated one serious "disease", the developers faced another — related to the insufficient lateral controllability of the helicopter. So, in 1955-1956, two Yak-24 crashes occurred in a deep roll with sliding. Nevertheless, we coped with this problem.
These helicopters did not have to fight. Although flight accidents did happen (for example, cars fell from a low altitude three times), however, during the entire operation of the Yak-24, which were often called "flying cars", we can say that they were lucky with them: no one died during the tests or later (which is rare in the international history of aviation technology).
Flights on the Moscow — Leningrad route connecting the Yakovlev Design Bureau with its branch and serial plant were supposed to demonstrate the reliability of the machine. The first test flight in October 1954 did not become non—stop - due to a sharp deterioration in the weather, the crew had to land in Kalinin and wait out a storm with a downpour. On May 30, 1955, the Yak-24 was nevertheless driven to the capital without intermediate landings — the total duration was 4 hours 38 minutes. Milyutichev piloted the car, as in many other cases, and Arkady Samsonov, a permanent flight mechanic, was next to him. Yuri Garnaev also flew a lot by car.
In 1955, a helicopter operated by Egor Milyutichev was first shown to the general public at an air parade. Alexander Yakovlev felt that it was time to demonstrate the true capabilities of his rotorcraft. At the airfield in Tushin on December 17, a Yak-24 under the control of the same Milyutichev lifted a cargo weighing 4 thousand kg to a height of 2,902 m. Then an experienced tester (mastered about 100 aircraft) Georgy Tinyakov with a cargo of 2 thousand kg reached 5,082 m on the "24th". The flight results turned out to be record—breaking for cars of this class - the International Aviation Federation (FAI) approved them.
Difference of schemes
In the Yak-24, two engines (located in the bow and stern) united by a common transmission, which rotated two bearing rotors in opposite directions, each with a diameter of 20 m. Thanks to such an original transmission design, both rotors could work even in the event of a failure of one of the engines (reliable piston engines and ASH-82 aircraft engines developed during the war with a capacity of about 1,650 hp each).
The longitudinal arrangement of the screws, although it has a number of disadvantages, but at the same time it has a number of advantages over the classic single-screw scheme today. The famous designer of airplanes and helicopters Igor Sikorsky, who is rightly considered the founder of helicopter construction, was an opponent of the twin-screw longitudinal scheme, but his competitor, the American Pole Frank Piasetsky, was not at all embarrassed by some inconveniences. His company Piasecki Helicopter Corporation almost simultaneously (in 1953) with the Yak-24 built a machine of just the longitudinal scheme, which was waiting for a long life — to this day helicopters of this scheme CH-47 Chinook fly.
In Leningrad, a series of 40 Yak-24s was laid at plant No. 272, and 35 units were built and handed over to the customer (excluding experienced ones). No more helicopters of this type have been designed or built in our country. The creation of the Mi-6 heavy helicopter by Mikhail Mil's team, which became exceptionally successful and launched into mass construction, removed many questions: equipped with two turboshaft engines with a free turbine, it was the most lifting helicopter of its time, the layout scheme of the Mi-6 was recognized as a classic.
Igor Erlich remained a supporter of the construction of helicopters of the longitudinal scheme in the USSR, repeatedly trying to prove the advantages of those solutions that were incorporated in the Yak-24 (even though he had worked at the Ukhtomsky Helicopter Plant since 1960 as deputy chief designer Nikolai Kamov, and the local leadership held different views). After the accident at the Chernobyl nuclear power plant, Ehrlich, along with other helicopter pilots, took part in monitoring the air situation over the destroyed reactor, which negatively affected his health - the talented designer, winner of the Lenin and State Prizes of the USSR died in June 1988 at the age of 66.
Civil application
I think it would not be a mistake to say that the Yak-24, created primarily for the army, paved the way for the widespread use of helicopters in the national economy. These machines had a chance to work as a pipelayer, significantly speeding up construction processes in the Leningrad region, and then during the laying of a section of the gas pipeline through the Novgorod marshes. The Yak-24 delivered large gasoline tanks over considerable distances to hard-to-reach areas, served as cranes, and practiced the use of helicopters in mountainous terrain.
When the restoration of the Catherine Palace, destroyed by the Nazis during the retreat, began in Pushkin near Leningrad in 1959, it was necessary, among other things, to replace 30 wooden trusses-rafters with new metal ones. The Yak-24 crew required filigree precision, the helicopter itself also demonstrated its best qualities, hovering over the building without swaying. It could take months to solve this difficult task, and with the help of the Yak-24, builders and restorers coped in two windless nights without damaging the century-old trees and the buildings surrounding the palace.
Unfortunately, special civilian variants, such as the "flying crane" with an increased payload capacity of up to 5 thousand kg Yak-24A, with a shortened fuselage and a VIP cabin Yak-24K or with new gas turbine engines Yak-24R, could not be launched in series.
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