Myasishchev Molot - M-4 / Mya-4 - Design
The plane was created factory designation "product M" (theme - 25, in correspondence also met the designation "RRT" - high-speed long-range bomber). Time for the schematic design was released the minimum, which is not allowed to engage in long-term study of alternative arrangement, a problem to be solved is extremely complex. It should be recognized that when the first version of the machine was made a number of important steps, very bold and unconventional, without which this project would not have taken place.
After reviewing various options for the power plant, Myasischev concluded that the only acceptable are engines AM-03 design Mikulin thrust of 8700 kgf. They were large and heavy, with significant fuel consumption, however, they provided sufficient thrust to use only four motors and eliminated the transition to overly complex multi-engine layouts like the B-36 or B-52. But these engines and at first it seemed a little, so the aircraft began to design a starting rocket boosters and even a giant rail-ejection device, remaining unclaimed.
To achieve high flight performance, everything possible was done. In the final version of the layout, the engines were “hidden” in the root of the wing center section to reduce drag, and the latter were deployed several degrees outward to reduce the impact on the glider of hot jets flowing from their nozzles. Such an arrangement of engines was widely used not only by the British on the first heavy jet aircraft. A.N. Tupolev, creating the Tu-16. However, the difference between the Tupolev machine was the fastening of the turbojet engine not on the power ribs, but on the fuselage in the side recesses. This did not give the subsonic aircraft special speed advantages, but deprived the car of the possibility of replacing the AM-3 engines with more powerful and economical ones in the future. When creating the M-4 bomber, the designers apparently immediately understood these potential shortcomings and “hung” the turbojet engine on power ribs (later this came in handy on the 3M machine when they began to install VD-7 engines instead of AM-3). Each turbojet engine had its own air intake, which completely excluded their mutual influence. All free internal volumes of the wing with an extension of 8.65 occupied the fuel tanks. According to the design bureau, similar wing lengthening in combination with a flexible design ensured the optimal ratio of mass and aerodynamic quality of the airframe with the required margin of safety. For comparison, we note that for the Tu-95 bomber, a wing with an extension of 8.83 was chosen. Close to these values, the elongation of the overseas Boeing B-52 bomber of 8.44 was also chosen.
As for aerodynamics, the designers considered the most promising use of wing sweep 35 ¦. Magic figure "35", meets on most machines of that period, had a rather banal explanation - it has been bred in the process of working out a painstaking MiG-15 and Tu-16. To do this, had to spend a large amount of "trubochasov" during experiments in wind tunnels, which was very expensive. But calculations showed that the resistance of the wing is too large and does not allow to obtain a desired rate. Then Myasischev took quite a difficult decision: to increase the sweep, risking to lose during takeoff and landing qualities.
To reduce the structural weight was considered the preferred propulsion engines on the wing, removed from the fuselage so that the weight of acting against the lift, "unloaded" wing, which can make it easier. But then the nacelle would increase drag, and increased surface area bathed by the increase in resistance caused friction. Given this, the new plane engines entered into thick "roots" of the wing, and they almost do not protrude beyond the bypass. Moreover, the jet streams for accelerated flow behind the wing near the fuselage fairings and played the role of improving the flow around the aircraft in this difficult place.
The swept wing has bad stalling characteristics. This problem can be combated by various methods, including the aerodynamic setting ridges using different profiles on the wing. Wing aircraft, "M", in addition to these solutions, received significant geometric twist. The end zone had a much smaller angle setting than the root, and when entering the high angles of attack continued to "carry" when the root already started breakdown. As a result, the plane had to move to a smaller angle, as well as not to lose controllability on a roll, as ailerons continued to operate normally.
In the mid-1940s. in the U.S. for the first time in world practice on a heavy aircraft B-47 has been used safely deformable wing design. It has become much easier, while maintaining strength. The successful experience of application and received at the intercontinental B-52. From foreign aviation magazines it was known, and despite sharp criticism from some prominent experts and TsAGI VIAM Myasischev went down the same path. Calculations showed that in-flight wing tips will fluctuate with amplitude up to 2 m, and later, on the static tests, rejected them from neutral as much as 5 m!
The design of the aircraft for the first time on a heavy bomber was used a number of new materials, and above all, high-strength aluminum alloys B-65 and B-95. They are at the same relative weight that D16T, had high strength but greater rigidity and consequently poorer fatigue characteristics. For a typical flight lasting 15 hours aircraft could save more than 2500 cycles of loading ("Mach" wing). On some aircraft, created with the use of these alloys, the fatigue failure of nodes caused serious accident, Myasishcheva managed to make a machine with sufficient resources, which was subsequently confirmed by practice.
Observing strict economy of weight, the designers did not stint on the powerful weapons. Nomenclature offensive, except nuclear weapons, included conventional bombs caliber from 500 to 9000 kg, sea mines, torpedoes and guided bombs ASD-2000F. The maximum bomb load was 24 tonnes, which is 2 times higher than the possibility of Tu-95. Defensive armament consisted of three two-barrel gun remotely controlled installations had spherical shelling, while at the Tu-95 was a dead zone at the bottom of the front hemisphere. It should be noted that the Americans equipped with B-52 generally one feed machineguns, because believed that the probability of a successful attack speed bomber in the forward hemisphere is close to zero.
Calculated at speeds, the load controls already exceeded physical capabilities. In those days there was no consensus on the methods for solving this problem. Tupolev saw a way to improve the traditional mechanical control system by reducing the frictional resistance and optimize kinematic parameters. The result is a relatively easy, simple, cheap and reliable system that has been applied on the Tu-16. Know a maximum speed, and hence the load on the control surfaces were less than that of a jet bomber Myasishcheva for which should create a system of another type.
In Germany during World War II management system was developed, which included motors, which have applied for German specialists built aircraft in the USSR "150". Myasischev carefully studied it, but found it too difficult, not reliable enough and hard in the final design. Had to make a choice in favor of the hydraulic booster. When using it, the pilot control spool booster rods through the lungs, and the load on the steering wheel and pedals simulated spring mechanisms.
For bomber "M" were provided ejection seats of all crew members. While designing such access was assigned to the aircraft developer has created his chair and DB-23. All crew members ejected downwards.
During the creation of the aircraft were built full-size models of the front and aft cabin, bomber as a whole, as well as many stands, including hydraulics and chassis, power plant control system. For practicing the most difficult decisions used flying laboratory, which was converted into three Tu-4: Tu-4SHR - test chassis, Tu-4DR - test engine AM-03, Tu-4UR - for control systems and ejection seats. Testing of the power plant units, as well as pieces of armor, including bombing radar and optical sights, navigation and communications, conducted several research aircraft in specialized organizations. TsAGI strength tests were separate panels and units of the plane, as well as statekzemplyara machine (factory - 4100002).