Myasishchev Molot - Bicycle Landing Gear
The bicycle chassis, so strongly proposed by Myasischev and used on an airplane, is worthy of detailed consideration. This type of take-off and landing gear in aviation has been known since 1910. One of the pioneers of aircraft construction R. Esno-Peltri equipped it with its airplanes. In different years, such a chassis met occasionally. In the USSR, except for the fighters R. L. Bartini “EI” and I-240 (their chassis was unicycle), it was first designed in 1941 by I.V. Chetverikov for the I-1AM-37 fighter and was developed in 1949 for the flying laboratory, which they wanted to do on the basis of the UTB-2 training bomber (a lightweight version of the front-line Tu-2). This flying bicycle stand at TsAGI was started by I.P. Tolstykh, a well-known designer of gliders and light-engine aircraft of the IT brand in the 1930s.
For the installation of new racks by the UTB-2 case, it was planned to design a special multi-tube truss trimmed at the bottom by bolt mount assemblies. It would allow changing the position of the struts of the investigated chassis relative to the center of mass of the laboratory airplane to find the optimal position and tilt of the wheel bearings relative to the main units of future aircraft with a bicycle chassis. Scientists of TsAGI commissioned work on the creation of this apparatus in connection with the creation of an average 150 bomber at OKB-1 of plant No. 256, where German aircraft designers were brought back to in early 1947. The general management of the “imported” (more precisely, prisoners of war or even contribution) specialists was carried out by the aircraft designer S. M. Alekseev, who in 1948 was appointed head of the German OKB, and in 1949 the chief designer of OKB-1 for jet bombers.
The creation of landing gear for the "M" was a very difficult problem. After working several options the choice was made in favor of the little-known at the time the bicycle scheme with two main pillars equipped with four-wheel bogies. To ensure stability when driving on the airfield used small supporting pillars on the wingtips. The main reason for this decision became layout considerations, as well as a significant gain in weight compared with traditional terhopornym chassis. Earlier in the USSR, such a scheme was used on an experimental fighter Alekseyev I-211, which flew successfully, but tests have shown that it is difficult to raise the plane's nose during takeoff. You can immediately ask takeoff angle, using racks of different heights, but the increased length of the runway due to the increase of resistance. The solution was found in the original decision. The plane began the run with a lay angle, speed increases the lift of the wing gradually compensated weight, pressure in a special ram bow supports squeezes rod which turned the truck so that the land concerned only the rear pair of wheels (so-called mechanism "vzdyblivaniya"). Aircraft's nose lifted created takeoff angle, and the machine was coming off from the strip with almost no intervention by the pilot.
Bike chassis so strongly suggested Myasishchev and use on aircraft, adequately detailed consideration. This type of runway devices known in the aviation industry since 1910 They equip their airplanes one of the pioneers of aircraft R. Esnault-Pelterie. Throughout the years, the chassis is encountered sporadically. In the USSR, except fighters R. Bartini "EI" and I-240 (their chassis was Unicycle), it was first designed in 1941 for IV Chetverikov fighter I-1AM-37 and developed in 1949 . for flying laboratory, which wanted to make on the basis of the training bomber UTB-2 (a lightweight version of the front of TU-2). This flying bicycle stand at TsAGI started IP Tolstoy, known in the 30s Designer gliders and light motor aircraft grade "IT".
To install new racks UTB-2 was scheduled special design multi-tubular trusses, edged along the ground nodes bolting. It would allow to change the position of the test rack chassis with respect to the center of gravity research aircraft to search for the optimal position and tilt wheel supports on major units of future aircraft with a bike rack. Work to create this device TsAGI scientists booked in connection with the creation of medium bomber "150" in the OKB-1 plant number 256, where in the beginning of 1947 were brought by German aircraft designers. General guidance on the "import" (or rather, war or even contributory) specialists carried aircraft SM Alekseev, who in 1948 was appointed chief of the German bureau, and in 1949 the chief designer of OKB-1 jet bombers.
Prior to the construction and experiments on the LL-UTB-2 is not reached, although this order TsAGI hooked and Myasishchev with GN Nazarov, who worked at that time in the MAI. To accelerate research on new gear is not "lab" exhibit, and on a real combat aircraft, S. Alekseev proposed to convert for "bicycle" your multipurpose jet fighter-215, which was close to the mass of UTB-2. Thus eliminating the industry from design and manufacturing of a special apparatus. It ready and is in flying condition-215 had only to equip the second leg with a new fuselage (larger diameter) and a pair of wheels to replace the wing (former chief) stands with pneumatics, Zadran their niche on the light side supports with suspension under their gondolas THD.
After closing the OKB-21, S.Alekseev 1948-215 remained at the plant number 21. In mid 1949 by a group of repairmen arrival with drawings and pneumatic rear chassis legs plane was altered to support cycling and after fly-by place under its own power (pilot IE Fedorov) forwarded to the factory number 256. finalized and-215D with the new chassis at takeoff and landing behaved in such a manner as though he had "born" with it. Tests were carried out so successfully that allowed us to develop and test, and then reproduce the bike chassis other firms: OKB-115 Yakovlev OKB-240 Ilyushin OKB-155 Mikoyan and certainly well, we are interested in DB-23 Myasishchev. As for the main customer on the I-215D - OKB-1 plant number 256, the bike rack in an enlarged form was created for the aircraft and "150" on the order of the heavier.
Together with the use of the chassis of this type on a large aircraft were well worked out and the idea of a simplified system design and short take-off compared with the start of a traditional tricycle landing gear. Was introduced and used so-called "squat" aircraft on the back foot, whereby the machine at the rate of separation (ie, equality between lift and takeoff weight) she lifted the nose and an increase of 3 ° angle of attack of the wing detached from the strip without taking the helm of the pilot control over. Take-off process was not only safer, but almost automatic when the pilot needed only to hold the car on the side of the stall and tracking engines at takeoff.
VM Myasischev and GN Nazarov obtaining authorization MAP thoroughly acquainted with the works of OKB-1 (for a couple of months Nazarov was sent to the plant number 256 and participated in the flight tests as the understudy lead engineer object "150"), which to a large extent been voted helpful topics "RRT". After careful consideration of this experience and attempt to try it on to their offspring revealed that for strategic bomber (at least three times heavier than an airplane "150") system "squats" back support in its pure form is not acceptable under the terms of operating loads based airfield. Designers managed to rethink the experience of others and to identify the implementation of simplified takeoff due to hydraulic front carriage chassis. Thus, in relation to a massive "bicycle" eight-chassis "RRT" managed to achieve the same effect at the start, and that for a single fighter I-215D and, of course, easier than "RRT" bomber "150".
Great importance was attached to the choice of the scheme and the main parameters of cycling gear and had a "home" developments. Even at the stage of preliminary design Myasischev recommended for bicycle bomber chassis as the most profitable in the mass ratio. Mass bicycle chassis is 3 - 3.5% by weight of the aircraft, while the same characteristic as a three-point circuit is in the range of 4 to 6.5%. Released from a squat fuselage (rather than high-wing, preferred for any bomber), is the chassis was the easiest because of the relatively short racks. Moreover, it relieved from all sorts of wing otbekatsley and superstructure embedded in terms of aerodynamics, and most importantly, from shock loads when taxiing, takeoff and especially landing. Compared with other schemes bike chassis is the most preferred for aircraft operation on unpaved airfields.
For these good reasons at the factory number 23 designers focused projects department (chief Selyakov LL) and Chassis Division (Head GI Archangel) was paid to the definition of the main parameters of the chassis racks. This allowed placing the main "flavor" of the aircraft - the bomb bay in the zone center of mass - and distribute fuel, equipment and other stuffing fuselage, as well as the very structure of the aircraft as almost equally between the wheel supports, and outside compartments chassis. For heavy aircraft this circumstance is perhaps the most important in terms of airfield operation. With such an important task designers coped very successfully: basing bomber was provided at existing aerodromes standard thickness of concrete covers. Control of the aircraft on the runway during the motion was dostipguto turning bow pair of wheels of the front carriage. At the preliminary design stage "RRT" basic questions of principle, of course, thought through, but by the time the government decree on the restoration of OKB became clear that the case is just beginning and have a lot to re-interpret and truly.
So, to practice cycling chassis closest to the actual weight of the M-4 long before the flight tests, a flying laboratory was created, but on the basis of the strategic bomber Tu-4. Following the example of earlier work on the LL-TSA-2 for a large plane was built powerful farm, welded steel tubing. Its design allows you to vary the position of the C-pillar to the center of mass of the Tu-4-LL. A series of test flights fully confirmed the calculations and predictions of scientists and engineers. She let good work piloting technique M-4 before his first departure. Test pilots from LII MAP began studying the peculiarities of the new chassis, highly appreciated the role of a flying laboratory. Also, there was a special modeling stand simulator, where pilots practiced skills automatic takeoff in relation to M-4. He has helped many pilots overcome the psychological barrier - to abandon the usual desire to help the aircraft fly over the helm of the movement.
In 1953, it was decided that in order to meet customer requirements, the aircraft needed to be further developed. On the second DM pilot flight vehicle No. 0003 (glider No. 0002 was intended for static tests), built in December 1953, a new landing gear was installed with a rising trolley, which increased the take-off angle of attack from 7.5 to 10.5 degrees (on production vehicles set 9.5 degrees). This technical solution was proposed then by a young specialist V.K. Carrasc Subsequently, such a nasal cart was placed on the M experimental machine, and on a serial one, No. 0508, a slow-lift cart was tested. Tested in 18 flights, the advanced trolley was recommended for installation on production aircraft.
the M-4 bomber was considered strict in piloting an airplane, especially at the time of take-off and landing. Pilots for a very long time could not get used to the fact that the jet bomber detaches from the runway “automatically”, only due to the operation of the “uplift” mechanism of the machine, and at the time of take-off it was only necessary to keep the aircraft in a straight line with the pedals and, if necessary, fend off the roll. Many pilots, guided by their subjective sensations, tried to “help” the bomber take off and took the helm on themselves, which could lead to very sad consequences.