Kraków 2016-03-24
Subjective article.
Tupolew Tu-144.
This article is not intended to compare the Soviet Tupolev Tu-144 postal airliner with the Anglo-French Concorde commercial plane, because these planes cannot be compared. Concorde was designed to carry 100 passengers at a speed of 2 Ma across the Atlantic Ocean. This plane still arouses admiration and respect today. The Tu-144 aircraft, on the other hand, was created from the rulers' complexes in the Kremlin and was based on industrial espionage, with the official position that it is the CCCP's own design thought. There it was said, "You know, you understand, we also have to have something like that." Someone may notice that the West was also spying, and it will be right. However, it was military espionage (defensive, defensive); to what extent the "doves of peace" released from Tu-95 bombers are a threat to them.
Labeling the Concord aircraft is flattery for the Tu-144, but an insult to Concord and appeared only in the 90s of the twentieth century. But the Tu-144 was really proud of the CCCP and the pride of AEROFŁOT, which was a carrier with the rank of ministry. Undoubtedly, there were many talented designers in the Moscow State. The problem, however, was that the technical education of those who turned this plane into reality was poor. As a result, after the break-up of the CCCP, most of the talented designers emigrated and found employment in the free world.
The Tu-144 is a really nice plane, actually two planes, two different models, which the authors who write about it do not notice. And we want to raise this matter. Another issue is the powertrain, about which the authors only give the facts, without much thought. And we will also deal with this matter.
Several supersonic commercial aircraft programs have been under development in the US and Western Europe since the early 1960s. This was known in the Kremlin. Khrushchev called another conference and, as usual, ordered the development of a similar structure by party orders. In all likelihood, CCCP intelligence captured the Concorde aircraft in France around 1964. The Kremlin decided to copy this construction. The program received the designation Tu-144, which was to suggest the continuation of the Tu-104 passenger aircraft development line. In order to be credible, in 1965, at the Paris Air Show, they showed a model of the future supersonic aircraft. Time was pressing, so the designers took shortcuts. For example, the complicated geometry of the Concorde airfoil is not adopted, limiting itself only to adopting a leading edge in arcs. In order to check this solution, such an airfoil was installed on the MiG-21 aircraft. The plane was called Analog 144. The machine was first flown in 1967.
Industrial espionage is questioned by many journalists. They indicate that airplanes differ significantly from each other. And if anything, they were just general plans. Not. The plans were accurate. Only the Soviet technique was not able to make an exact copy. They did not have the appropriate material and construction technology. Let us recall with what difficulty the Muscovites copied the B-29 bombers. As far as the airframe was relative, the replication of the engines failed and the Tu-4 bombers did not make a career. It was similar with all the plans that General Marian Zacharski obtained in the USA and which were transferred to the East. In the Kremlin, the feasibility of the solutions and technologies developed in the USA were doubted.
Problems encountered by the designers at CCCP.
The construction of the bombers at the CCCP was of a high standard. Large funds were allocated for this purpose, because bombers were the main force of the nuclear triad: bombers, submarines and ballistic missiles. However, the bomber is not a commercial aircraft. The crew fly frequently using oxygen masks. He has emergency systems at his disposal. In flight, a bomber often changes its altitude and course. To ensure maximum range and flight time, most of the route is at subsonic speed. Besides, there is a lot of noise in the bombers. The structure is not soundproofed because it increases the mass. Air conditioning is limited to the crew compartment (cockpit) only.
On a commercial plane, passengers will not wear oxygen masks. We will not train them in the use of ejection seats and the use of parachutes. The noise in the passenger compartment could not be greater than in the previous generation of airplanes. Air conditioning had to be much more efficient due to thermal heating of the structure. The passenger on board was to have comfort no lower than in classic airplanes. It was necessary to convince the passenger that his stay on board was completely safe and that he was participating in something unusual; for example, it can see the curvature of the Earth from an altitude of 18,000 meters, and the sky is deep blue.
One of the main problems was keeping the Ma 2-3 speed constant. Here we mention that Ma 1-1.5 speed is the least favorable in all respects. Mainly because of the wave resistance.
In order to understand all this, we will present how the flight of the Concorde plane looked like: Start with the use of afterburners, so that a DS / RWY would be enough. After that, afterburners turn off, because they use fuel the most. The plane is gaining altitude. At an altitude of 10 560 m, the typical ceiling of subsonic airplanes, the Concorde exceeds the speed of Ma 1. At the appropriate altitude, the afterburners are turned on again to accelerate the plane to cruising speed Ma 2. Just before the cruising speed, the afterburners are turned off. When the plane reaches Ma 2, it is already 1,000 km away from the take-off point. During the flight, despite turning off the afterburners, the plane accelerates even more, because the weight of the plane decreases due to fuel consumption. The speed can reach Ma 2.2. The plane flies like this because its engines have the ability to maintain supersonic speed without the use of afterburners, like the latest combat aircraft today. The descent for landing begins many kilometers before the destination airport. The plane lowers the altitude while slowing down. The airframe does not have airbrakes, as is the case with military planes. In order to shorten the coastdown, thrust reversers installed in the engines are used.
Tupolev Tu-144 power unit.
All this was known in the Moscow state. And it was known that their main problem was the lack of proper engines. While small and medium-power turbojet engines were reasonably good (although fuel-consuming), high-power engines were and are not available in Moscow. Any attempt to copy or buy such engines in the West has failed. The most serious attempt was the purchase of engines in the USA for Ił-86 passenger aircraft. Muscovites have almost reached an agreement with General Electric on the purchase of 12 General Electric CF6-50 engines. The CF6 engine is basically a large family of engines used to power wide-body aircraft. The first engine start took place in 1971. The engine at the beginning of the 70's was very modern and proved to be a successful design. But in 1978, the US Department of Commerce vetoed the export of 12 General Electric CF6-50 engines, ordered by CCCP, to the planned long-range Il-86 (Il-86 D). The Department of Commerce's reasoning was logical. If the Soviets want to build more than 100 Il-86 machines, they should order a minimum of 400 engines, not 12. Consequently, there is a reasonable suspicion that they want to copy the engines. The Soviets were also looking for their luck in the UK, trying in 1976 to buy a few Rolls-Royce RB.211-22 engines. This engine was launched for the first time in 1972. The British, however, did not sell these engines. After a few years, Deputy Minister Dondukov, Deputy Minister Alexander Gromyka, admitted that they intended to copy the engine and start its production.
In order to understand the problems of Moscow designers, it is necessary to look at how the Concorde aircraft engine was built. The leading force was the British company Bristol, which was more successful than the French Snecma. The solution was the Olimpus 22-R engine used to propel the TSR.2 aircraft, with a thrust of 2 x 146.80 kN (2 x 14 970 kG). The engine was single-flow with an afterburner. It was necessary to increase the engine thrust without afterburning with the same or lower fuel consumption. One of the ways was to develop an innovative electronic engine control system. The first such system in civilian engines. The computer program was to monitor its work without the participation of the pilot, regulate the air intake, air vents from the inlet channel and regulate the outlet nozzles and thrust reversers. Such a system could completely eliminate the third crew member. However, at that time, the regulations did not allow two-man crews on Atlantic flights. A joint effort of both companies (Bristol and Snecma), the Olimpus 593-1 engine with a thrust of 128.70 kN (13,080 kG) was created. Then there was the Olympus 593-2B engine with a thrust of 146.41 kN (14,930 kG). Then: Olympus 593-3B with 154.65 kN (15,770 kG) thrust, Olympus 593-Mk.602 with 169.26 kN (17 260 kG) thrust, Olympus 593-Mk.621 with 177.50 kN (18 100 kg). Maximum thrust is not that important. Maximum thrust without afterburning is important, with the lowest fuel consumption at the same time, because it affects the range. Afterburning in this engine is only 17-20% of the total thrust. In military aircraft engines, afterburning increases thrust by 50-100%.
We will also note that this is a single-flow engine, not a two-flow or even fan engine, so it consumes more fuel by nature. However, its advantage is a small frontal area, which results in a more streamlined shape of the entire plane and lower aerodynamic drag. If you were to build a Concorde plane with two Olimpus 593 engines, it would take 30 passengers on board. And if it had six such engines, it would take 200-220 passengers on board.
What did the Moscow state have in the mid-60s? It is officially reported that the first Tu-144 planes were powered by Kuznetsov NK-144 engines. They developed a thrust of 4 x 127.48 kN (4 x 13,000 kG) without afterburning and 4 x 174.55 kN (4 x 17,500 kG) with afterburning. From the dry data, it looks pretty good. So what was the problem of the Moscow designers? In 60 years, the mosquitoes had good WD-7 engines with a thrust of 127.50 kN. These were single-flow engines, without afterburning, mounted on the Myasiszczew M-4 bombers and their derivatives, as well as Tu-22 bombers. The engine was developed by the team of Vladimir Dobrynin around 1955. It was then the most powerful turbine in the world. These bombers, however, were quickly decommissioned in favor of the turboprop Tu-95 / Tu-20. The WD-7 engines were equipped with afterburners, which allowed for a thrust of 176.52 kN (18,000 kG). This engine weighs over 3,000 kg.
We will cite one more fact. The task faced by OKB Myasishchev on 07/19/1955 was to build an intercontinental bomber capable of taking a thermonuclear bomb weighing about 5,000 kg, transporting it to a distance of 6,000 km, dropping it in the area of the target and returning to its own airport another 6,000 km. This range was to be achieved without refueling. The plane was to fly over enemy territory at a cruising speed of 1,700 - 1,800 km / h. Someone will say that these conditions were impossible to meet. Unfortunately a bug. They were to be met. Few people remember that at that time work was carried out on nuclear-powered turbojet engines. This is a topic for a separate article at all. The M-50 bomber was developed for these conditions. As the "nuclear engine" program turned out to be very dangerous, the concept of conventional propulsion was reverted to.
The above-mentioned engines, referred to as WD-7D, were used to power the Myasiszczew M-50 bomber. We'll stop by this plane for a while. The bomber received four such engines in individual nacelles. The hull was long, spindly. Bicycle type chassis. Delta wings, with an area of only 250 m2. Classic tail. The plane was flown on September 15, 1959, or October 27, 1959. It was shown to the public in flight in Tuszyn in 1961 and 1967. The bomber was supposed to reach Ma 3 speed. In fact, it flew at a maximum speed of 2,200 km / h, and the cruising speed was only 1,500 km / h. The plane made about 25 test flights. It required long DS / RWYs to take off and could not be used from all airports. Therefore, the next version was to have extreme downward-tilting engines. However, the biggest problem was the range, only 3 200 km. As we can see, the M-50 plane could not be used as a base for a passenger plane. Although there were such fittings. On the other hand, the experience gathered was extremely valuable.
We can equate the WD-7D engine and the Kuznetsov NK-144 engine and say that it was the same design. However, it must definitely mean that the gondolas of the M-50 were very simple. The air intake ducts were not developed in them so that the air before entering the engine had the appropriate parameters, i.e. it fell into the engine at a subsonic speed. In this, the designers saw a failure, and after getting information about how the problems were approached in the West, it was decided to change it. Theoretical and laboratory tests showed that the engines could be assembled into one package. Among the benefits, attention was drawn to a smaller outer total area of the airframe, and thus lower frictional resistance. In turn, placing the engines at the rear of the fuselage reduced the heating of the airframe caused by working engines. The air grips for the engines themselves were equipped with a system of movable flaps, generating specific oblique shock waves, which slowed down the air, and already had a subsonic speed in front of the engine. There was not much time, so the air intake ducts were designed disproportionately long, which contributed to the poor operation of the power unit in the future. The use of the package turned out to be a failure in the case of the Tu-144, because the WD-7D engine had a very narrow range of stable operation. (No controllable vanes in the first stages of the compressor.). In the event of one of the engines stalling, disturbances in the air before the air intake caused the engines to fall out of motion. Dangerous situations arose then.
The engines were equipped with thrust reversers. However, they were ineffective and had a lot of weight. Therefore, he resigned from them. Three or four parachutes were used to shorten the run-up. It is hard to imagine that a plane would land with parachutes at a normal airport. Who would then collect them from the taxiway? Who would put them together and reinstall them in the tail of the plane? Let us remind you that when the Tu-104 visited Warsaw at the Bemowo Airport, he also had to use braking parachutes. Varsovians were then explained that DS / RWY in Bemowo was short. It was a strange translation, because the Bemowo Airport, at the beginning of the 1950s, was built by the Soviets in Warsaw for their own needs, according to their plans. (The airport was built by Polish companies). Why did the Soviet airport not fit the Soviet plane? This was the main reason why LOT Polish Airlines did not allow Tu-104 planes, which could only land at Okęcie, to be squeezed into it. Czechoslovakia bought these planes.
Looking ahead, we will mention that the improved Kolesow RD-36-51A engines mounted on the next version of the Tu-144 D did not improve the situation much. The result was a slightly greater range. This variety entered service in April 1978. According to the designers, the plane was to take 121 passengers, fly at a speed of 2.35 Ma and have a range of 6,500 kilometers. In one of the experimental flights, the plane reached the speed of 2 587 km / h, which is a record so far for a passenger plane.
Written by Karol Placha Hetman