Kraków 2014-02-24
An outline of the history of air navigation 1960-2000.
Supersonic passenger airplanes.
Part 1.
Introduction.
In the previous chapter, "Outline of the history of air navigation 1960-1980", we presented the most important problems in the development of commercial aviation and the accompanying navigation. This period culminated in commercial passenger airliners; Boeing 707, Douglas DC-8 and Convair 880/990 which were powered by turbojet engines. The first two designs were designed to take as many passengers on board as possible. Convair 880/990, on the other hand, were advertised as the fastest passenger airliners. Two trends emerged; more passengers or faster.
Faster.
We will once again return to the Convair 990 design, in which the company focused on increasing the cruising speed. The plane took 96-121 passengers on board. The aircraft uses reinforced General Electric CJ-805-23 engines. Convair has promised greater cruising speed and non-stop flight from one coast of the US to another. A significant change to the plane was the redesign of the wings, and more precisely the profile, and the addition of four distinctive fairings. They allowed for an increase in the critical Mach resistance and a decrease in induced drag. Thanks to this, the cruising speed actually increased and the Convair 990 was the fastest commercial plane (but Ma <1).
The first flight of the Convair 990 aircraft took place on January 24, 1961. American Airlines became the main user. In the years 1961-1963. only 37 were built. During the operation, it turned out that it was impossible to safely fly from JFK to LAX with a full set of passengers. It was necessary to make a stopover. Therefore, from 1965, shipping companies began to withdraw Convair planes from their fleet.
On the threshold of a supersonic journey.
The Convair 880/990 aircraft did not achieve market success, but pointed out that the time had come to introduce supersonic aircraft to commercial aviation. Let us remember that for over 10 years, military planes have been flying at supersonic speeds. Many specialists believed that supersonic communication could begin as early as the late 1960s. Shipping companies were also interested. These views were reasonable in terms of the technical and financial feasibility. Moreover, it was a time when commercial companies changed their planes every 5 years on average. It could have been assumed that these predictions would come true.
However, the fact that military and experimental planes were flying at supersonic speeds did not mean that all problems with commercial planes were solved. Because different laws govern test flight and combat aircraft, and other commercial aircraft. A passenger plane with a full set of passengers should cover a minimum of 5,000 km, constantly maintaining the magical speed of Ma 2.0 at that time. The experimental and even military flight is very carefully prepared. The crew of the machine is trained for many months and has special suits and rescue equipment. A cruise liner is quite another. The cruises must be performed on schedule. Passengers cannot be dressed in suits, rescue parachutes and we will not put on oxygen masks. The comfort of the cabin must be equal to that of subsonic airplanes. Mainly it is about noise, vibration and shock. Also, the flight crew must have comparable working conditions to those in a subsonic plane. The take-off characteristics of such an aircraft must correspond to those present, in order not to build special, long runways. The ground handling of these machines must also be identical to previous aircraft. We should also remember that the service life of the combat aircraft is 4,000 – 8,000 hours. The commercial aircraft has a government service life of 40,000 hours. The future aircraft will also experience significant aerodynamic and thermal loads.
And finally, the most important thing; profitability. The planes were to be competitive with their predecessors. Attempts were made to ensure that the price of a ticket in a supersonic plane was equal to the price of a ticket in the first class of a subsonic plane. This, however, did not work.
We mentioned above about noise emitted by airplanes, and mainly their powerplants. A comparative study carried out at the end of the 1970s showed that the British VC-10 and Tu-104 / Tu-124 were the loudest aircraft of that period, followed by the Convair 880 and its younger brother Convair 990. Annex-16 to the Chicago Convention introduced noise emission standards for airplanes with a take-off weight of over 5,700 kg. It happened in January 1972. Three measurement points were selected; during the take-off, 650 m to the side of the runway. / RWY, on a climb 6,500 m from the start of the roll-off, during an approach to landing 2,000 m before the runway threshold. / RWY. The permissible noise was dependent on the total weight of the aircraft, but with thresholds of 40,000 kg and 280,000 kg. So the plane weighing 400,000 kg already had the same standards as the 280,000 kg. Returning to our examples, they had the following values in the respective, successive measuring points; VC-10; 113 dB, 110 dB, 115 dB. Tu-104; 110 dB, 108 dB, 113 dB. Convair 880; 109 dB, 116 dB, 106 dB. Convair 990; 108 dB, 120 dB, 111 dB.
All the companies that started building a commercial supersonic plane made the same initial assumptions at the beginning for the construction to be successful; The safety of passengers and crew at a level not lower than in the machines used so far. The aircraft will use the same port facilities and navigation systems that are currently in use. And finally, the economic aspect.What cruising speed? Cruising speed was the determining parameter for the new design. It could not occupy the Ma 1.0 – Ma 1.5 range, as these are the least favorable flight conditions due to the highest wave resistance. When this range is exceeded, two factors begin to act and become favorable. The aerodynamic efficiency of the aircraft is improving and the efficiency of turbine jet engines is increasing. In addition, the passenger must clearly benefit from reduced travel times. If the Boeing 707 plane journey across the Atlantic Ocean lasted 6 hours, then only shortening it below 3 hours is noticeable for the traveler. So the supersonic speed must greatly exceed the speed of sound.
The problems do not end with the sound barrier. Another barrier appears; thermal (thermal) barrier. It turned out that up to the speed of Ma 2.5 it is possible to use materials previously used in aviation, i.e. high-strength aluminum alloys. Above this limit, other, much more expensive materials must be used; titanium, carbon fibers, ceramics. Possibly cooling systems.
The heat barrier meant that France and the UK decided to stay at a cruising speed of Ma 2.0 and were considered the first generation. However, in the USA it was found that the materials, technologies and construction solutions used so far will make these structures obsolete in the 70s and will require their replacement. Therefore, the speed of Ma 3.0 was set as the threshold. The prestige and successes of the XB-70 and A-12 / YF-12 A designs took the top. Today (2014) we know that the Americans failed. Not because they couldn’t. Economic reasons (cost-effect) prevailed.
Lobe concept.
Already in the 50’s, aerodynamics had well-worked out wing profiles and shapes for supersonic speeds. Not only the airfoils themselves were taken into account, but also their cooperation with the fuselage, and thus; hull shape. In almost all concepts, the main lobe is close to a triangular (delta) shape, with a highly studied leading edge, geometric and aerodynamic design. With poor or very extensive mechanization.
Tail concept.
Should I use a horizontal tail or not? It depended on how much the center of pressure moved backwards and away from the center of gravity. The greater the movement of the center of pressure, the more rational it was to use the rear horizontal tail. It was already known and used to balance an aircraft by pumping fuel. But with exceptionally long hulls, this might not be enough. There were ideas to place the horizontal tail in the front part or to use only an additional small front panel. The advantages of the duck system (or a similar one) were known from the beginning of aviation. However, this system has problems with stability. The problem was solved by the fly-by-wrie system, but it was not worked on at that time (it was only 70 years old).
Concorde.
Work on the supersonic plane in the UK, which would become the Concorde in the future, took place in the first half of 50 years. Much experience has been gathered by studying the experimental F.D.2 airplane. It was then concluded that, as in the 40-year period, a special committee should be established that would join all the efforts. The committee was formed in 1955 and named the Supersonic Transport Aircraft Committee. In 1959, the first report was published. The report identifies the aircraft as SST (Supersonic Transport); passenger, long-range, Ma 2 speed. Airframe layout – pure delta.
In 1960, the project was handled by BAC in the Bristol branch, and the design was designated BAC type 223. The first user was to be the RAF, i.e. military aviation.
Similar work was carried out in France. In 1956, the program was codenamed ATS (Avion de Transport Supersonique). In 1959, three companies; Sud Aviation, Nord Aviation, AM Dassault, began developing the named aircraft in 1961; Super Caravelle.
For economic reasons, both countries joined their efforts on October 26, 1962, signing an agreement on the joint construction of the aircraft, which was called Concorde (concord -goda). The first flight was made on March 2, 1969. On January 21, 1976, the plane began passenger flights on the Paris-Rio de Janeiro (France) and London-Bahrain (UK) routes. Let us remember that these were the routes of vital interests of both countries (France to South America, and England to the Middle and Far East). In the period 1973-1979, the plane was built serially. A total of 20 machines were built.
Basic data; span 25.56 m, length 62.10 m, height 11.40 m. bearing area 358.25 m, empty weight 78 700 kg, max weight 185 000 kg, fuel quantity 119 786 liters, lifting capacity 12 700 kg. Max speed 2.04 Ma. Take-off speed 397 km / h, landing speed 300 km / h, ceiling 18 290 m, climb speed 25.5 m / s, standard range 5 110 km, max range 6 580. Take-off 3 410 m. Landing 2 220 m.
Tupolew Tu-144.
The origins of the Tu-144 program are unknown. In all likelihood, CCCP intelligence captured the Concorde aircraft in France around 1964. The Kremlin decided to copy the construction. The program received the designation Tu-144, which was supposed 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 was not adopted, limited only to the leading edge running 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. It was similar with the engines marked Kuznetsov NK-144. In fact, these were engines used to propel bomber aircraft with enhanced afterburning. According to propaganda materials, the engine was to develop a thrust of 4 x 20,000 kG. In fact, they had a thrust of 4 x 127.48 kN (4 x 13,000 kG), and with an afterburning 4 x 174.55 kN (4 x 17,500 kG). 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. They did not have the appropriate machinery.
The fact is that the Tu-144 was flown on December 31, 1968, that is in front of the Concorde plane, which the Kremlin authorities emphasized at every step. On June 5, 1969, the plane reached a speed of 1 Ma, with an altitude of 11,000 m, and on May 26, 1970, speed 2 Ma, with an altitude of 16,300 m. It was carefully concealed that the crews were using oxygen masks all the time.
The rush meant that the machine was plagued by numerous faults and serious failures. This was the cause of many forced landings, which in the official press were translated into courtesy visits. This was the case, for example, in 1971 at the Okęcie Airport. Breaking wings were serious failures, and as a consequence fuel tanks became unsealed and leaked. On June 3, 1973, one of the airplane prototypes crashed during the Paris Air Show. 6 people died on board and 8 people on the ground. To this day, no specific causes of this occurrence are known. After the accident, it was rumored that the plane flew into a plume of exhaust gases from the French fighter that photographed it. However, subsequent research points to a possible problem in the control system that was incorrectly reprogrammed at the last minute. There is also a possible error of the crew that overestimated the climb. In 1978, there was a second catastrophe in which two people were killed.
But the pressure to put the aircraft into service was enormous. Tu-144 S from December 26, 1975, began regular cargo flights on the route Moscow – Almaty, carrying cargo and mail. Passenger flights began in December 1977 and it was only a few voyages. But the supersonic flights were fiction. Yes, the plane reached the speed of 2.35 Ma, but only with the afterburners turned on. After they were turned off, the speed dropped to 1.25 Ma and the theory of fast transport was crushed.
In 1978, one of the variants received new Kolesov turbojets. But the only effect was the greater range of the machine. The unreliability and failure rate of these machines, the enormous flight costs associated with very high fuel consumption and a large amount of ground service, meant that the machines were decommissioned quite quickly and without publicity. In total, Tu-144 aircraft performed only 55 scheduled passenger flights, 102 commercial scheduled flights in general. In total, 16 aircraft were produced. It is difficult to talk about varieties, because some of the copies have been rebuilt several times. Although the S and D versions and one LL used in the 90-years for a joint program with NASA are given. Interestingly, American pilots never participated in the flights of these aircraft.
Written by Karol Placha Hetman