The TU-110 was a TU-104 version designed for four AL-7P turbojet engines instead of two RD-3M engines installed on TU-104. The aircraft was specially designed to comply with international requirements in view of possible mass export of the aircraft outside the USSR and the CMEA countries. For passenger aircraft of the Tu-104 class, international reliability requirements were very stringent: in particular, it was required that if an aircraft is used on routes lying above water areas, it should have a power unit consisting of at least four engines.
At the time, the risks associated with longer flights were accepted as a function of the number of engines on an airplane and were based on the reliability of engines. As engine reliabilities increased during the decades since the 1950s, there had been increasing pressure from the airline industry to recognize technological advances and allow two-engine airplanes to fly farther from airports.
In the 1980s US Federal Aviation Administration (FAA), advisory circulars introduced the term “ETOPS” for these extended operations [ExTended OPerationS, otherwise known as Engines Turn Or Passengers Swim]. Under this guidance, ETOPS operations for two-engine airplanes were permitted to fly up to 180 minutes from an airport sufficient to accommodate a landing, provided certain criteria are met. As a result of the FAA's ETOPS programs, two-engine airplane operators can fly over most of the world other than the South Polar Region, a small section in the South Pacific, and the North Polar area under certain winter weather conditions.
Extended operations, or ETOPS, for long-range international travel provide many benefits related to savings in time, fuel, and operational efficiencies. However, there are unique safety concerns associated with these operations. When one travels great distances from airports, the safety of these operations depends on the risk of critical loss of engine thrust, additional system failures during a diversion for any cause, the distance from an adequate airport used in a diversion, and the conditions encountered upon arrival at the diversion airport.
Operations under these programs have been highly successful. Although two-engine ETOPS have increased worldwide from less than 1,000 per month in 1985 to over 1,000 per day in 2004, engine reliability, as measured by the in-flight shutdown rate (IFSD rate), improved to a point that was better than one-half the rates experienced in the 1980s.
The Tu-110, a mid-range passenger aircraft, was first flown on March 11, 1957 by test pilot D.V. Zyuzin. This four-engine passenger aircraft that was a straight-forward adaptation of the Tu-104 design. It was a only modest improvement over the Tu-104, and just a few examples were built. This modification was an atempt to improve the Tu-104's reliability together with increase of maximum takeoff weight and range. A total of either three or four Tu-110s were built and later they were converted into Tu-110Bs by replacement of AL-7P engines to D-20P. These machines were primarily used as flying laboratories for testing of new engines for Tu-124 and aircraft radars.
After the beginning of the factory tests of the prototype Tu-104 in the design bureau, it was decided to design a version of this aircraft for an alternative power unit of four turbojets of lower thrust than AM-3. To some extent, this was due to the possible prospects for the export of the aircraft outside the USSR and the CMEA countries. For passenger aircraft of the Tu-104 class, international reliability requirements were very stringent: in particular, it was required that if the aircraft is used on routes running over water areas, then it should have a power unit consisting of at least four engines.
The proposal of the Design Bureau was supported by the Government, and on August 12, 1955, USSR Council of Ministers Decree No. 1511-846 issued, according to which the design bureau was to design and build a passenger aircraft with four TRDs of the AL-7 type on the basis of the Tu-104. The aircraft was to have flight and technical data close to the characteristics of the Tu-104.
Work on the design bureau for the new Tu-104 modification, which received the designation "110" (Tu-110) for the design bureau, began at the end of June 1955 and basically amounted to redesigning the price of the trolley part of the wing, taking into account the placement of four TR-engines of the AL-7P type (modification of the serial AL-7 with a thrust of 6500-6700 kg with an increased life). Unlike the Tu-104, the AL-7P engines on the PO aircraft were placed in pairs in the root parts of the wing. The center wing wing was significantly enlarged in scope, its design was changed. Due to the reduction in the diameter of the engines and the air flow through them, it was possible to abandon the separation of air flows adopted at the Tu-104. The length of the fuselage was slightly increased. The rest of the design of the aircraft did not differ from the design of the Tu-104.
In early 1957, a prototype aircraft was assembled and handed over to factory tests. On March 11, 1957, the crew, led by test pilot DVZyuzin, picked up an experienced aircraft on the first flight. The tests of the aircraft took place without any incidents, and the aircraft could be transferred to a series and produced on the GVF line and exported.
While the construction of a pilot aircraft was underway, a decision was made to implement the Tu-110 on the GVF lines and to deploy its serial production in Kazan at the plant No. 22 in the 100-seat version. The aircraft receives the designation Tu-110A. In 1957, the serial production of the aircraft began. According to the plan for 1958, Plant No. 22 was to build 5 Tu-P0A aircraft. However, all ended with the release of three aircraft. The Tu-110 aircraft as a type remained unclaimed. Large deliveries abroad were not planned (only Czechoslovakia purchased 6 Tu-104A), reliability AM-3, after their debugging, suited everyone, launched in 1958 in the series in Kazan Tu-104B was designed for 100 passengers, -110 with similar data was considered impractical m.
The prototype was converted to four D-20P engines, and then under the D-20-PO with an air sampling system for the flying laboratory TU-1 YL. Three D-20s were also installed in 1960 in D-20P, where they were tested and developed according to the program for creating the Tu-124. With engines D-20P Tu-1 10A received the designation Tu-POB. In the future these machines were used as flying laboratories for testing various electronic equipment. In addition to these works in 1960, simultaneously with the beginning of work on the Tu-124A with engines in the tail of the fuselage, a similar upgrade was proposed for the Tu-110. The project received the designation Tu-110D, but unlike the Tu-124A, which became a serial Tu-134, this work was not further developed.
An institutional culture laden with the fear of failure and the avoidance of uncertainty was not exclusive to the ranks of active duty military officers. It was also endemic to the Soviet scientific and engineering community which was responsible for designing and producing weaponry for the Red Army. This was particularly true for aircraft designers. Stalin instituted severe consequences for failed designs under the guise of what he referred to as “technological discipline”. Designers routinely lost their jobs for relatively small technical missteps and endured imprisonment or even execution for more serious design failures.
Even the best Soviet scientists and engineers such as Andrei Tupolev and his contemporaries were terrorized, arrested and imprisoned in special forced-research laboratories in the 1940’s. Such conditions continued after Stalin’s death. Khrushchev incarcerated the aircraft designer Aleksandr Arkhangelskii for failing to generate a successful prototype of the Tu-110 Soviet airliner. Even into the 1980’s, mistakes in design could cause significant detriment to an engineer’s career, standard of living and social standing.
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