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Tu-104 Camel - Problems

As is well known, there are no revolutions without victims. The operation of the Tu-104 soon revealed serious shortcomings of the machine. Some 16 aircraft were lost in crashes. The safety record of the plane was very poor, but comparable to other jet airliners of its day. Tu-104 was unreliable, heavy, very unstable and poorly controlled in flight, it was inclined to swing (the Dutch roll).

Exploitation led to several incidents and crashes caused by aerodynamic shortcomings in the wing design and control effectiveness, after which some changes were applied to the airframe and navigation equipment and the pilots were instructed not to fly at altitudes over 10,000 meters. the Tu-104 was plagued by serious problems at the beginning. It had an aerodynamic design flaw which was not corrected against the advice of the test-pilots. After two crashes the designers accepted, that the first series of the Tu-104 could get into a deep stall as it was called.

The pilots noted that the liner was unstable in flight, heavy, prone to swinging - the so-called "Dutch rolll". But the most terrible phenomenon encountered by Tu-104 crews was "pick-up". When "picking up" the airplane within a few seconds promptly gained 1-2 km altitude with a large increase in the angle of attack. Then the plane loses speed and falls. In the era of the appearance of the Tu-104 "pick-up" was a phenomenon almost unknown. The experience of piston passenger aircraft flying at much lower altitudes could not help.

On August 15, 1958, the scheduled Tu-104 crashed near Khabarovsk. So 64 passengers and a crew member were killed. The pilots insisted that something strange was happening with the plane. Designer Tupolev strongly denied that there would be any problem whatsoever, and the tragedy was caused by the crew. There was a theory that the plane did not have enough fuel.

The situation was changed by the crash of another Tu-104, which took place 17 October 1958 in Chuvashia, near the village of Kanash. On that fateful day plane was flight Beijing and Moscow. Flying altitude was 12 km. Suddenly the plane bounced up sharply, with such a force that it soared up to two kilometers. The experienced commander of the ship Harold Kuznetsov, who encountered the "pick-up", struggled to save the aircraft until the last. But he failed to prevent the catastrophe in which he himself and 79 others died. The plane went into a steep unmanageable nosedive. At supersonic speeds, the plane sped toward the ground. The last words of the commander were: "Good-bye. Destroyed." However, the fact that Kuznetsov conveyed to the ground information on what was happening allowed the designers to understand the cause of the tragedy.

Kuznetsov transmitted information which was of great value, as all previous accidents had remained unsolved. None of the investigations carried out by the management CAF, Air Force, Municipal Institute, also of Tupolev, failed to shed light on what happened. It had been put forward a lot of guesswork: techno failure, deficiencies in the design, bad weather conditions, crew errors, etc.

Later, during the playback of the flight, the designers managed to find its characteristics: the width of the air flow was approximately 2 km in length about 13, thickness about 6 km. With all this speed it was close to 300 kilometers per hour. It was necessary to find a way to deal with such unsafe natural phenomenon. As a result, the maximum flying height was lowered, modernization of the design, development of new methods of centering machines, but all the same the problem was never solved.

The Tu-104 hit the center of a vertical stream of air 13 km long, 2 km wide and 6 km thick. The speed of air in the stream was approaching 300 kilometers per hour. The designers of the first civilian jets simply did not know of existence of such turbulence at high altitudes, and therefore did not take them into account. The Tu-104 lacked stability and height controls to combat such a threat.

The existence of the jet stream may have been first detected in the 1920s by Japanese meteorologist Wasaburo Ooishi. From a site near Mount Fuji, he tracked pilot balloons, also known as pibals (balloons used to determine upper level winds using a theodolite and the balloon''s known ascension rate due to its internal gas), as they rose into the atmosphere. Ooishi''s work largely went unnoticed outside of Japan. American pilot Wiley Post, the first man to fly around the world solo in 1933, is often given some credit for discovery of the jet stream. Post invented a pressurized suit that let him fly above 6,200 metres (20,000 ft). In the year before his death, Post made several attempts at a high-altitude transcontinental flight, and noticed that at times his ground speed greatly exceeded his air speed.

Strong winds in the upper troposphere were measured regularly in the 1930's by early versions of radiosonde balloons. The word "Strahlstrmung", meaning jet stream, was first used by the German meteorologist Seilkopf in 1939. But the phenomenon was not properly appreciated by the English until 1943, when a flight of their bombers ran out of fuel over occupied France against a wind of 54 m/s, and by the Americans not until late 1944, when their B-29 bombers faced extreme winds over Japan, where the winter jet stream is usually stronger over Europe.

Carl-Gustaf Rossby, featured on the Dec. 17, 1956 cover of Time magazine, was the key meteorologist advising the US Air Force. After World War II, under the intense prodding and flow of ideas from Rossby, most of the basic concepts of the jet stream and its perturbations were developed. The jet stream ideas were published under the authorship of "Staff Members" in 1947 in the Bulletin of the American Meteorological Society, and Rossby's theories appeared in the same volume under his own name.

Temperature and wind vary greatly in the vicinity of the tropopause affecting efficiency, comfort, and safety of flight. Maximum winds generally occur at levels near the tropopause. These strong winds create narrow zones of wind shear which often generate hazardous turbulence. The tropopause is a thin layer forming the boundary between the troposphere and stratosphere. The height of the tropopause varies from about 65,000 feet over the Equator to 20,000 feet or lower over the poles.

Meandering around the planet like a rollicking roller coaster in the sky, the Northern Hemisphere's polar jet stream is a fast-moving belt of westerly winds that traverses the lower layers of the atmosphere. The jet is created by the convergence of cold air masses descending from the Arctic and rising warm air from the tropics. The jet streams are usually thousands of miles long, a few hundred miles wide, and just a few miles thick. These currents of air situate themselves at the boundaries between warmer air and much colder air.

Clear air turbulence (CAT) implies turbulence devoid of clouds. However, the term is used for high level wind shear turbulence, even when in cirrus clouds. Even in the absence of a well-defined jet stream, CAT often is experienced in wind shears associated with sharply curved contours of strong lows, troughs, and ridges aloft, and in areas of strong, cold or warm air advection. CAT can be encountered where there seems to be no reason for its occurrence. Strong winds may carry a turbulent volume of air away from its source region.

The design of the Tu-104 was modified, which made it possible to exclude the repetition of such a tragedy. In addition, the restriction on the flight levels for the Tu-104 was introduced, which from now on should not exceed 9000 meters.

The Tu-104 continued in Aeroflot service through the 1960s and 1970s. Some 16 aircraft were lost in crashes (some due to hijackings/bombings). The safety record was comparable to other early jet airliners of its day, but was poor compared to modern airliners. Aeroflot retired the Tu-104 from civil service in March 1979 following a fatal accident at Moscow. Following this, several aircraft were transferred to the Soviet military, which used them as staff transports and to train cosmonauts in zero gravity. However, after a Tu-104 crash in February 1981 killed 52 people (17 of whom were senior army and naval staff), the type was permanently removed from service.




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