Tupolev Jetliners

v2.2.4 / 01 jun 20 / greg goebel

* The Soviet experimental design bureau (OKB in its Russian acronym) headed by Andrei Tupolev is best known for its series of bombers, but it also developed a series of jet airliners, including the "Tu-104", "Tu-124", "Tu-134", "Tu-154", and "Tu-204". This document provides a history and description of these aircraft.

Tupolev Tu-154M

[1] TUPOLEV TU-104 & TU-124
[2] TUPOLEV TU-134
[3] TUPOLEV TU-154

[1] TUPOLEV TU-104 & TU-124

* In the early 1950s, the Tupolev OKB developed the Tu-16 "Badger" bomber, a swept-wing design powered by twin Mikulin RD-3 turbojet engines. In parallel with the design effort on the bomber, the organization also worked on a jetliner derivative.

Formal work on the jetliner began in the spring of 1953, with the initial flight of the prototype of the "Tu-104", as the machine was designated, on 17 June 1955, with Y.I. Alashayev at the controls. The Tu-104 went into service with the Soviet state airline Aeroflot in 1956, with the new, advanced jetliner causing a stir in the West when it arrived in foreign capitals with Soviet bigwigs on board. The type was assigned the unflattering NATO reporting name of "Camel".

The Tu-104 used wings and tail derived from the Tu-16, fitted to an airliner fuselage; there were some minor detail differences in the Tu-104's flight surfaces relative to the Tu-16. Like the Tu-16, the Tu-104 featured low-mounted swept wings and twin RD-3 engines, with 93.2 kN (9,500 kgp / 20,950 lbf) thrust each, in nacelles next to the fuselage, and four-wheel main landing gear assemblies, using 2x2 bogies, in pods on the wings -- the landing gear wing pod scheme being something of a Tupolev trademark.

The Tu-104's pressurized fuselage was 3.4 meters (11 feet 2 inches) in diameter, compared to 2.9 meters (9 feet 6 inches) for the Tu-16. The Tu-104 was flown by a crew of five including pilot, copilot, radio operator, flight engineer, and navigator. The aircraft featured navigation radar in a fairing under the nose and nose glazing for the navigator, a distinctive feature found on many Soviet airliners.

Initial accommodations were for 50 passengers. Passenger headspace was limited where the wing spars went across the fuselage, and so there was a galley separating front and back seating sections at that point. In the initial production version, there were two "first class" sections forward of the wing, with six passengers in the forward section and eight in the second, both featuring tables and other niceties. There was another eight-passenger section behind the galley, followed by "coach" seating for 28, in seven rows four seats across.

There was a toilet forward and two toilets aft. Apparently the accommodations were spiffy, particularly by Soviet standards, with brass and mahogany fittings; obviously, the Tu-104 was seen as "showpiece" for Soviet technology and industry. It did have a longer take-off run than the Soviet propliners then in service, requiring the extension of runways at a large number of airports in the USSR to handle the new machine, but that would have had to be done in any case as aircraft performance improved.

Uprating the RD-3 engine increased the gross take-off weight, leading to the "Tu-104A", which was introduced to service in 1957 and could carry 70 passengers, with five-abreast seating. A Tu-104A set a series of altitude and speed with load records in 1957.

Development of the "RD-3M" engine, with 85.3 kN (8,700 kgp / 19,180 lbf) thrust, led to definitive "Tu-104B" variant, which was introduced in 1959. It featured a 1.21 meter (4 foot) fuselage stretch, wings with wider chord and bigger flaps to handle the weight increase, various general improvements, and accommodations for 100 passengers. The early compartmentalized scheme gave way to straight-through accommodations of 30 passengers before the wing, 15 passengers in the center section, and 55 behind. The Tu-104B also set a series of altitude and speed with load records in 1959.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                34.54 meters        113 feet 4 inches
   wing area               183.50 sq_meters    1,975 sq_feet   
   length                  40.06 meters        131 feet 5 inches
   height                  11.90 meters        39 feet

   empty weight            41,600 kilograms    91,710 pounds
   MTO weight              76,000 kilograms    167,550 pounds

   max speed at altitude   950 KPH             590 MPH / 515 KT
   service ceiling         11,500 meters       37,750 feet
   range                   3,100 kilometers    1,925 MI / 1,675 NMI
   _____________________   _________________   _______________________

A number of Tu-104As were converted to a 100-passenger configuration and redesignated "Tu-104V". That sounds a little cramped, and not surprisingly there was a "Tu-104D" conversion that had more reasonable accommodations for 85 passengers. There was also a single "Tu-104E", which was a Tu-104B tuned for record-breaking flights. A number of Tu-104s of various types were used for special applications, including weather research, and as a "vomit comet" to perform dives that would allow Soviet cosmonauts to experience short periods of zero gee before going into space. Two Tu-104s were fitted with YeN radar to serve as trainers for the Tu-16K-10 "Badger-C" bomber and were designated "Tu-104Sh". They were later upgraded with radar and systems for the Tu-22M "Backfire" bomber, and redesignated "Tu-104Sh-2".

The last of about 200 Tu-104s was rolled out in 1960. The only export user was CSA of Czechoslovakia, which bought six Tu-104As. Most Tu-104s in Aeroflot service were updated in the late 1960s to handle 104 or 115 passengers, which suggests that the nice trim seen in early production had been dispensed with. The type was finally retired from Aeroflot service in 1981. While crude by modern standards, the Tu-104 was leading-edge at the time of its introduction, and in fact it was the second jetliner to go into full service, following Britain's much less successful de Havilland Comet. Although noisy and fuel-hungry in hindsight, the Tu-104 also had an excellent serviceability and safety record.

Tupolev Tu-105 Camel & Tu-124 Cookpot

* The Tu-104 had seemed like such a good idea that it was followed in production by a scaled-down derivative, the "Tu-124", which had a very similar general arrangement -- so similar that the two types could be difficult to tell apart -- but length and span only about 75% of the Tu-104, and weight only about half. There was no substantial parts commonality between the two designs. Initial flight of the prototype was in June 1960, with introduction to service in 1962.

The Tu-124 was powered by twin Soloviev D-20P turbofans with 52.9 kN (5,400 kgp / 11,900 lbf) thrust each. The Tu-124 had slightly improved aerodynamics over the Tu-104, giving a sleeker look. The fuselage width was 2.9 meters (9 feet 6 inches), like that of the Tu-16. The Tu-124 was fitted with 44 seats, which was increased to 55 on the "Tu-124V". There were also VIP transport variants, including the "Tu-124K", with 36 seats, and the "Tu-124K2", with 22 seats. About a hundred Tu-124s of all types were built, to be operated on short-haul routes through the 1960s and 1970s. It was assigned the quirky NATO reporting name of "Cookpot".

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                25.55 meters        83 feet 10 inches
   wing area               119 sq_meters       1,281 sq_feet   
   length                  30.58 meters        100 feet 4 inches
   height                  8.08 meters         26 feet 6 inches

   empty weight            22,500 kilograms    49,600 pounds
   MTO weight              38,000 kilograms    83,755 pounds

   max speed at altitude   970 KPH             605 MPH / 525 KT
   service ceiling         15,000 meters       49,200 feet
   range                   2,100 kilometers    1,305 MI / 1,135 NMI
   _____________________   _________________   _______________________

A few Tu-124s served in the Red military as "Tu-124Sh" navigation trainers. Three were supplied to the Czech CSA airline, and two to the East German Interflug airline. A handful were also sold to the Iraqi and Indian air forces as VIP transports. Like its bigger sister, the Tu-124 obtained a reputation for serviceability and safety.

* There were several other branches from the Tu-104 line besides the Tu-124, none of which went anywhere. There was consideration of a "Tu-107" military cargolifter based on the Tu-104, with a production Tu-104 converted to a prototype, which performed trials from 1958. The Tu-107 was generally similar to the Tu-104 except for a reduced number of windows, a tail turret with twin AM-23 23-millimeter cannons, and a tail loading ramp. It could carry up to 100 troops, 70 paratroops, or one or two combat vehicles. It was basically limited by the fact that the tail loading ramp couldn't be opened in flight and paradropping heavy loads was impossible; the Tu-107 did not go into production.

Tupolev Tu-110 & Tu-118

A "Tu-110" was also developed roughly in parallel with the Tu-104, being much the same except for fit of four smaller AL-5 turbojets, with 53.9 kN (5,500 kgp / 12,125 lbf) thrust each, instead of the two big RD-3s. Although the Tu-110 apparently had some advantages over the Tu-104, the four engines in particular providing greater flight safety, they weren't significant enough to encourage production; the sole Tu-110 prototype was turned over to the Red Air Force, apparently for use as a VIP transport. A "Tu-118" with four TV-2F or NK-8 turboprops, in the 4,475 to 5,970 ekW (6,000 to 8,000 EHP) range and driving contra-rotating propellers, was considered to extend range, but not built.


[2] TUPOLEV TU-134

* Tupolev OKB engineers felt they could improve on the Tu-124, and after considering various options a team under Leonid Selyakov came up with a successor to the Tu-124, moving the twin engines mounted in the wingroots to the tail, and fitting a tee tail. The new machine was originally designated the "Tu-124A" -- apparently it leveraged off Tu-124 assemblies -- with six development aircraft built, the first flying in December 1963. Production began in 1964 at a factory in Kharkov, though it wasn't until September 1967 that Aeroflot, the Soviet state airline, put the aircraft into full commercial service as the "Tu-134". NATO assigned the type the eccentric reporting name of "Crusty".

The Tu-134 had a general configuration similar to that of the US Douglas DC-9. The production aircraft was powered by twin rear-mounted Soloviev D30 low-bypass turbofans with 66.7 kN (6,800 kgp / 14,990 lbf) thrust each; the initial Tu-124A prototypes had featured Soloviev D20P turbofans, with about 20% less thrust. There were three fuel tanks in each wing, providing a total fuel load of 16,500 liters (4,353 US gallons).

The two-spar wings featured a sweepback of 35% at wing midline, an anhedral droop of 1.3 degrees, four-section flaps and two-section ailerons, with spoilers / lift dumpers on top of the wing. The tailplane had conventional elevators, but featured adjustable incidence for pitch trim. There was a airbrake under the fuselage, used for reducing speed on approach. All flight controls were manual except for the tailplane incidence adjustment, which was electrically actuated.

The nose landing gear featured twin wheels while the main gear assemblies featured four wheels. All landing gear assemblies retracted backwards, each main gear assembly being stowed in the traditional Tupolev fashion in a pod at the rear of the wing. Disk anti-skid brakes were fitted. The tailplane featured an electrical de-icing system, while the wings, tailfin, and engine inlets were de-iced by engine bleed air. The windscreen used both hot air and electrical de-icing.

Flightcrew included pilot, copilot, and navigator, plus two stewardesses, with nose glazing to allow the navigator to make observations, and weather radar mounted in a radome under the nose. Other avionics were basic but state-of-the-art -- radios, landing aids, navigation aids, and identification transponder.

Tupolev Tu-134

The load capacity was 72 passengers in a single-class configuration, sitting four abreast; 64 passengers could be accommodated in a two-class configuration, with 16 first class passengers in the forward compartment, 20 economy in the middle compartment, and 28 economy in the rear compartment. There were two galleys and two toilets. There were no underfloor cargo holds, with luggage stowed behind the pilot's compartment and at the rear. There was only a single passenger door, on the left forward fuselage, with cargo doors for each cargo compartment on the right, and an emergency exit over each wing.

   TUPOLEV TU-134:
   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                29 meters           95 feet 2 inches
   wing area               127.3 sq_meters     1,370 sq_feet   
   length                  34.35 meters        112 feet 8 inches
   height                  9.02 meters         29 feet 7 inches

   empty weight            27,500 kilograms    60,630 pounds
   MTO weight              44,500 kilograms    98,105 pounds

   max cruise speed        900 KPH             560 MPH / 485 KT
   efficient cruise speed  750 KPH             465 MPH / 405 KT
   service ceiling         12,110 meters       39,730 feet
   range, 7 tonne load     2,400 kilometers    1,490 MI / 1,295 NMI
   range, 3 tonne load     3,500 kilometers    2,175 MI / 1,890 NMI
   _____________________   _________________   _______________________

The Tu-134 featured various upgrades in service, most significantly fit of an auxiliary power unit (APU) turbine engine for main engine starting (the APU output driving electrical starters) and ground power. Clamshell thrust reversers were then added, with the modified engines designated D30 Series II. Avionics were continuously updated.

* The initial production Tu-134 was followed in 1970 by the "Tu-134A", which had a fuselage stretch of 2.1 meters (6 feet 11 inches) to 37.05 meters (121 feet 7 inches); the APU introduced on upgraded Tu-134s; and more powerful D32 / D30 Series III turbofans providing 69.4 kN (7,080 kgp / 15,610 lbf) thrust each, along with improved "hot and high" performance. A prominent recognition feature was a needle-like VHF radio antenna mounted in the front of the tee-tail bullet fairing.

Tupolev Tu-134 / Tu-134A

Load was increased to 84 passengers in a single-class configuration, or 12 first class and 54 economy class passengers, with expanded baggage accommodation. Empty weight was raised by 1,550 kilograms (3,420 pounds) to 27,500 kilograms (60,640 pounds). The landing gear and wings were reinforced to handle the higher weight. Later production eliminated the nose glazing, which was seen as "draggy", replacing it with an improved radar system. Some older production was also refitted with the new nose.

* Final production included the "Tu-134A-3", with new lightweight seats to permit a single-class load of 96 passengers; and then the "Tu-134B", with modernized cockpit accommodations that eliminated the navigator position. Sources also mention a few other minor variants, notably military crew trainers -- including the "Tu-134BSh", which was fitted with the nose of a Tu-22M "Backfire" bomber.

Production ended in 1978. Sources give the number built as about 800. Most Tu-134s served with Aeroflot, though it was popular with the airlines of Eastern European nations and some Soviet client states as well. It was regarded as fairly stereotypical Soviet hardware: heavy, with poorer fuel economy and passenger load than, say, a DC-9, but very sturdy and easy to keep flying. Only a handful are still in service.


[3] TUPOLEV TU-154

* The Tu-104, the first production Soviet jetliner, led to the downscaled Tu-124, which led in turn to the Tu-134. The Tu-104 itself led to a more modern replacement, the "Tu-154".

The Tu-154's design specs included the ability to operate off of rough or short airstrips and good altitude performance, to allow it to fly above most Soviet air traffic. A Tupolev engineering team, originally under S.M. Yeger and later under Dmitriy Markov, developed an aircraft with a general resemblance to the Boeing 727, featuring low-mounted swept wings, a swept tee tail, and three engines -- Kuznetsov NK-8-2 low-bypass turbofans providing 93.2 kN (9,500 kgp / 20,950 lbf) thrust each, with one mounted in the base of the tail and one mounted on each side of the rear fuselage. An APU was provided for engine starting and ground power.

The Tu-154 differed significantly from the Boeing design in retaining the distinctive Tupolev approach of mounting the main gear in wing pods. Each wing featured three spars, five-section leading-edge slats, two-section triple slotted flaps, one-piece ailerons, and an array of spoilers / lift dumpers / airbrakes on top. Wing, tail, and engine inlet de-icing was performed using engine bleed air, while the slats were electrically de-iced. The steerable nose gear featured dual wheels. Each main gear assembly featured six wheels, mounted on a bogie in three rows of two wheels. All landing gear assemblies retracted hydraulically to the rear. Flight crew consisted of pilot, copilot, navigator, flight engineer, and at least two stewardesses. Typical single-class seating was 128, six abreast, or 146 in a high density configuration.

Initial flight of the Tu-154 was on 4 October 1968, with initial delivery of a production machine to Aeroflot in early 1971 and introduction to service a year later. It was given the NATO reporting name of "Careless".

   TUPOLEV TU-154:
   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                37.55 meters        123 feet 3 inches
   wing area               201.5 sq_meters     2,168 sq_feet   
   length                  47.9 meters         157 feet 2 inches
   height                  11.4 meters         37 feet 5 inches

   empty weight            43,500 kilograms    95,900 pounds
   MTO weight              90,000 kilograms    198,415 pounds

   max cruise speed        975 KPH             605 MPH / 525 KT
   efficient cruise speed  900 KPH             560 MPH / 485 KT
   service ceiling         12,110 meters       39,730 feet
   range, max payload      3,460 kilometers    2,150 MI / 1,870 NMI
   range, max fuel         5,280 kilometers    3,280 MI / 2,850 NMI
   _____________________   _________________   _______________________

The initial series Tu-154 was followed in 1974 by the "Tu-154A". It was difficult to distinguish from the Tu-154, but featured uprated NK-8-2U engines providing 103 kN (10.5 kgp / 23,150 lbf) thrust each, permitting an increase in take-off weight and, with the addition of new emergency escape doors, a maximum passenger load of 168. There were various improvements in systems. A new fuel tank was added in the center section, but oddly it couldn't be used in flight; the fuel was transferred on the ground to other aircraft fuel tanks.

Tupolev Tu-154

The Tu-154A was followed in turn in 1977 by the "Tu-154B" variant, which quickly evolved to the "Tu-154B-2". The major change was still more max take-off weight, allowing (with more emergency exits) a passenger load of 180. The center section fuel tank was integrated into the rest of the aircraft fuel system, and a number of small changes were implemented. In the early 1980s a "Tu-154C" air freighter was introduced, such machines amounting to conversions of Tu-154A/B aircraft with a cargo door on the forward left fuselage and cargo handling facilities in the cargo hold. Max cargo load was 20 tonnes (22 tons).

* The first series Tu-154s led in 1981 to the second-series "Tu-154M", which featured much more economical, quieter, and reliable Soloviev (later AviaDvigatel) D-30KU-154-II turbofans -- through the max thrust provided by the new engines was about the same as that of the NK-8-2U, 104 kN (10,600 kgp / 23,380 lbf) each. The engine intakes had to be expanded to handle the greater airflow. The Tu-154M featured about 20% better range and an increase in max take-off weight of about 10,000 kilograms (22,000 pounds) relative to the baseline Tu-154. Maximum passenger capacity was 180 in a six-abreast configuration.

Tupolev Tu-154M

About 850 Tu-154s were built in all, with over 70% of them being Tu-154Ms. Again, most were obtained by Aeroflot, but many were also provided to the airlines of Eastern European and Soviet client states. China obtained a number them, with at least four modified to a special missions / surveillance configuration with large belly fairings fore and aft of the wings -- these machines being operated by the Chinese People's Liberation Army Air Force. The Tu-154 was regarded as clearly less economical to operate than a Boeing 737, but much sturdier and easier to maintain. The Tu-154 remains in service, but it is approaching the end of its days.



* By the last days of the Soviet Union in the late 1980s, the Tupolev OKB was working on new jetliners, but the collapse of the USSR threw these programs into some confusion.

Tupolev Tu-204

Development of a successor to the Tu-154, as well as the Ilyushin Il-62 jetliner, began in the 1980s, with the first flight of the "Tu-204" on 2 January 1989. It was a modern narrow-body twinjet airliner with a close resemblance to the Boeing 757. It featured a "supercritical" wing with a sweep of 28 degrees and winglets; Soloviev (now Aviadvigatel) PS90 high-bypass turbofans, with 158.3 kN (16,135 kgp / 35,580 lbf) thrust each; a triple-redundant "fly-by-wire" digital flight control system with analog backup; and a "glass cockpit" with six displays.

The airframe consisted of almost a fifth by weight of composite materials, and included both titanium and lithium-aluminum alloy elements. The steerable nose gear had twin wheels, while the main gear assemblies had four wheels. The landing gear featured antiskid disk brakes and was hydraulically actuated, the nose gear retracting forward, the main gear retracting inward into the fuselage -- the Tu-204 did not use the trademark Tupolev wing-pod scheme.

Crew included pilot, copilot, and an optional flight engineer, as well as at least two flight attendants. Seating was six-abreast, with 210 passengers in a high-density configuration and various mixed configurations, such as 24 first class and 159 economy class seats. There were three galleys and three toilets.

   TUPOLEV TU-204:
   _____________________   _________________   _______________________

   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                41.80 meters        137 feet 2 inches
   wing area               182.4 sq_meters     1,963 sq_feet   
   length                  46.1 meters         151 feet 3 inches
   height                  13.9 meters         45 feet 5 inches

   empty weight            58,300 kilograms    128,530 pounds
   MTO weight              94,600 kilograms    208,550 pounds

   cruise speed            850 KPH             530 MPH / 460 KT
   range, max payload      2,430 kilometers    1,510 MI / 1,310 NMI
   _____________________   _________________   _______________________

A number of variants were introduced or proposed:

Several special-mission machines have been produced:

To appeal to customers who were interested in Western jetliners, the Tupolev organization built a "Tu-204-120" with Westernized (Honeywell) avionics and Rolls-Royce RB211-535 powerplants. The first flew on 14 August 1992. A "combi" freighter variant, the "Tu-120-100C", was built as well, to be followed by the "Tu-120-CE" with higher MTO. A number of Rolls-Royce powered Tu-204s were sold to Egypt and users in Europe.

Tupolev Tu-204-300

A "Tu-204SM", a modernized derivative of the Tu-204, first flew in late 2010. It featured generally modernized avionics, including a new cockpit and flight computer; much-improved and much more reliable PS-90A2 engines; a new APU; and a new interior, featuring LED lighting.

Total production quantities of the Tu-204 series are unclear, but appear to be modest, about four prototypes and 38 production machines by 2006. Sources give the impression of listing more Tu-204 variants than the actual number of Tu-204s built. It appears that the days of the Tu-204 are numbered, the new "Irkut MC-21" twinjet being slated to replace it.

* While the Tu-204 series was a replacement for the Tu-154, the Tupolev organization also developed a "shortened" derivative of the Tu-204, the "Tu-334", as a replacement for the Tu-134. The end result didn't have much resemblance to the Tu-204, in fact resembling a Fokker 70/100 jetliner, with twin rear-mounted turbofan engines, a tee tail, and winglets.

Although the development program was initiated in 1986, it was derailed by the collapse of the USSR, with first prototype finally performing its initial flight on 8 February 1999; a second prototype was planned at the outset, but it never actually flew. Two more prototypes and an initial batch of "Tu-334-100" production machines were supposedly to follow, with the Tu-334-100 powered by twin ZMKB Progress D436T1 high-bypass turbofans with 73.6kN (7,500 kgp / 16,535 lbf) thrust each.

Tupolev Tu-334

The Tu-334-100 featured fly-by-wire controls, a crew of two or three, and a maximum capacity of 102 passengers in a single-class configuration, six abreast -- or 72 in a two-class configuration, including 12 first-class passengers seated four abreast and 60 economy passengers seated six abreast.

   TUPOLEV TU-334:
   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                29.77 meters        97 feet 8 inches
   wing area               83.2 sq_meters      896 sq_feet   
   length                  31.26 meters        102 feet 7 inches
   height                  9.38 meters         30 feet 9 inches

   empty weight            30,050 kilograms    66,250 pounds
   MTO weight              46,100 kilograms    101,630 pounds

   efficient cruise speed  820 KPH             505 MPH / 440 KT
   range, full payload     2,000 kilometers    1,240 MI / 1,080 NMI
   _____________________   _________________   _______________________

A range of configurations was considered, including stretched variants, "combi" machines, and Westernized aircraft with Rolls-Royce engines -- but as it turned out, only the two prototypes were ever built. In 2009, in the course of consolidation of the Russian aircraft industry, the decision was made to stop work on the Tu-334, to focus instead on the Sukhoi Superjet 100 and the Antonov An-148 small jetliners.



* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Sources:

Several editions of JANE'S ALL THE WORLD'S AIRCRAFT were also consulted.

Tupolev Tu-134B

* Revision history:

   v1.0.0 / 01 may 08 
   v2.0.0 / 01 jan 09 / Added Tu-104 & Tu-124.
   v2.0.1 / 01 dec 10 / Review and polish.
   v2.1.0 / 01 nov 12 / Tu-214ON and Tu-214R added, Tu-107 and Tu-118 added.
   v2.2.0 / 01 oct 14 / PLAAF special-mission Tu-154M, Tu-334 cancellation.
   v2.2.1 / 01 sep 16 / Review & polish.
   v2.2.2 / 01 sep 16 / Review & polish.
   v2.2.3 / 01 aug 18 / Review & polish.
   v2.2.4 / 01 jun 20 / Review & polish.