“144” (TU-144). First in the world supersonic passenger production aircraft

Successful building in the 50-s of supersonic combat airplanes including heavy ones, created a favorable situation to study possibilities for building supersonic passenger airplanes SST). First SST projects took their origin in the first post-war years when in the USA and in UK some hypothetical projects were proposed which technical approaches were too far from practical realization. In late 50-son both sides of “iron curtain” there appeared first prototypes and consequently production supersonic heavy airplanes of military purpose and substantially straight away on this basis leading world aircraft companies prepared projects of the SSTs of various aerodynamic schematics and arrangements. Comprehensive review of these SST projects revealed that building of effective competitive SST by upgrading of military prototype – is extremely complicated task (in contrast to the process of first jet passenger aircraft building basing on subsonic heavy combat aircraft). First supersonic combat mainly complied with requirements of relatively short supersonic flight. The SST had to ensure cruising flight at speeds corresponding to at least M=2 plus specific task of passenger transportation required significant increase in safety level of all aircraft components provided the aircraft is operated more intensively by increasing supersonic modes of flight. Step by step making analysis of all possible approaches aircraft specialists both in the USSR and in the West came to a firm opinion that economically efficient SST should be designed as a radically new type of aircraft.

TUPOLEV DB started SST designing in early 60-s. First technical proposals were mainly based on large-range bombers. Later on when activities started on TU-144 a/c S.Yeger proposed preliminary project of TU-144 powered by NK-144 engines. Besides TUPOLEV DB preliminary study of SST in the USSR was made in DB-23 named after V. Myasishev. In this DB in late 50-s some original SST projects were prepared (M-53, M-55A, M-55B and M-55V).

Early 60-s were characterized by deployment of practical activities on English-French SST “Concord” (investigation of the subject was started in 1955-1956) with cruising supersonic flight speed more than M=2 and flight range of 6000 – 6500 km carrying 120-140 passengers. Simultaneously leading aircraft USA companies basing on their view of future SST market started working on designing of much greater SST than “Concord” which was intended for transportation of 250-300 passengers at cruising speed up to M=3 for the range of 7000 – 8000 km (projects of Boeing, Lockheed, Douglas).

Analysis of conditions of existing of future SST made in the USSR regarding to the level of native aircraft manufacturing and its closest future and also regarding economical potentials of the country and Civil Aircraft Fleet demands, revealed that for the USSR the most preferable was building of the SST which was close to “Concord” by its performance data. In the course of building the Soviet SST a number of scientific tasks were put in front of our aircraft science and industry These tasks have not ever been put in front of our subsonic passenger or military supersonic aviation. first of all to ensure required SST performance data (M=2 flight for the range of up to 6500 km carrying 100-120 passengers in combination with acceptable take-off and landing data) it was necessary to provide significant improvement of aerodynamic cleanness of the aircraft during cruising flights at M=2 –2.2. Under such conditions L/D ration should be increased up to 7.5 – 8.0. It was necessary to solve stability and controllability problems of a heavy aircraft during flights within subsonic, transonic and supersonic envelopes, to elaborate practical methods for trimming aircraft under all said conditions in view of minimization of aerodynamic loss. Durable flight at the speed of M=2 was associated with strength of airframe design at increased temperatures (close to 100-120 o C). We were going to create heat resistant structural material, lubricants, sealant and also to elaborate new types of structures capable for long-term operation under cyclic aerodynamic heating. Very high requirements were established to Powerplant components: it was necessary to build powerful and economically efficient engines capable to operate steadily during supersonic flight. Also it was necessary to solve problems of controlling air intakes operated within wide range of altitudes and speeds by controlling required inlet air flow at possible less aerodynamic loss. The most efficient was to perform durable supersonic cruising flight at high altitudes. Accordingly main and component DB were put in front of the tasks of designing of principles of new air-conditioning systems and later specific components and systems ensuring passengers and crew members with comfortable conditions at high altitudes (up to 20 km) and when durable flights at significant heating of airframe components. We had to design a number of new devices and systems for automatic flight control, precision navigation when performing durable supersonic flight and also automatic landing. Necessity arose to investigate ecological features of the SST operation associated with emission of great amount of engines exhaust gases at high altitudes and their affect upon ozone layer, noise and sound wave affect upon people, animals and buildings, affect of durable flight at high altitudes upon passengers and crew members associated with solar irradiation. When designing the SST it was necessary to take into account particularity of domestic and international air transportation, existing airfields and air traffic control.

All said problems were studied comprehensively with attraction of western practice by TsAGI, TUPOLEV DB, and other DBs involved in the Program on designing of soviet SST. Official basis of the first generation SST (SST-1) building designated as TU-144 was Resolution of Council of Ministers of the USSR, 1963 and Decree of the same year. TUPOLEV DB was given a task to design and build SST with cruise flight speed of 2300-2700 km/h, operational range at supersonic speed with 80-100 passengers on the board was prescribed to be 4000-4500 km; in accelerated version with additional fuel tanks carrying 30-50 passengers – 6000-6500 km/h. Operation from I-st class airfields at normal take-off weight of 120-130 tones. In 1966-1967 we were going to build 5 TU-144 machines (two machines were intended for structural tests). In view of technical complexity of obtaining maximal flight range works were divided into two steps: at the first step operational flight range was to be 4000- 4500 km/; at the second step TU-144 a/c had to reach flight range of 6500 km. By-pass turbofans with reheat chamber was prescribed for the TU-144 a/c. DB named after N. Kuznetsov undertook creation of turbofans for the SST that were designated as NK-144 having take-off thrust of 20000 kgf and sfc equal to 1.35-1.45 kg/kgf h at cruising flight. It should be noted that the TU-144 project progress was mainly effected by a successes of engine manufacturers. This choice was not self-evident. It was more reliable and chipper and allowed flights within more wide range of altitudes and speeds in comparison with simple turbojets. Possibility to have small fuel consumption at cruising speed and consequently – ensurance of required flight range. It was not a surprise both for TUPOLEV specialists and for Ministry of Aircraft Industry. During designing of Myasischev SST there were results showing that it was quite realistic to obtain suitable supersonic flight range if to use engines with sfc not more than 1.2 kg/kgf hour. Prototype of such engine was built in the 60-s in the USSR – it was nonafterburning turbojet “16-17” (take off was 18000 kgf, sfc at cruising flight was 1.15 kg/kgf hour) which was designed in DB-16 named after P.Zubtsov. English and French designers of the “Concorde” chose an intermediate way and selected reheated turbojet Bristol “Olymp” 593 with non-high reheating and with SFC = 1.327 kg/kgf hour at afterburning (afterburning takeoff is 17200 kgf). Unfortunately works on heavy SST at Myasischev DB were terminated. Thus in early 60-s in the USSR development of powerful economically efficient nonafterburning turbofans temporarily was stopped (DB-16 was switched to solid rocket engines. As a result by the beginning of the TU-144 a/c designing the TUPOLEV DB had to undertake a technical risk by selecting NK-144 . In 1964 it was decided to resume works on economically efficient powerful nonafterburning turbojet for SST: in DB-36 under P. Kolesov they started to design RD-36-51 turbojet for TU-144 a/c with maximal take off equal to 20 000 kgf and estimated SFC of 1.23 kg/kgf h at supersonic cruising .

Chief Designer and Manager was Alexey Tupolev. Tu-144 a/c conception and future layout was originated under his leadership and with best aviation science specialists involved. Later on the TU-144 a/’c Project was managed by Y. Popov and B. Gantsevskiy. Soon the TU-144 Project became one of main and priority subjects of the DB and of the whole Ministry of Aircraft Industry for the nearest decade.

TU-144 aerodynamic layout was defined mainly by long flight range at cruising supersonic speed at required stability and controllability and prescribed take-off and landing characteristics. Basing on promised SFC of the NK-144 at the first step of designing the task was to reach Kmax=7 at cruising supersonic flight. According to economical, technological and weight aspects M=2.2 was assumed. In the course of TU-144 aerodynamic arrangement study several tens of approaches were considered. First “normal” arrangement with horizontal tail. It was rejected since such tail contributed up to 20% to total amount of aircraft drag. “Canard” arrangement was also rejected due destabilizer affect on main wing. Finally they decided in favor of low-wing arrangement – “tailless” a/c with ogival double-delta wing (the wing was defined by two triangle airfoils with strake edge sweep angle of 78o and 55o along rear basic portion) provided with four afterburning turbojets installed under the wing with vertical tail is installed along longitudinal axis and with retractable tricycle landing gear. Airframe structure was mainly made of common aluminum alloys. Wing was defined by symmetrical profiles and had complex twist in two direction: longitudinal and lateral. This resulted in the best flow about the wing at supersonic speed. Furthermore this twist contributed to improvement of longitudinal trimming under said conditions.

Entire rear edge was provided with four-pieces elevons per each half-wing. The wing has multi-spar structure with powerful skin made of continuous aluminum alloys plates, central wing and elevons were made of titanic alloys. The elevons sections were activated by two irreversible actuators. Rud was deviated by means of irreversible boosters and was defined by two separate sections. Aerodynamic arrangement of he fuselage were chosen in view of obtaining minimal drag under supersonic conditions. Aiming at this the aircraft structure was made more complicated. Characterizing feature of TU-144 a/c became sinkable , well glazed nose fuselage in front of cockpit which provided good view at large take-off and landing angles of attack inherent to the airplanes with wings of small aspect ratio. The nose fuselage could be lowered or hoisted by means of hydraulic drive. When designing the deflectable non-pressurized portion and its components we managed to preserve smooth skin in interfaces between the movable portion and pressurized and the rest fuselage surface. Engine nacelle form was mainly defined by arrangement considerations and requirements to reliable functioning of powerplant. Four turbofans NK-144 were disposed under wing close to each other. Each engine was provided with its own air intake ; two adjacent air intakes were tied together in common unit. Under-wing air intakes were flat and were provided with horizontal ramp.

Under supersonic conditions airflow can be decelerated in three oblique shock waves, in normal terminal shock wave and in subsonic diffuser. Each air intake operated by automatic control system which could change ramp position and by-pass flap depending on NK-144 engine setting. Engine nacelle length was defined by engine size and TsAGI and TsIAM requirements to air intake duct length needed for normal functioning of the engines. It should be noted that opposite to “Concorde” engines design where it was done as a single process, NK-144 engines engine nacelles with air intakes were designed in two mainly independent processes which led to re sizing of engine nacelles and further to many lack of co-ordination in operation of engines and air intake system. Braking system was supposed to be introduced at landing at the expense of reverser; reverser was planned to be installed on two outer engines (reverser system was not developed which resulted in operation of prototype and production machines with drag parachute). Main landing gear were retracted into wing, nose leg was retracted into forward fuselage space between two air intakes. Small wing height required reduction of wheels dimensions. It resulted in using twelve-wheeled bogie with rather small diameters of wheels. Main fuel resource was kept in wing integral fuel tank. Forward integral wing fuel tanks and additional tail integral fuel tank served for aircraft balancing. Main activities on selecting of optimal aerodynamic configuration of TU-144 a/c were headed by G.A.Cheryomukhin, powerplant optimization was performed by B.Voul department. In TU-144 a/c many principle approaches of remote control system. In particular signals of stability and controllability were tried out in longitudinal and azimuth channels. Under certain conditiona said activities made it possible to perform flight at static instability.Saelection of concept of TU-144 a/c contrls system mainly is a desert of G.F. Naboitshikov. L.Rodnianskiy made a substantial contribution to creation and development of this principally new control system. Pilot cockpit was designed according to requirements of up-to-date ergonomics. It was designed for four seats: two forward seats were intended for pilot and co-pilot, flight engineer was seated behind them, the forth seat was intended for engineer – experimentor in the first prototype. Further the flight crew was supposed to be limited by three pilots. Cabin interior arrangement and finishing of TU-144 a/c cabin were state-of-the art level, the most new finishing materials. Flight and navigation equipment was the best of our native avionics: perfect autopilot and airborne computer could maintain heading automatically. Pilots could see in instrument panel display where aircraft was at certain moment and how many kilometers are left to destination point. Approach was performed automatically at any time of a day under severe weather conditions etc. – all these represented a serious break-through for our aviation.

Building of the first prototype of TU-144 (“044”) was started in 1965. Simultaneously the second prototype was being built for static tests. Prototype “044” was initially intended for 98 passengers, later on this number was increased to 120. Correspondingly design take-off weight was increased from 130 tones to 150 tones. The prototype was built at “Opyt” Plant. In 1967 main aircraft components assembly was completed. In late 1967 the “044” prototype was moved to Zhukovskiy where the aircraft was being added with lack parts during all year 1968.

Simultaneously flights of analogs Mig-21I (A-144, “21-11”) were started. Th analog was built in DB named after A.I.Mikoyan. Its wing was similar to the one of “044” prototype from aerodynamic and geometric point of view. In total they built two “21-11” machines. Many test pilots operated these airplanes including those who tested TU-144 a/c in future including E.V.Yelian. The analog-airplane was successfully operated up to 2500 km/h. Records of these flights served as a basis for final correction of TU-144 wing and allowed test pilots to adopt to the aircraft features.

In late 1968 the “044” prototype (side No.68001) was prepared for the first flight. The flight crew was assigned as follows: test pilot E. Yelian , co-pilot – M.Kozlov, leading test engineer V.Benderov and flight engineer Y. Seliverstov. In view of novelty and uncommonness of the new machine the Design Bureau began extraordinary approach: it was first time when prototype passenger aircraft was provided with ejection crew seats. During whole month they performed engines running, rolling, final ground checks of the systems. From the end of December , 1968, the machine was completely ready to perform the first flight. And finally on the last day of 1968 “044” lifted-off in Zhukovskiy for the first time and rapidly climbed. The first flight lasted for 37 minutes. The flight was followed by analog-aircraft “21-11”.