That honor goes to the British-built English Electric (now BAE Systems) Lightning – in 1954. The British Aircraft Corporation (BAC) Tactical Strike/Reconnaissance 2 (TSR-2 – first flight September 1964) and the Soviet Tupolev Tu-144 Charger transport aircraft (1969) were among the first specifically designed to cruise supersonically.
English Electric Lightning
The English Electric Lightning is a supersonic jet fighter aircraft of the Cold War era, noted for its great speed and unpainted metal exterior finish. It is the only all-British Mach 2 fighter aircraft and was the first aircraft in the world capable of supercruise. The Lightning was renowned for its capabilities as an interceptor; pilots commonly described it as "being saddled to a skyrocket". Following English Electric's integration into the unified British Aircraft Corporation, the aircraft was marketed as the BAC Lightning.
The Lightning was prominently used by the Royal Air Force RAF and the Royal Saudi Air Force. The aircraft was a regular performer at airshows, it is one of the highest-performance aircraft ever used in formation aerobatics. Following retirement in the late 1980s, many of the remaining aircraft became museum exhibits; until 2010, three examples were kept flying at "Thunder City" in Cape Town, South Africa. In September 2008, the Institution of Mechanical Engineers conferred on the Lightning its "Engineering Heritage Award" at a ceremony at BAE Systems' site at Warton Aerodrome.
Origins
The specification for the aircraft followed the cancellation of the Air Ministry's 1942 E.24/43 supersonic research aircraft specification which had resulted in the Miles M.52 programme. It was soon realised that the aircraft should be regarded as a prototype fighter to satisfy the British Air Ministry's 1949 specification F23/49 rather than being a pure research aircraft. The Lightning design shared a number of innovations first planned for the Miles M.52 including the shock cone and all-moving tailplane or stabilator. The prototypes, known as P.1, were built to Ministry of Supply Operational Requirement ER.103 of 1947 for a transonic research aircraft. The first of the two P.1s WG760 flew for the first time from RAF Boscombe Down on 4 August 1954.
The P.1's chief designer was W.E.W "Teddy" Petter, formerly chief designer at Westland Aircraft. The design was controversial, and the Short SB5 was built to test wing sweep and tailplane combinations. The original combination was proved correct. The forerunner of the Lightning series was the P.1A and P.1B flying "proof-of-concept" aircraft. Looking very much like the production series, the prototypes were distinguished by the rounded-triangular intakes, short fins and lack of radar or operational equipment. Initial prototypes were powered by un-reheated Armstrong Siddeley Sapphire turbojets, although the Rolls-Royce Avon was used in subsequent aircraft. On 25 November 1958, the P.1B became the first British aircraft to fly at Mach 2. The second P.1A, WG763 was fitted with two 30mm ADEN cannons, however it was not possible to equip heavy underwing stores. Due to the limited internal space of the fuselage the fuel capacity was relatively small, giving the prototypes an extremely limited endurance, additionally the tyres would rapidly wear out.
Production
The first operational Lightning, designated the F.1, was designed as a point defence interceptor to defend mainland Britain from bomber attack. To best perform this intercept mission, emphasis was placed on rate-of-climb, acceleration, and speed, rather than range and combat endurance. It was equipped with two 30 mm ADEN cannon in front of the cockpit windscreen and an interchangeable fuselage weapon pack containing either an additional two ADEN cannon, 48, two inch air-to-air rockets, or two de Havilland Firestreak air-to-air missiles, a heavy fit optimized for attack of large aircraft. The Ferranti A.I.23 radar supported autonomous search, automatic target tracking, and ranging for all weapons, while the pilot attack sight provided gyroscopically derived lead angle and backup stadiametric ranging for gun firing. The radar and gunsight were collectively designated the AIRPASS: Airborne Interception Radar and Pilot Attack Sight System.
The next two Lightning variants, the F.1A and F.2, saw steady but relatively minor refinement of the basic design, and the next variant, the F.3, was a major departure. The F.3 had higher thrust Avon 301R engines, a larger, squared-off fin and strengthened intake bullet allowing a service clearance to Mach 2.0 (the F.1, F.1A and F.2 were limited to Mach 1.7), the A.I.23B radar and Red Top missile offering a limited forward hemisphere attack capability—and most notoriously—deletion of the nose cannon. The new engines and fin made the F.3 the highest performance Lightning yet, but with an even higher fuel consumption and resulting shorter range. The next variant, the F.6, was already in development, but there was a need for an interim solution to partially address the F.3’s shortcomings. The F.3A was that interim solution.
The F.3A introduced two improvements: a new, non-jettisonable, 610 gal (2,770 l) ventral fuel tank, and a new, kinked, conically cambered wing leading edge, incorporating a slightly larger leading edge fuel tank, raising the total usable internal fuel to 716 gal (3,250 l). The conically cambered wing noticeably improved maneuverability, especially at higher altitudes, and the ventral tank nearly doubled available fuel. The increased fuel was very welcome, but the lack of cannon armament was felt to be a deficiency. It was thought that cannon were desirable to fire warning shots in the intercept mission.
The F.6 was the ultimate Lightning version to see British service. Originally, it was nearly identical to the F.3A with the exception that it had provisions to carry 260 gal (1,180 l) ferry tanks on pylons over the wings. These tanks were jettisonable in an emergency, and gave the F.6 a substantially improved deployment capability. There remained one glaring shortcoming: the lack of cannon. This was finally rectified in the form of a modified ventral tank with two ADEN cannon mounted in the front. The addition of the cannon and their ammunition decreased the tank's fuel capacity from 610 gal to 535 gal (2,430 l), but the cannon made the F.6 a “real fighter” again.The final British Lightning was the F.2A. This was an F.2 upgraded with the cambered wing, the squared fin, and the 610 gal ventral. The F.2A retained the A.I.23 and Firestreak missile, the nose cannon, and the earlier Avon 211R engines. Although the F.2A lacked the thrust of the later Lightnings, it had the longest tactical range of all Lightning variants, and was used for low-altitude interception over Germany.
Overview
There were several unique and distinctive features in the design of the Lightning; principally the use of stacked and staggered engines, a notched delta wing, and a low-mounted tailplane. The vertically stacked, longitudinally staggered engines was the solution devised by Petter to the conflicting requirements of minimizing frontal area, providing undisturbed engine airflow across a wide speed range, and packaging two engines to provide sufficient thrust to meet performance goals. The configuration allowed the twin engines to be fed by a single nose inlet, with the flow split vertically aft of the cockpit, and the nozzles tightly stacked, effectively tucking one engine behind the cockpit. The result was a low frontal area, an efficient inlet, and excellent single-engine handling. Unfortunately, this stacked configuration led to complicated maintenance procedure, and the recurring problem of fluid leakage from the upper engine being a fire hazard.
The fuselage was tightly packed, leaving no room for fuel tankage or main landing gear. While the notched delta wing lacked the volume of a standard delta wing, each wing contained a fairly conventional three-section main fuel tank and leading-edge tank, holding 312 imp gal (1,420 l); the wing flap also contained a 33 imp gal (150 l) fuel tank and an additional 5 imp gal (23 l) was contained in a fuel recuperator, bringing the aircraft's total internal fuel capacity to 700 imp gal (3,200 l). The main landing gear was sandwiched outboard of the main tanks and aft of the leading edge tanks, with the flap fuel tanks behind. The long main gear legs retracted toward the wingtip, necessitating an exceptionally thin main tyre inflated to the high pressure of 330–350 psi (23–24 bar).
A conformal ventral store was added to the design to house, alternatively, a fuel tank or a rocket engine. The rocket engine, a Napier Double Scorpion motor, also contained a reserve of 200 imp gal (910 l) of high-test peroxide (HTP) to drive the rocket’s turbopump and act as an oxidizer. Fuel for the rocket would have been drawn from the Lightning’s internal tankage. The rocket engine was intended to boost the Lightning’s performance against a supersonic, high altitude bomber threat, but this threat never emerged, thus Lightning’s basic performance was deemed sufficient and the rocket engine option was cancelled in 1958. The ventral store saw wide use as an extra fuel tank, initially this was jettisonable and held 250 gal (247 gal usable, 1,120 l). Later ventral tanks were non-jettisonable.
Despite its acceleration, altitude and top speed, the Lightning found itself outclassed by newer fighters in terms of radar, avionics, weapons load, range, and air-to-air capability. More of a problem was the obsolete avionics and weapons fit. The radar had a short range and no track-while scan capability; it could only detect targets in a fairly narrow (40 degree arc). While an automatic collision course attack system was developed and successfully demonstrated by English Electric, it was not adopted owing to cost concerns. Plans to supplement or replace the obsolete Red Top and Firestreak missiles with modern AIM-9L Sidewinder missiles never came to fruition because of lack of funding,
Speed
Early models of the Lightning the F.1, F.1A, and F.2, had a rated top speed of Mach 1.7 at 36,000 ft in an ICAO standard atmosphere, and 650 KIAS (Knots Indicated Airspeed) at lower altitudes. Later models, the F.2A, F.3, F.3A, F.6, and F.53, had a rated top speed of Mach 2.0 at 36,000 ft, and speeds up to 700 KIAS for “operational necessity only. A Lightning fitted with Avon 200-series engines, a ventral tank and two Firestreak missiles typically ran out of excess thrust at Mach 1.9 on a Standard Day; while a Lightning powered by the Avon 300-series engines, a ventral tank and two Red Top missiles ran out of excess thrust at Mach 2.0. As speed increased, the Lightning's directional stability decreased; there were potentially hazardous consequences in the form of vertical fin failure if yaw yaw was not rapidly counteracted by correct ruder use. Stability was protected by imposed Mach limits during missile launches; later Lightning variants featured a larger vertical fin which gave a greater stability margin during high speed flight.
Supersonic speeds also threatened inlet stability; the inlet's central shock cone served as a compression surface, diverting air into the annular inlet. As the Lightning accelerated through Mach 1, the shock cone generated an oblique shock positioned forward of the intake lip; known as a subcritical inlet condition, this is stable but also produces inefficient spillage drag. Around the Design Mach speed, the oblique shock is positioned just in front of the inlet lip and efficiently compressed the air without any spillage. As speed increases beyond Design Mach, the oblique shock becomes supercritical, where supersonic airflow enters the inlet duct. The Lightning’s inlet was designed to handle only subsonic air, a supercritical state not only drastically reduced engine thrust output but could lead to surges or a compressor stall, which could result in engine flameout and/or damage.
Thermal and structural limits were also present; as air is heated up when compressed by the passage of an aircraft. This heating increases considerably when at supersonic speeds. The airframe absorbs heat from the surrounding air, the inlet shock cone at the front of the aircraft becoming the hottest part. The shock cone was composed of fibreglass, necessary because the shock cone also served as a radar radome; a metal shock cone would interfere with the AI 23’s radar emissions. The shock cone would be eventually weakened due to the fatigue caused by the thermal cycles involved in regularly performing high-speed flights. At 36,000 ft and Mach 1.7, the heating conditions on the shock cone would be similar to those at Sea Level and 650 KIAS, but if the speed was increased to Mach 2.0 at 36,000 ft, the shock cone would be exposed to temperatures more than 70% higher than those at Mach 1.7. The shock cone was strengthened on the later Lightning F.2A, F.3, F.6, and F.53 models, thus allowing routine operations at up to Mach 2.0.
The small-fin variants could exceed Mach 1.7, but the stability limits and shock cone thermal/strength limits made such speeds risky. The large-fin variants, especially those equipped with Avon 300-series engines could safely reach Mach 2, and given the right atmospheric conditions, might even achieve a few more tenths of a Mach. All Lightning variants had the excess thrust to slightly exceed 700 KIAS under certain conditions, and the service limit of 650 KIAS was occasionally ignored. With the strengthened shock cone, the Lightning could safely approach its thrust limit, but fuel consumption at very high airspeeds was excessive and became a major limiting factor.
Climb
The Lightning possessed a remarkable climb rate. It was famous for its ability to rapidly rotate from takeoff to climb almost vertically from the runway, though this did not yield the best time to altitude. The Lightning's trademark tail-stand manoeuvre exchanged airspeed for altitude; it could slow to near-stall speeds before commencing level flight. The Lightning’s optimum climb profile required the use of afterburners during takeoff. Immediately after takeoff, the nose would be lower for rapid acceleration to 430 KIAS before initiating a climb, stabilising at 450 KIAS. This would yield a constant climb rate of approximately 20,000 ft/min. Around 13,000 ft the Lightning would reach Mach 0.87 and maintain this speed until reaching the tropopause, 36,000 ft. on a standard day. If climbing further, pilots would accelerate to supersonic speed at the tropopause before resuming the climb.
A Lightning flying at optimum climb profile would reach 36,000 ft in under three minutes. The official ceiling was kept as a secret, although low security RAF documents usually stated 60,000+ ft (18 000+ m). In September 1962 Fighter Command organised several supersonic interception trials on Lockheed U-2As at heights of around 60,000-65,000 ft, which were temporarily based at RAF Upper Heyford to monitor Soviet nuclear tests. RAF Lightning pilot and Chief Examiner Brian Carroll reported taking a Lightning F.53 up to 87,300 feet (26 600 m) over Saudi Arabia at which level "Earth curvature was visible and the sky was quite dark", noting that control-wise "[it was] on a knife edge".
In 1984, during a major NATO exercise, Flt Lt Mike Hale intercepted a U-2 at a height which they had previously considered safe from interception. Records show that Hale climbed to 88,000 ft (26,800 m) in his Lightning F.3 XR749. This was not sustained level flight, but in a ballistic climb or a zoom climb, in which the pilot takes the aircraft to top speed and then puts the aircraft into a climb, trading speed for altitude. Hale also participated in time-to-height and acceleration trials against Lockheed F-104 Starfighters from Aalborg. He reports that the Lightnings won all races easily with the exception of the low-level supersonic acceleration, which was a "dead heat".
Carroll compared the Lightning and the F-15C Eagle, having flown both aircraft, stating that: "Acceleration in both was impressive, you have all seen the Lightning leap away once brakes are released, the Eagle was almost as good, and climb speed was rapidly achieved. Takeoff roll is between 2,000 and 3,000 ft [600 to 900 m], depending upon military or maximum afterburner-powered takeoff. The Lightning was quicker off the ground, reaching 50 ft [15 m] height in a horizontal distance of 1,630 feet [500m]". Chief Test Pilot for the Lightning Roland Beamont, who also flew most of the "Century series" US aircraft, stated his opinion that nothing at that time had the inherent stability, control and docile handling characteristics of the Lightning throughout the full flight envelope. The turn performance and buffet boundaries of the Lightning were well in advance of anything known to him.
Tupolev Tu-144
The Tupolev Tu-144 (NATO name: "Charger'") was a supersonic transport aircraft (SST) and remains one of only two SSTs to enter commercial service, the other being Concorde. The design, publicly unveiled in January 1962, was constructed under the direction of the Soviet Tupolev design bureau, headed by Alexei Tupolev.
The prototype first flew on 31 December 1968 near Moscow, two months before the first flight of the Concorde. The Tu-144 first went supersonic on 5 June 1969, and on 15 July 1969 became the first commercial transport to exceedMach 2.
A Tu-144 crashed in 1973 at the Paris Air Show, delaying its further development. The aircraft was introduced into passenger service on 1 November 1977, almost two years after the Concorde. In May 1978, another Tu-144 (an improved version, named Tu-144D) crashed in a test flight while being delivered, and the passenger fleet was permanently grounded after only 55 scheduled flights. The aircraft remained in use as a cargo plane until 1983, by which point a total of 102 commercial flights had been completed. The Tu-144 was later used by the Soviet space programme to train pilots of the Buran spacecraft, and by NASA for supersonic research.
Development
The Soviet government published the concept of the Tu-144 in an article in the January 1962 issue of the magazine Technology of Air Transport. The air ministry started development of the Tu-144 on 26 July 1963, 10 days after the design was approved by the Council of Ministers. The plan called for five flying prototypes to be built in four years, with the first aircraft to be ready in 1966.
Despite the close similarity in appearance of the Tu-144 to the Anglo-French supersonic aircraft, there were significant differences in the control, navigation and engine systems. In areas such as range, braking and engine control, the Tu-144 lagged behind the Concorde, but aerodynamics of the Soviet aircraft was better. While the Concorde utilized an electronic engine control package from Lucas, Tupolev was not permitted to purchase it for the Tu-144 as it could also be used on military aircraft. The Concorde's designers used the fuel of the airliner as the coolant for air conditioning the cabin and the hydraulic system (see Concorde for details). Tupolev installed additional equipment on the Tu-144 to accomplish this, increasing the weight of the airliner.
Alexei A. Tupolev continued to work to improve the Tu-144 with upgrades and changes were made on the Tu-144 prototype. While both the Concorde and the Tu-144 prototype had ogival delta wings, the Tu-144's wing lacked Concorde's conical camber. Production Tu-144s replaced this wing with a double-delta wing including conical camber, and they added a simple but practical device: two small retractable canard surfaces, one on either side of the forward section on the aircraft, to increase lift at low speeds.
Moving the elevons downward in a delta-wing aircraft increases the lift, but also pitches its nose downward. The canard cancels out this nose-downwards moment, thus reducing the landing speed of the production Tu-144s to 315–333 km/h (196–207 mph; 170–180 kn), still faster than that of the Concorde. The NASA study lists final approach speeds during Tu-144LL test flights as 315–335 km/h (196–208 mph; 170–181 kn), however these were approach speeds exercised during test flights specifically intended to study landing effects at maximum possible range of speeds, regardless of how hard and stable the landing can be. As to regular landings, FAA circular lists Tu-144S approach speed as 329 km/h (204 mph; 178 kn), as opposed to the Concorde's approach speed of 300 km/h (190 mph; 160 kn) 162 kn (300 km/h), based on the characteristics declared by the manufacturers to Western regulatory bodies. It is open to argument how stable the Tu-144S was at the listed airspeed. In any event, when NASA subcontracted Tupolev bureau in the 1990s to convert one of the remaining Tu-144D to a Tu-144LL standard, the procedure set by Tupolev for landing defined the Tu-144LL "final approach speed... on the order of 360 km/hr depending on fuel weight." Brian Calvert, the Concorde's technical flight manager and its first commercial pilot in command for several inaugural flights, cites final approach speed of a typical Concorde landing to be 287–296 km/h (178–184 mph; 155–160 kn). The lower landing speed compared to Tu-144 is due to the Concorde's more refined design of the wing profile that provides higher lift at low speeds without degrading supersonic cruise performance – a feature often mentioned in Western publications on the Concorde and acknowledged by Tupolev designers as well.
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