Profile – Concorde SST

To many of those who take an active interest in aviation, there is one aircraft that symbolises the epitome of air travel. This aircraft is the Anglo-French Concorde.

It has not been without its problems, either. Apart from the obvious technical problems inherent in such a revolutionary and somewhat radical design, not to mention the bureaucratic pressure brought forth by critics early in its inception, the Concorde has borne the brunt and has been the subject of intense lobbying and criticism from environmentalists in later years.

From 1956 onwards, the world’s foremost aeronautically advanced nations, principally Britain, France, the United States and the USSR began independent serious design studies for supersonic commercial transport.

Several design proposals were adopted for full-scale testing evaluation. Among these ideas were a wide variety of designs, including exotic arrows and “M” shaped wings, but the one-wing design that was ultimately decided upon was that of the slender delta.

Thanks to the discovery of sophisticated design theory captured by the Allies with the demise of Hitler’s Third Reich, designers were able to reduce design time considerably.

Of these theories, the slender delta was one. Two German scientists, Dietrich Kuchemann and colleague E. C. Maskell, designers of the famous Messerschmitt Company, were the men whose work would be ultimately responsible for Concorde’s wing shape.

Their theory was simplicity within itself. It was based on the paper dart principle. As theory has it, sharp leading edges create their own airflow, a detached airflow that is caused by turbulence. This airflow separates from the wing surface and thus causes loss of lift. Usually, this causes stalls to occur prematurely and therefore disaster.

Kuchemann and Maskell reasoned that a slender delta wing creates its lift from an unknown airflow, from the detached airflow, the vortex rolls of air that the sharp leading edges generate over the wings on a sharp delta shape.

It was thought that, though theoretically practical, the slender delta was subjected to a “roadblock” effect over an incidence of 3°.

The Americans therefore went their own way, investing heavily in a complicated swing-wing proposal and, to cut a long story short, cancelled the project when the Senate denied further funds for it on the nights of May 19 and 20, 1971. Over $1 billion had been outlaid up until that time, but the cost to the US aeronautical industry and ancillaries was even higher. Boeing, the eventual design winner in the US competition for an indigenous SST, was forced to lay off 7000 workers from its Seattle facility alone as the Boeing 2707 began its death throes. General Electric, the powerplant contractor, also suffered. Six thousand of its employees were laid off.

It had been decided that the complications outweighed the advantages to the US taxpayer and national pride took an understandable second place to public expenditure in a project which had been labelled by the US press as the commercial “White Elephant” counterpart to the troubled F-111. It had been said that it would be a tragedy for the United States not to have an SST, but socially it was a tragedy not proceeding with it.

But, on a brighter note, independent studies in Britain and France had ended in similar conclusions from about 1959-61 and, from 1961-62, preliminary discussions between the two countries had begun.

On November 29, 1962, the British and French Governments signed an agreement covering the joint design development and manufacture of an SST. This so-called MACH 2 Entente was signed jointly by Julian Amery, Britain’s Minister for Aviation, and Geoffroy de Courcel, French Ambassador in London. The cost initially outlaid was put at £1000-£1500 million, a figure conveniently figured to be split evenly between the two participants, though in later years Britain would shoulder a more than 50/50 share in development expenditure.

Aircraft that had paved the way to this amalgamation of design studies by the two nations included, on the British side: the Type 188, a MACH 3 all stainless steel aircraft whose skin was designed to resist heat at speeds over 2000 mph. It taught the design teams that the heat barrier was far more crucial to supersonic flight than the sound barrier. Other experimental aircraft included the delta-winged HP-115, which aided research in low-speed flight characteristics, and another, the SAC 221 high-speed delta, correlating data in the high-speed flight envelope.

Service types such as the Vulcan bomber and the Lightning interceptor, already proven through active use, also played their part. The ill-fated TSR-2 bomber’s research was not wasted either but was put to more successful use and the SAC 223 delta provided much of the final development for the eventual Concorde design.

On the French side of the Channel, the French had already begun work on their supersonic. With considerable experience gained with their uniquely familiar Dassault Mirage, as well as research aircraft like the Sud Durandal and Nord Griffon which exceeded MACH 2 in 1959, the French were in a better position as a design partner in SST production techniques.

The outcome was the “Super Caravelle”, a medium-range four-engine transport that would replace and emulate the Caravelle, its successful subsonic namesake. This experience gained while working on the Super Caravelle gave the French an added advantage as a design partner.

After two years of detailed work and study, the prototype design studies were frozen in a re-examination of the two countries’ requirements and the aircraft’s technical requirements. At the conclusion of this, work on a prototype began.

When design work was again resumed a year later, the Concorde was a bigger plane. It was now 14 feet longer in the fuselage, the wings were 15 per cent larger, it would have bigger engines and, therefore, it would weigh 40,000 pounds more. Most importantly of all, it was to carry more passengers, a maximum of 118, over almost 4000 miles.

The year 1964 also saw the near cancellation of the Concorde by Britain when, in October, Harold Wilson’s Labour Party came to power. That year saw the cancellation of several promising indigenous aircraft projects. The TSR-2 supersonic bomber came under the axe, the same fate was dealt to the P1154 VTOL fighter as was to the HS-681 STOL freighter. And to this moratorium list, the Concorde seemed certain to be added. However, subjected to obligations from the 1962 agreement, pressure from France led by De Gaulle, the French aviation industry and SAC, on top of a threatened international lawsuit, the British Government had little alternative but to proceed with the project.

Metal was cut for the prototypes in April 1965, with four airframes taking shape, two prototypes and two structural test beds. The latter were assembled in special rigs – one at Toulouse, the other at Farnborough.

Within these rigs, the test airframes were subjected to extreme hot and cold temperatures while hydraulic jacks unmercifully tortured the structure to stresses equal to and above that which it was designed to accept deliberately breaking areas towards the conclusion of this program.

To add to this, an elaborate flight environment simulator was constructed at Farnborough, enabling simulation of actual flights in about one-third of the time. This specially constructed “jacket” was blown hot and cold air, the entire system being designed to examine the airframe’s fatigue strength when subjected to the elements. By the end of 1974, the system had completed 6800 test cycles, and produced 7000 test flights thereafter. This enabled it to keep one step ahead of the real Concorde.

No other aircraft has, in the history of aviation, been subjected to such thorough, if not necessarily vital, testing. Back-up rigs supported the larger rigs and minor sections were tested between the two test centres. The windscreens and windshield, so vital to a flight crew’s command of any situation, were subjected to – and if it were not so important it would be hilarious – punishment in the form of literally catapulting dead chickens at them to determine their impact strength in the event of a bird strike.

A monstrous rig for testing the fuel system was constructed also, the entire system would rear up via hydraulic jacks, to simulate accelerations, oscillate to stir the fuel around in the tanks and stand at high angles of incidence to force the pumps to work uphill.

At Blagnac Airport, Toulouse, the hydraulic rig assembled there included the full flight control and undercarriage systems. This rig was linked to the design simulator, also housed in the same building, enabling the rig to be controlled from an actual flight deck.

This particular simulator was entered into service in 1966 and played a substantial part in the design of the Concorde. From its inception, the simulator was used to study Concorde’s flight characteristics, characteristics of an aircraft that had not yet flown.

Though the system could, by no means, give an accurate representation of the Concorde’s behaviour in flight, it did surprisingly reproduce a very close simulation of the real thing, though it was a little harder to fly. Additionally, the system provided training to the crews who would eventually undertake the first flights.

The construction of the prototypes and subsequent production models of the Concorde were shared equally between Britain and France. Factories throughout Europe and the USA participated in the production of components, these being shipped to the factories at Toulouse and Filton to be assembled together to form complete sub-assemblies.

Production of certain sections of the Concorde was given to specialised centres. The wing and centre fuselage were made at Toulouse, the nose and tail at Filton, the engines in England, and the intakes in France. Once each sub-assembly was completed, it would be either incorporated into that particular factory’s own production line or it would be transported across the Channel, usually via the “Super Guppy” air freighter, to the other factory. This way, the two factories assembled alternate aircraft throughout production.

Remembering that one participant worked in imperial measurements and the other in metric, there was little margin for error on either side, but at no time was the fit between the various sub-assemblies questionable.

After further detailed, extensive and exhaustive testing, the first prototype, the French-built Concorde 001 (F-WTSS), was rolled out of its assembly hangar in December 1967. Taxiing trials had been undertaken by August 1968 and a month later its companion, 002 (G-BSST), was completed at Filton. Testing of the chosen powerplant, the Rolls Royce Olympus 593 engine, had reached the 5000-hour mark by December 1968.

The first flight of the Concorde, by 001, had originally been conceived in February 1968, but several last-minute problems had forced this date to slip back. For instance, the taxiing trials of August 1968 revealed that there were problems with the brakes, which required extensive modifications.

Finally, on March 2, 1969, following two days of mist which accounted for a final delay, Concorde 001 took off from Toulouse.

This momentous occasion was followed on April 9, 1969, by the maiden flight of the British prototype, 002, from Filton. By this time, 001 had made a further eight flights.

British Aircraft Corporation’s chief test pilot on the Concorde project, Brian Trubshaw, was at the controls of 002 on its first flight – which did not pass without event.

First of all, the pilot’s airspeed indicator had continuously been registering erratically during runway trials. At a speed of 90 knots, the warning flag had appeared on the instruments, denoting inaccurate information, though the co-pilot’s airspeed indicator appeared to agree with that of the central speed indicator.

The engineers set to work to rectify the problem but were unsure of their success. As it turned out, the warning flag did not appear and a smooth take-off was performed. Shortly afterwards, however, a further complication appeared when the two radio altimeters failed, making a landing difficult.

Up until this time, landings for the test program had been effected in a much-simplified way, little knowledge being available as to the precise technique needed to combat the ground effect forces on the flight controls, thereby giving the Concorde the tendency to drop its nose. Therefore, power was maintained until touchdown so that, in the likelihood of an emergency, there would still be enough power to pull out.

In addition, the pilot’s position, some 35 feet above the nosewheels, made height judgment very difficult, the radio altimeters providing invaluable data as to the exact distance between the ground and the nosewheels.

While observers onboard attempted to rectify this failure, the flight crew had to contend with yet another problem. A light aircraft had strayed into the Concorde’s flight path. Unable to contact the pilot of this aircraft, the frustrated controller had to send “steers” to the Concorde to keep it away from danger. The light plane eventually moved out of the area but the Concorde’s other problem, its instruments, remained.

Therefore, Concorde 002’s first landing was not made with the aid of the sophisticated instruments at its disposal (and which were indisposed!) but by the simple, old-fashioned system of the pilot’s eyesight.

The entire flight, from Filion to Fairford, whose longer runway subsequently was used for later tests, took only 42 minutes, ironically the same time as that of 001’s maiden flight.

By July 10, 1969, the Concorde’s flight altitude had been raised to 40,000 feet from the previous 10,000 feet level, with an indicated flight speed of 380 knots and a MACH number of 0. 8 as compared to 250 knots at the lower altitude.

Concorde had, by this time, taken off at a weight of 133 tons, and had flown at a minimum speed of 138 knots and at an attack angle of 16. 5°. It had also accumulated a total flight time of 62 hours 18 minutes. From here on, tests as to the aircraft’s handling of flutter began.

Undertaken to determine the structural damping capabilities of Concorde, these tests carried out in flight were most important to the aircraft’s success in flight certification trials. In these experiments, the control surfaces are forced to operate with a violent suddenness and are then relaxed. The reason behind this is to determine the length of time it takes for the resulting oscillations to fade away and to see to what degree the aircraft’s structure absorbs them.

At the conclusion of these tests, the prototypes were grounded while the factories attached the variable intakes to them to ensure their attaining MACH 1 and over.

Following these modifications, assessments by the first airline pilots began (BOAC, Air France, Pan Am and TWA taking part in this program), each flying Concorde 001 for about two hours.

The following year, 1970, continued to see Concorde entering the flight environment that it would have to fly in once the production aircraft were in service. That year, both 001 and 002 attained MACH 2 at a height of 52,000 feet.

As MACH 1. 5 had been gradually achieved, the “high risk” phase began and, unable to afford the loss of either prototype, was carried out methodically and carefully using the simulator before any manoeuvres were attempted.

These tests at high MACH were flown down the west coast of England, a straight line extending from the northern tip of Scotland, over the Irish Sea, skirting the easternmost point of Ireland and over the southern tip of England. This “Boom Alley” was so planned as to give good radar coverage and safe proximity to emergency airfields and rescue services.

During this period, complaints from the public began to become more and more frequent, and the resulting press coverage provided the anti-SST lobbyists with further fuel to add to their fire. These flight tests included those for flutter, slam acceleration, sideslip, pushover (which caused negative “g” forces) and single and double engine shut-downs.

Throughout the entire flight development program of the Concorde, there was only one significant structural failure. This occurred in January 1971 when prototype 001, while cruising at MACH 2 over the Atlantic Ocean southwest of Ireland, experienced a full power surge on both starboard engines. The drive mechanism of the forward intake ramp failed and the entire ramp, about three and a half feet by five feet in size, was sucked through the front intake at a flight speed of 540 knots – or MACH 1. 98 – at 49,000 feet.

Miscellaneous hardware passed through the No 4 engine, which continued to windmill after the crew shut it down, but little other damage was incurred and the prototype behaved without adverse characteristics throughout.

The Aerospatiale crew then proceeded to fly the aircraft 650 nautical miles to its Toulouse base on the remaining three engines, landing there safely.

One optimistic factor that was derived from this unpleasant incident was that Concorde could tolerate such damage, just as the design plans had stipulated. Subsequent experience has confirmed this data and the systematic fail-safe design and analysis of the aircraft, as well as its systems, emphasises the confidence entrusted by flight crews in the Concorde.

The year 1971 saw Concorde start to show the world what she was made of. President Pompidou of France flew in the prototype 001 as one of the first VIPs to do so, repeating this event again later when he flew to the Azores, Spain, to confer with President Nixon. On May 13, Concord made its first fully automatic landing.

Then, on May 28, the first supersonic intercontinental flight was undertaken, Concorde 001 flying 2800 statute miles to Dakar, Senegal, in two hours 35 minutes, halving subsonic times.

On its South American sales tour from September 4-8, 1971, Concorde demonstrated its compatibility with the then-existing airports and ATC procedures. December 17, 1971, saw the first pre-production version, 01 (G-AXDN), fly from Filton for the first time.

By June 1972, over 1000 hours had been tallied by the two prototypes and pre-production Concorde 01. At this stage, the Concorde began its sales tour of the Middle East, Far East and Australia, aircraft 002 visiting 12 countries in the Middle East and the Far East, completing a massive 45,000-mile round trip during this demonstration period.

BAC test pilot Brian Trubshaw piloted 002 on the tour but a slight mar to the aircraft’s otherwise punctual demonstration in each country was the massive contrails of smoke deposited into the air on take-off and landing. This occurred as a result of the aircraft’s early model engines which had not been installed with the improved combustion chambers, so designed as to eliminate the above problem.

On July 28, 1972, the British and French flag carriers, BOAC and Air France, signed agreements for five and four Concordes respectively, these being delivered from 1975 onwards. CAAC, China’s national airline, on July 24, signed a preliminary purchase agreement for two Concordes, making them the first customer for the airliner outside of the two participant countries; and added a third on August 28.

Other demonstration flights overseas continued, for instance, when Concorde 02 travelled to Dallas, Texas, for the opening of the new Dallas-Fort Worth Airport on September 20, 1973. Other visits include those to Rio de Janeiro, Brazil, and, in 1974, to the US West Coast, Peru, Colombia and Venezuela.

The Concorde ably demonstrated its speed when 02 flew from Boston to Paris and back, completing the round trip as an Air France 747, on the same leg, was en route. Coupled with this was the feat performed by 001 on June 30, 1973, when it paced the total eclipse of the sun across Africa, giving scientists their first sustained view of the sun’s corona.

The first production Concorde to fly in customer airline livery, 201, completed its maiden flight from Toulouse, in Air France colours, on December 6, 1973, reaching MACH 1. 57 on this occasion. This was followed by the second production aircraft, 202, in British Airways livery, on February 13, 1974, from Filton. Concorde had by now evolved through three distinct versions: prototype, pre-production and production. There had been two of the earlier models produced and a total of 16 production aircraft had been authorised.

Differences between the prototypes and the pre-production aircraft included an extended forward fuselage to accommodate additional seats on the latter, a new fully glazed visor for improved visibility for the flight crew and refined wings. The leading edges had been redesigned with twist and camber added to the outer panels.

More power was embodied in the engines, while two additional features were included for the production aircraft. These were an extended tail cone, also fitted to 02, which would reduce drag at MACH 2, and new thrust reverser/nozzle units for the rear end of the engines. Concorde was now capable of carrying up to 128 passengers and their luggage on trans-Atlantic routes.

In February 1974, Concorde 02 conducted cold climate trials at Fairbanks, Alaska, while aircraft 002 flew to Jan Smuts Airport, Johannesburg, for performance trials in a “hot and high” climate.

From May 27 to June 5, 1974, Concorde 02 flew a 10-day trial service between Paris and Rio de Janeiro, setting a record 11 hours 28 minutes and covering 11,540 statute miles in that time, from Paris to Rio and back.

The first supersonic flight over a US domestic route, between Boston and Miami, occurred on June 14 1974 followed three days later by the first double crossing of the Atlantic.

From August 7 to September 2, 1974, the second production Concorde visited the Persian Gulf and Singapore, conducting hot weather trials. Then, from October 4 to November 11, Concordes 201 and 202 completed another milestone when Airworthiness Certification trials were successfully carried out at Casablanca, Turkey October 20-28, and the supersonic age came to the American Pacific Coast with the visit of Concorde 02. November 16 to December 4, 1974, saw Concorde 01 at Moses Lake, Washington, testing its de-icing systems.

The seventh Concorde to fly and the third production aircraft to wear airline livery, that of Air France, made its maiden flight on January 31, 1975. This was followed on February 27 by the fourth production aircraft in British Airways colours.

Special Category Certificate of Airworthiness was granted by the French authorities to Concorde 203 on May 28, 1975, followed on July 7 by similar British approval to aircraft 204.

Concorde is powered by four Rolls Royce/SNECMA Olympus 593 Mark 610 engines which, together, produce 152,000 lb of thrust at take-off and 27,160 lb of thrust during cruise at 60,000 feet.

These engines are indeed noisy, as environmentalists would be quick to point out, but it was of necessity rather than choice that they were constructed so. They have to be narrow in cross-section, so as to minimise drag, and have a high exhaust velocity which is also needed, otherwise the exhaust itself would cause enough drag to slow the aircraft. These requirements necessitate an engine with a low by-pass ratio.

Most commercial subsonic airliners are powered by engines of a high by-pass ratio. This type of engine has a number of advantages, such as comparative quietness as a result of their large fans, which act like propellers moving a large mass of air slowly, whereas a turbojet moves a smaller mass of air faster.

The major factor that produces the excessive noise is the mixing of the exhaust with the static air outside, producing a sort of “tearing” or “ripping” effect. Thus a turbojet is and was disadvantageous, but the Olympus was, at the time, the only powerplant capable of producing the amount of power necessary for Concorde.

As there is no engine yet developed that can accept air through its compressors at supersonic speeds, the air must be slowed down from MACH 2 to MACH 0. 5 to allow it to pass through the engine. This is facilitated by the use of the 11-foot length of the air intake. By this method, the ramps and spill doors incorporated into the structure, which are hydraulically controlled by a computer, either let in more air when it is required (ie, at take-off) or bleed it off. At about MACH 1. 3, the ramps come into motion, lowering themselves and causing a series of shock waves beginning at the bottom lip of the intake. These tend to slow the air down.

At MACH 2, the air is not only slowed down but also compressed and raised in temperature. This helps the engines’ compressors to work less, although the 200°c temperature necessitates special construction materials in the engine.

PERFORMANCE: Concorde can attain a maximum cruise speed of 1354 mph (2179 kmh) at 51,300 ft (15,635 m) or MACH 2. 05; a range with maximum fuel (22,250 lb/10,092 kg payload and FAR reserves) of 3915 miles (6300 km), with max payload (28,000 lb/12,700 kg) at MACH 0. 93 at 30,000 ft (9145 m), 3063 miles (4930 km), at MACH 2. 05, 3869 miles (6226 km); initial climb rate of 5000 ft/min (25 m/sec); service ceiling (approx) 60,000 ft (18,300 m).

WEIGHTS: Operational empty weight amounts to 174,750 lb (79,265 kg); max take-off, 400,000 lb (181,435 kg).

ACCOMMODATION: A normal flight crew of three and one-class seating for 128 or an alternative high-density arrangement for 144 passengers.

Possibly one of the most remarkable features of the Concorde is its “droopable” nose cone and visor. This idea came about because of the high angle of attack of some 13° which the Concorde must fly on its final approach to the runway. Because of the aircraft’s large, slender nose, the pilot would normally only have about 5° of downward vision.

Retention of the streamlined nose is necessary during supersonic flight, but the nose can be drooped into four positions, three of which are used on every flight. At all speeds above an indicated airspeed of 250 knots (or about 290 mph), the nose and visor must be fully up.

The visor, which covers the windscreen, can be lowered independently into a recess in the nose, but the position is seldom used except during a transit stop when the windscreen requires cleaning.

Navigational aids built into Concorde’s flight deck include the omnipresent, by today’s standards, inertial navigation system (INS), of which Concorde has three. The INS is a combination of highly accurate gyros and accelerometers, connected electronically to one another via a small computer.

Upon start-up, the system, which is completely independent of any outside interference other than the force of gravity and the velocity of the aircraft, needs only to be told its position in order that it can align itself with true north and the horizon. With changes in velocity, the computer adjusts the aircraft’s relative position in accordance with that which it has been programmed.

To avoid an error on long-distance international flights, even of only two miles, the Concorde’s three onboard navigational computers confer with each other, compare their data and a “best-estimated position” is worked out on a continuous basis from there.

Navigational aids on the ground help the INS to accurately define the real position of the Concorde. Radar pulses are emitted to the DME (Distance Measuring Equipment) and, depending on the frequency used, the time interval between transmission and reception defines the real distance between the aircraft and the ground stations.

In order to travel along a precisely defined route, the CDU (Control and Display Unit) is utilised. Waypoints are used to achieve an accurate path, nine of which are available. These are programmed into the computer with a simple program card and optical card reader, the whole system being reprogrammable as each waypoint is passed, but three or four are usually all that is required.

The latest news on the Concorde, which has to date cost British taxpayers almost $1700 million, is that it will be allowed to continue flying despite attempts to scrap it. Obviously, as substantiated by the British Department of Trade, the cost of scrapping Concorde would negate the expenditure presently outlaid to keep it flying.

The official decision followed a recommendation made by an all-party parliamentary committee in April 1980 which suggested that, unless means were found of cutting operating costs, Concorde should be scrapped. But, as costs for production were now falling, it would cost twice as much to end it as it cost to start it.

The slow and painful progress of man towards one world has always, throughout history, been limited by his means of transportation – the horse, the coach, the sailing ship, the railways, the steamship, the automobile, the aeroplane and the jet plane. Concorde is only the latest in a series of steps of technological progress. In time it, too, will be surpassed by 21st-century science. But, whatever comes hence, Concorde’s place in history will be assured for all time.