One of the best-loved engineering design projects of the 20th century, CONCORDE (1976-2003) is an exceptional example of successful worldwide partnership. Its Anglo-French designers manufactured the world's first supersonic money-making passenger airplane. When this particular aircraft reaches its top speed it takes less than 3 hours to get to London from New York.
History of the Concorde
Concept
In the late 1950s, the United Kingdom, France, United States and Soviet Union were considering to develop a supersonic transport. The British Bristol Aero plane Company and the French Sud Aviation were both working on designs, called the Type 223 and Super-Caravelle, correspondingly. Both were largely fund by their individual governments. The British design was for a thin-winged delta shape for a transatlantic-ranged aircraft for about 100 people, while the French were intending to build an average-range aircraft.
The designs were both ready to start prototype construction in the early 1960s, but the cost was so great that the British government made it essential that BAC looks for global co-operation. Approaches were made to a number of countries, but only France showed real interest. The development project was negotiated as an international agreement between the two countries rather than a marketable agreement between companies and included a section, originally asked for by the UK, imposing heavy penalties for cancellation. A draft agreement was signed on 28 November 1962. By this time, both companies had been combined into new ones; thus, the Concorde project was between the British Aircraft Corporation and Aérospatiale. At first the new association intended to produce one long range and one short range version. However, prospective customers showed no interest in the short-range version and it was dropped. The association secured orders (i.e., non-binding options) for over 100 of the long-range version from the major airlines of the day: Pan Am, BOAC and Air France were the launch customers, with six Concordes each.
Naming
Reflecting the agreement between the British and French governments which led to Concorde's construction, the name "Concorde" is from the French word concorde, which has an English equivalent, concord, meaning in both languages, agreement, harmony or union.
The aircraft was primarily referred to in the UK as "Concorde", with the French spelling, but was officially changed to "Concord" by Harold Macmillan in response to a superficial slight by Charles de Gaulle. In 1967, at the French roll-out in Toulouse the British Government Minister for Technology, Tony Benn declared that he would change the spelling back to "Concorde". This created a nationalist chaos that died down when Benn stated that the suffixed "e" represented "Excellence, England, Europe and Entente (Cordiale)." In his autobiography, he recounts a tale of a letter from an irate Scotsman claiming: "[Y]ou talk about 'E' for England, but part of it is made in Scotland." Given Scotland's contribution of providing the tip cone for the aircraft, Benn replied, "[I]t was also 'E' for 'Écosse' (the French name for Scotland) - and I might have added 'e' for excessiveness and 'e' for escalation as well!"
Concorde also acquired an unusual nomenclature for an aircraft. In common usage in the United Kingdom, the type is known as "Concorde" rather than "the Concorde" or "a Concorde".
Design
General Features
Concorde is an ogival (the roundly narrowed end of a two-dimensional or three-dimensional object) delta-winged (a wing platform in the form of a triangle) aircraft with four Olympus engines based on those originally developed for the Avro Vulcan strategic bomber. Concorde was the first aircraft to have an (in this case, analogue) fly-by-wire (A fly-by-wire (FBW) system replaces manual flight control of an aircraft with an electronic interface) flight-control system; the avionics of Concorde were unique because it was the first money-making aircraft to employ hybrid circuits. The principal designer for the project was Pierre Satre, with Sir Archibald Russell as his deputy.
The Engines
To be economically feasible, Concorde needed to be able to fly long distances, and this required high efficiency. For optimal supersonic flight, turbofan engines were considered, but rejected, due to their larger cross-section which would cause excessive pull. Turbojets were found to be the best choice of engines. The engine developed was the twin coil Rolls-Royce/Snecma Olympus 593, a development of the Bristol engine first used for the Avro Vulcan bomber, and developed into an afterburning supersonic alternative for the BAC TSR-2 strike bomber.
The intake design for Concorde's engines was significant. All conservative jet engines can take in air at only around Mach 0.5; therefore the air has to be slowed from the Mach 2.0 airspeed that enters the engine intake. In particular, Concorde needed to control the shock waves that this reduction in speed generates to avoid damage to the engines. This was done by a pair of intake ramps and a secondary drop door, whose position was moved during flight to slow the air down. The ramps were at the top of the engine booth and moved down and the secondary drop door moved both up and down allowing air to flow in or out. The helpfulness of the intake system is such that, during supersonic flight, 63% of the aircraft's force is attributed to the intakes whilst the exhaust nozzles generate 29% and the engines just 8% of the thrust.
Engine Problems
Heating Issues
Beside engines, the hottest part of the structure of any supersonic aircraft is the tip. The engineers wanted to use duralumin, an aluminum alloy, throughout the aircraft due to its familiarity, cost and ease of construction. The highest temperature that aluminum could maintain over the life of the aircraft was 127 °C, which limited the top speed to Mach 2.02.
Concorde went through two cycles of heating and cooling during a flight, first cooling down as it gained height, then heating up after going supersonic. The reverse happened when descending and slowing down. This had to be factored into the metallurgical modelling. A test platform was built that repeatedly heated up a full-size section of the wing, and then cooled it, and once in a while samples of metal were taken for testing.
Due to the heat generated by compression of air as Concorde travelled supersonically, the fuselage would extend by as much as 300 mm (almost 1 ft), the most obvious symptom of this being a gap that opened up on the flight deck between the flight engineer's console and the dividing wall. On all Concordes that had a supersonic retreat flight, the flight engineers placed their hats in this gap before it cooled, where the hats remain to this day.
To keep the cabin cool, Concorde used the fuel as a heat sink for the heat from the air conditioning, the same method also cooled the hydraulics. During supersonic flight the surfaces forward from the cockpit became heated, a screen was used to deflect much of this heat from directly reaching the cockpit.
Concorde also had limitations on livery. The majority of the surface had to be painted with a highly reflective white paint to avoid overheating the aluminum structure due to heating effects from supersonic flight at Mach 2. In 1996, Air France briefly painted F-BTSD in a predominantly-blue livery (with the exception of the wings) as part of a promotional deal with Pepsi Cola. In this paint format, Air France were advised to remain at Mach 2 for no more than 20 minutes at a time, but there was no limit at speeds under Mach 1.7. F-BTSD was chosen for the promotion because the aircraft was not then programmed to maneuver any long flights that required extended Mach 2 operations.
Structural Issues
Due to the high speeds at which Concorde travelled, large forces were applied to the aircraft's structure during banks and turns. This caused twisting and deformation of the aircraft's structure. In addition there were concerns over maintaining precise control at supersonic speeds; both of these issues were resolved by active ratio changes between the inboard and outboard elevons, changing at differing speeds including supersonic. Only the innermost elevons, which are attached to the stiffest area of the wings, are active at high speed.
Additionally, the slim fuselage meant that the aircraft flexed. This was able to be seen from the rear passengers' viewpoints.
Environment Impact
The problem of the noise emitted by the powerful engines developed for Concorde by Rolls-Royce in Britain and SNECMA in France proved less tractable. It was a struggle from the start to secure approval for Concorde to be allowed to fly to and from New York, and the noise issue meant that the number of airports where it was certified to operate remained limited.
Conclusion
On 25 July 2000, Air France Flight 4590, registration F-BTSC, crashed in Gonesse, France, killing all 100 passengers and nine crew on board the flight, and four people on the ground. It was the only fatal incident involving the type
On 10 April 2003, Air France and British Airways all together announced that they would retire Concorde later that year. They cited low passenger numbers following the 25 July 2000 crash, the slump in air travel following 9/11 and rising maintenance costs.
