Supersonic: The Origins of Concorde

[In The News]

DALLAS – 28 years before two tunnel-boring machines broke through bedrock deep under the English Channel, a team of British and French engineers set to work on a no less audacious project: building a supersonic commercial aircraft.

Concorde would prove to be one of the most complex and challenging commercial aviation projects ever undertaken. We look back to the airplane’s humble beginnings on the drawing board.

France’s Sud-Aviation Super-Caravelle concept from WeirdWings

Early Years

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Britain and France were individually pursuing the idea of supersonic transport aircraft with the BAC 233 and the Super-Caravelle when, in 1962, both countries signed a treaty (not a commercial agreement) agreeing to jointly pursue Concorde.

The treaty would prove a lifeline for Concorde later on when the program was in jeopardy due to governmental revue in Britain. In the end, it was decided that violating the treaty would cost more than continuing with the development of the airplane.

While France’s Super-Caravelle was envisioned as a medium-range aircraft, Britain’s original notion was of a long-range, transatlantic capable version. After initial consultations with interested airlines, it was agreed that the design would focus on a longer-range version, and work on the medium-range French design was abandoned.

Concorde would set the stage for the current European model of aircraft production, with design, testing, and fabrication being spread among multiple sites in Britain and France.

Each country would be responsible for 50% of the aircraft with the British focusing on the front, rear, and engines and France focusing on the main fuselage and engines. British Aircraft Corporation and Aérospatiale were charged with designing the airframe while Rolls Royce and SNECMA developed the engine.

Concorde’s intake ramp system. Photo: M01 MAROT., CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=3494270

Design Challenges

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The design challenges for Concorde were considerable. While supersonic aircraft design was not new, incorporating passenger comfort and economic viability into the equation certainly was. Previous supersonic military aircraft were not sensitive to ticket prices, fuel costs, or noise pollution, but the designers of Concorde had to take this all into account.

Of initial concern, however, was what the plane would look like and how it would be powered. A balance between propulsive efficiency (how efficient the engines are) and aerodynamic efficiency and stability led to the now-iconic delta-shaped wing.

The delta wing provided Concorde with the least amount of drag at supersonic speeds and the highest level of handling during crucial sub-sonic periods, such as takeoff and landing.

Close up of engine nozzles of production Concorde F-BVFB. The nozzle consists of tilting cups. Photo: By Alf van Beem – Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=17641998

The Olympus Engine

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Designers settled on an update to the already proven engine, the Olympus, rather than a new engine design, which would have added time and cost to the program.

A supersonic version of the Olympus engine had already been built and tested on the British TSR2 aircraft, so it became a matter of updating the Olympus 320 engine to create the Olympus 593 for Concorde.

The selection of materials was also extremely important. Designers needed a metal that could withstand the heat and pressure of supersonic flight but that was also easy to obtain and machine.

After evaluating thousands of metal alloys, the aluminum alloy known as RR58 was chosen as the main body metal.

http://airways.news/wp-content/uploads/2021/09/24.02.69_Concorde_roule_et_leve_le_nez_1969_-_53Fi1869.jpgPrototype Concorde F-WTSS, taking off on another rigorous test flight in 1969. Photo: André Cros, CC BY-SA 4.0, via Wikimedia Commons

Testing Concorde

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Once materials were chosen in 1965, one of the most stringent test regimes ever for a commercial aircraft began. From static tests to flight tests, Concorde would see over four times the amount of testing that normal subsonic aircraft receive.

The peculiarities of supersonic flight also led to some of the most innovative solutions. The choice of a delta wing for Concorde also led to a long, pointed nose on the aircraft. Engineers realized that this configuration would severely diminish pilot visibility during takeoff and landing, two of the most critical phases of flight.

To solve this problem, a droop nose was designed to lower five degrees for takeoff and 12.5 degrees for landing. The nose was raised during the cruise phase of flight to ensure maximum aerodynamic efficiency.

Another puzzle for Concorde’s designers was the tension between the aircraft’s center of gravity and center of lift. On subsonic aircraft, this tension is accounted for by trim tabs and small sections on the aircraft’s control surface that adjust the aircraft’s center of gravity.

Trim tabs on a supersonic aircraft would induce too much drag so a different solution was needed. Concorde engineers solved the problem by pumping fuel during the flight between the main tanks and trim tanks located at the front and rear of the aircraft.

Concorde on an early visit to Heathrow Airport (LHR) on July 1, 1972. Photo: By Steve Fitzgerald, GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=16537166

Production Challenges

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With Concorde to be built in Britain and France, production managers needed a way to make assembly as efficient as possible. Normally, aircraft are built from the ground up in a single factory, but doing so with Concorde would result in delays in training each workforce.

BAC and Aérospatiale instead opted for a new model, one that continues to be used by Boeing and Airbus today. Large components, such as the nose and forward fuselage, arrived at the final assembly line with all components already installed, making final assembly much easier.

For Concorde (and any aircraft), weight is the ultimate enemy, so engineers sought every avenue to reduce the weight of the aircraft while maintaining structural stability. Concorde engineers opted for a process that allowed them to mill large pieces of the aircraft from single pieces of metal. This saved weight and increased the structural soundness of the airplane by decreasing the number of welds and rivets required.

Concorde 001 first flight in 1969. Photo: Fonds André Cros CC BY-SA 4.0 license by the deliberation n°27.3 of June 23rd, 2017, https://commons.wikimedia.org/w/index.php?curid=65960901

Taking to the Skies

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On March 2, 1969, Concorde 001, the test aircraft based in Toulouse, France, took off and landed, completing the Concorde program’s first successful flight and beginning six years of pre-certification testing. On April 9, Concorde 002 took off in Britain, and October 1 saw Concorde’s first supersonic flight.

Over one-third of Concorde’s flight tests occurred at supersonic speeds and a total of 5,335 flight test hours were completed in one of the most demanding flight test regimes ever undertaken.

While many airlines—including Pan American, United Airlines (UA), American Airlines (AA), Qantas (QF), and Middle East Airlines—had placed orders for Concorde, only two companies, British Airways (BA) and Air France (AF), ever finalized those orders and took delivery.

On January 21, 1976, BA flew the first commercial service from London to Bahrain, while AF flew from Paris to Rio de Janeiro. Concorde first visited Washington and soon expanded service to New York.

The development of Concorde proved that supersonic transport was possible, but perhaps more importantly, lessons from Concorde have influenced a generation of airframers and engine makers’ design and production processes.

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Featured image: Concorde landing at Farnborough in September 1974. Photo: By Steve Fitzgerald – http://www.airliners.net/photo/British-Aircraft-Corporation/Aerospatiale-BAC-Concorde/1804269/L/, GFDL 1.2, https://commons.wikimedia.org/w/index.php?curid=16537090

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