Science

How Concorde Pushed the Limits – Then Pushed Them Too Far

Flying at twice the speed of sound five miles higher than a 747, it was billed as the future of air travel. Yet in the fiftieth year since Concorde’s first flight, it’s over fifteen since its last. Thursday, 5 September 2019

By Ben Barry
The most iconic feature of the aircraft, Concorde's delta wing design allowed for devastating speed – but required great thrust to combat drag to get airborne. Takeoffs were often accompanied by vapour rising from the wings.

Fifty years ago – as Apollo 11 was reaching for the moon – across the Atlantic an airborne revolution of a different kind was taking place.

On 2 March 1969, the prototype Concorde 001 embarked on its maiden flight from Toulouse. The new 100-passenger plane was a supersonic marvel that put Britain and France at the cutting-edge of aviation technology: a commercial aircraft capable of flying from London to New York in just under three hours at up to Mach 2, or 1350mph. The joke was, due to the timezone-challenging speed, you’d arrive before you left. But sonic booms, disappointing sales, stratospheric costs and the fatal crash of Air France flight 4590 would all clip its wings. 

Post War Innovation

Concorde’s genesis can be traced back to the late 1940s and 1950s, when aviation technologies developed for the Second World War gave Britain a lead of at least five years over Russia and the US – with its greatest expertise of all relating to jet engines. Post-war, this know-how was quickly adapted for commercial aircraft, with the British-built de Havilland Comet the world’s first commercial jet airliner in 1949.

Supersonic technology had already been developed for fighter jets, with the American rocketplane Bell X-1 first breaking the sound barrier in 1947. Later, the English Electric Lightning become the world's first jet capable of Mach 2, and 'supercruise' (sustained supersonic flight with a payload, and without the constant use of afterburners) achieved in 1958 – an ability that would be intrinsic in the concept of Concorde.  

British engineers began working on supersonic passenger travel as the next logical step, but projected development costs of £175m (over £3.5bn today) were prohibitive. French company Sud Aviation was simultaneously pursuing the same goal with its Super Caravelle, however, and had independently conceived a similar design faced with identical challenges. An Anglo-French partnership would allow supersonic passenger travel to be developed more affordably, and the two governments signed an agreement in 1962; Concorde means agreement, harmony or union.

Afterburners were essential for getting Concorde through the sound barrier. The enormous consumption of fuel was one of Concorde's downfalls – as fuel prices rose, profitability fell.

Concorde’s Concept takes Flight

The finished design featured a 62-metre-long aluminium fuselage with wings arranged in an ogival delta design that flowed like a long cloak, beginning around a quarter of the way down the body and reaching a maximum 25-metre span where the long tail fin began its gradual ramp upwards. The delta-wing design balanced the requirement for sustained supersonic flight with lower-speed manoeuvrability during take-off and landing.

The wings incorporated most of the fuel tanks (tanks 9, 10 and 11 were in the fuselage and tail), which the flight engineer – sitting behind the captain and first officer –  would actively manage to balance the plane.

Four Rolls-Royce/SNECMA Olympus 593 engines were mounted on the underside of the wings, two per side. Developed by Bristol Aero Engines, the Olympus 593 was the world’s first two-spool axial flow turbojet engine, and used a French-manufactured afterburner. Renowned for thermal efficiency at high thrust, each engine produced 32,000lb of force without afterburner ‘reheating’, or 38,000lb with; the afterburners were essential to break the sound barrier. 

Concorde being constructed in the British Airways production hangar at Filton, Bristol.

But the biggest breakthrough of all related to the computer-controlled, variable-geometry intake system. Its moving ramps and doors ensured steady subsonic airflow at all speeds. This worked so well that during Mach 2 flight, the intakes alone produced 63 per cent of forward thrust.

Put to the Test 

Britain took responsibility for the majority of engine production (first BAC, later BAE systems), France for the majority of fuselage production (first Sud Aviation, later Aérospatiale, finally Airbus). Simulation could only test so much. Final development involved what must have been daunting flights conducted mostly over water in prototypes fitted with escape hatches, the pilots wearing parachutes as they verified Concorde behaved as expected.

Following the first French test flight on March 3 1969, British test pilots first flew Concorde prototype 002 on April 9, from Filton, Bristol. Further milestones were reached when the aircraft achieved Mach 1 – supersonic flight – on October 1. The following November, in 1970, both prototypes flew at Mach 2. It would be 1976 before the production Concorde fleet commenced commercial flights.  

The project ultimately totalled £1.3bn – close to £8bn today – and was funded by UK and French taxpayers, with state-owned airlines British Airways (BA) and Air France running Concorde as an assured minimum once development was complete. Initially, there were over 200 orders, but the fuel crisis of 1973 more than doubled the cost of aviation fuel, and only 14 of the 20 built ever entered commercial service – with Air France and British Airways the aircraft's sole operators. It makes the few pilots who flew Concorde part of a highly elite club.

Concorde's first flight crew: (left-right): Captain André Turcat, co-pilot Jacques Guignard, flight engineer Henri Perrier and mechanic Michel Retif. The maiden flight of Concorde 001, on March 2 1969 , lasted 29 minutes at a leisurely 298 mph. The British equivalent, Concorde 002, completed its 22 minute maiden flight a month later on April 9th.

“40 or 50 per cent of senior captains failed. They’d been World War Two Lancaster pilots, very capable, but they couldn’t get their brains going to cope with it.”

John Hutchinson, Concorde Captain

On the Flight Deck

John Hutchinson captained Concorde from 1977 to 1992, after flying the Boeing 707 and 747, and becoming captain of the Vickers VC10 in January 1976. He bid for Concorde in the spring of 1977. ‘I was 40 years old, I’d been captain for 15 months, I put my name in, and to my utter astonishment I was selected,’ he told National Geographic UK. ‘There’d been two training courses previously, and around 40 or 50 per cent of senior captains failed. They’d been World War Two Lancaster pilots, very capable, but they couldn’t get their brains going to cope with it. So when it came to the third course, all these senior captains said “stuff that for a game of soldiers”. That opened the door for me, but it was seriously hard graft.’

A normal training course to fly new aircraft lasts 8 weeks, but Concorde more than tripled that to 28 weeks, with original test pilots including John Cochcrane, Peter Baker and Brian Trubshaw overseeing the gruelling induction process. The residential course included two months’ technical instruction, and at least 76 hours flight simulator training. Circuit work followed, with the trainees repeatedly landing and taking off. For successful candidates, the final hurdle was two months’ supervision on passenger flights. 

Concorde's aerodynamic silhouette was immediately recognisable from the ground. Here seen in its final flight, leaving Edinburgh airport, in October 2004.

But Concorde was not, remembers Hutchinson, a difficult aircraft to fly – and the analogue instruments made the flight deck relatively familiar. ‘It did exactly what you wanted, you could trim it up with your thumb and forefinger, it was a proper thoroughbred and extremely easy to fly. But it could be very tricky to operate – you’d be doing twice the speed of sound across the Atlantic, and if you had an engine failure you needed to absolutely know your stuff. Concorde does not take prisoners.’

Mike Bannister also flew Concorde from 1977. He remembers going straight to 4,000ft on his first training flight when his training captain had asked him to level off at 2,000ft, so potent were Concorde’s engines. But familiarity came quickly, and Bannister still vividly recalls the flight procedures leaving Heathrow on his way to JFK airport, New York.

A test crew at work on Concorde. Streamlined and surprisingly small compared to a subsonic aircraft, space was a sacrifice for speed.

“At 1350mph the aluminium fuselage expanded by as much as ten inches due to kinetic heating – most noticeably leaving a gap between the rear edge of the flight engineer’s panel and the bulkhead. ”

‘We’d take off with the afterburners to get up quickly and minimise noise [on the ground, though Concorde was controversially exempt from Heathrow’s usual noise limits], just a minute and ten seconds, then reduce power. We’d [use] full climb power up to 28,000 ft at Mach 0.95, then south east of Swansea over the Bristol channel we’d switch on the four afterburners in pairs, to minimise spilling the passengers’ drinks!’

With no noise or ‘thump’ noticeable on-board, the only tell-tale for the pilots was the vertical speed indicator briefly going haywire, while passengers would feel acceleration ‘like a fast sports car dropping a gear’, says Bannister.

Concorde was now pushing a kind of three-dimensional bow-wave of air. Below Mach 1.3, this would dissipate in the atmosphere, but Concorde could ‘supercruise’ at Mach 2, twice the speed of sound, causing a noise like a thunderclap to be heard on the ground. It was why Concorde mostly flew supersonically while crossing water, and had a limited number of regular destinations that were rarely notably distant from the coast. These were Paris Charles de Gaulle or London Heathrow to New York, Barbados, Washington and Miami – though Concorde's simultaneous first ever commercial flights in 1976 were from Heathrow to Bahrain, and Paris to Brazil. 

Concorde at takeoff.

Fierce speed – at a cost 

Concorde could not escape the physics of sonic booms, but it was unique in being able to accelerate from Mach 1.7 to Mach 2 without afterburners. While it burned fuel at approximately twice the rate of a 747-400 at an average of 25,629 litres per hour, this so-called supercruise strategy allowed this leg of the flight to actually be more efficient, and roughly half the 80 tonnes of fuel required for the flight from London to New York were burnt during take-off and acceleration up to Mach 2. Noise and other environmental concerns also saw protests at some runways.

At it’s peak groundspeed of 1350mph, Concorde was covering 22.5 miles per minute at 60,000 ft, and the aluminium fuselage expanded by as much as ten inches due to kinetic heating, most noticeably leaving a gap between the rear edge of the flight engineer’s panel and the bulkhead. 

Screens at the front of the passenger compartment displayed the Mach number, altitude and temperature. Meanwhile, outside the cabin champagne was served and (in earlier days) smoke from complementary cigars filled the cabin.

In 1972 demonstrators greeted the Concorde as it arrived at Sydney airport. The aircraft's sonic boom when it broke the sound barrier was hugely loud on the ground even from 60,000ft, causing both environmental and cultural disturbance. For this reason many of Concorde's sonic booms were over the ocean.

‘We really would fly the movers and shakers, and in those days we had an open flight-deck,’ remembers Hutchinson. ‘I’d look down the list to see who was on-board, and if there was someone I wouldn’t mind meeting, I’d send an invitation to watch take-off and landing from the cockpit – Muhammad Ali, Paul McCartney and Elvis Costello all spring to mind, wonderful.’

Meanwhile, six cabin crew worked furiously – unable to serve passengers during take-off and landing, they typically had around 2 hours 30 minutes from London to New York to provide a full drinks and meal service, which Bannister describes as ‘like First Class Plus’.

Despite the prohibitive development costs – born by the tax payer – Concorde could be operated profitably, and in the late 1980s British Airways’ fleet of seven Concordes made a third of company profits. ‘Ticket costs were not a factor,’ recalls Hutchinson. ‘In the late 1980s BA conducted surveys of regular passengers, asking how much they paid. And people hadn’t a clue, their PAs booked the tickets. So they’d say “I don’t know, £4000, £5000?”, and BA would average it out and that’s what they’d charge. It was a fantastic money-maker.’

The old-school controls of Concorde betrayed the heritage of the aircraft's futuristic design.

“It was extremely easy to fly. But it could be very tricky to operate – you’d be doing twice the speed of sound across the Atlantic, and if you had an engine failure you needed to absolutely know your stuff. Concorde does not take prisoners.”

John Hutchinson

Disaster and Aftermath

But the fatal Air France flight on 25 July 2000 was a disaster from which Concorde was never to recover. The chain of events began when flight 4590 ran over a metal strip dropped on the runway by another aircraft. The metal punctured a tyre, sending 4kg of rubber into the underside of the left wing. This impact sent a shockwave through the fuel tank, which ruptured from inside out. Fuel ignited from a spark from wiring in the undercarriage. It was too late to abort take off, and flight 4590 crashed into a hotel while trying to divert to nearby Le Bourget airport. 113 people died: all those on board, plus four on the ground.

If the consequences were catastrophic, they could have been worse – the stricken and veering Concorde came within a reported 20ft of an Air France 747 on the runway with President Jacques Chirac aboard. Which meant the French government’s great aviation project could have compounded a disaster by killing its serving president at an airport named for its greatest leader.

Hutchinson maintains that Concorde was always airworthy, and that the crash should never have happened. ‘As with all air accidents, it was a combination of factors. During maintenance, an undercarriage leg had been stripped and rebuilt, but they forgot to put a spacer back in, which kept the two sets of wheels in proper alignment. Without the spacer it was like a shopping trolley wheel, and that’s why the pilots couldn’t control it [on the ground].”

The official investigation ruled the spacer to have not been a factor in the crash, and stated that even without the subsequent engine malfunctions and loss of thrust – along with additional potentially aggravating factors, such as the aircraft carrying excess weight and the presence of a tailwind – the ‘damage caused by the fire to the aircraft’s structure would have led rapidly to the loss of the aircraft.’ Many still maintain compound causes, including operational error, made the crash inevitable. 

News of Air France flight 4590 breaks on the cover of the Daily Telegraph, July 26, 2000. The incident grounded both British and French Concorde aircraft pending safety modifications.

Post-accident, Air France and BA both grounded their aircraft, but after a few days BA introduced special procedures pending full analysis of the crash, and began flights again. Flights continued for several weeks until a ruling by the Civil Aviation Authority – to comply with a similar decree over the channel – ceased operations pending a suspension of airworthiness and a full safety review. This came into such sudden effect that a Concorde flight to New York had to cease its taxi and return to the terminal.

Gallery: Concorde's History in Pictures

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Bannister consulted on modifications that saw Concorde return to service in November 2001 – Kevlar in the tyre carcasses and fuel tanks, and additional armoured protection for the undercarriage. ‘Any of those three things would have stopped the accident,’ he says.

Both airlines resumed flying Concorde, but the second Iraq war further fuelled Concorde’s downfall. Costs to keep the aircraft in service rocketed – from £18m a year in the 1980s before a plane turned a wheel, to around £60m by 2002. That was likely to increase to £100m.

It was unsustainable. France stopped flying Concorde in mid-2003, and British Airways’ last commercial Concorde flight touched down on October 24 2003 – piloted by Mike Bannister. ‘From the moment the retirement date was announced, I decided those final flights should be a celebration, not a wake. But I remember after the very last flight there was a reception at BA. I was last to leave, it was foggy outside and there were five perfectly serviceable Concordes all sitting there under neon lights, and I have to admit there was a tear in my eye.’

In the 16 years since Concorde's final flight, various startups – as well as established aviation corporations – have been working on the next supersonic airline concept. The Boom Overture is one of the proposed new breed of supersonic airliners – and the most reminiscent of Concorde's 50 year-old design.

To the Future and Back

A few years ago, there was some hope of returning Concorde to very limited service – air shows and pleasure trips, perhaps – but Bannister believes this to be no longer realistic. Even his most optimistic estimates for running a single plane are £1m per week before a plane even moved, and the issues around infrastructure, engineering and ground-staff support and pilot training are perhaps more significant still.

Supersonic commercial travel could be about to make a comeback, however, with three American firms – Aerion, Boom and Spike – developing new designs. Bannister is most impressed by the Boom Overture, which plans to carry 55-75 passengers at up to Mach 2.2. The company intends to fly a one-third-scale prototype in early 2020.

The new aircraft’s use of modified existing engines – despite lacking afterburners – have provoked environmental concerns, however, with the International Council on Clean Transportation saying the engines will exceed global limits for new subsonic jets by 40 per cent for NOx and 70 per cent for C02.

It’s not only the engines that will be familiar, and for Hutchinson, the designs themselves echo those of half a century ago.

‘It fascinates me to look at the new designs for supersonic jets,’ he says. ‘The guys in the late 1950s and 1960s were playing around with models in the wind tunnel, and yet these new designs are very similar despite all the advances in technology. It just proves how absolutely spot on Concorde’s design was 50 years ago.’