The Concorde Redemption | Flight Today | Air & Space Magazine

The Concorde Redemption

Can the superplane make a comeback?

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As Concorde Prototype 001 swiftly accelerated and rotated off the runway at Toulouse-Blagnac airfield, an odd scene was taking place just outside the perimeter fence: Many in the crowd were not just watching the Concorde’s maiden flight, they were cheering “Allez France! Allez France!” as if they were watching France score a goal in an international soccer game. When the airplane landed 35 minutes later after a subsonic flight, it was clear not only that aviation history had been made on March 2, 1969, but also that France had a proud new symbol. As the Paris newspaper Le Monde once noted, Concorde “was created largely to serve the prestige of France. [It was] the expression of political will, founded on a certain idea of national grandeur.”

Thus the national trauma that gripped France last summer. At 4:44 p.m. Paris time on July 25, 2000, with pilot Christian Marty and copilot Jean Marcot at the controls, Air France Flight 4590 blew a tire on its left main gear on takeoff from Charles de Gaulle airport. As the crew fought to keep the airplane under control, it began drifting left on Runway 26R with a long sheet of flames trailing from its left wing. The alarm gong sounded in the cockpit, and engines one and two, of four, lost power. “Watch the airspeed, the airspeed, the airspeed!” Marcot yelled to Marty as the airplane continued heading left, in the general direction of a taxiing Air France 747 bringing President Jacques Chirac back from a summit in Tokyo.

Marty tugged on the controls and tried for liftoff at 188 knots, 11 knots below normal rotation speed. With thrust coming from only its two right engines, Flight 4590 struggled barely 200 feet into the air, then suddenly went nose up, rolled over, and crashed onto a hotel. All 100 passengers, mainly German tourists heading for a rendezvous with a cruise ship in New York, were killed, along with the three flight crew members, six flight attendants, and four people on the ground.

Said France’s largest newspaper, Le Figaro, “Without doubt, Concorde died yesterday at the age of 31. All that will remain is the myth of a beautiful white bird.” Comparing the crash to the sinking of the Titanic, the Hindenburg bursting into flames, and the Challenger space shuttle exploding, London’s The Times lamented, “Nothing will ever be quite the same again…. This was the superplane, the symbol of progress, the icon of invention, a totem.”

Air France president Jean-Cyril Spinetta, standing in his office by a picture window overlooking Charles de Gaulle’s runways, watched, horrified, as Concorde F-BTSC trailed flames and crashed. He immediately grounded the company’s Concorde fleet until further notice.

Like many, Spinetta thought he knew what went wrong. “For all of those who were eyewitnesses to this catastrophe, and I am one of them,” he said later, “the cause was an engine fire on takeoff.” But was it?

British Airways initially followed Air France’s lead and grounded its Concordes, then resumed service the next day. But the French company heeded Transport Minister Jean-Claude Gayssot, who declared that the airplane would not fly again until the accident was fully explained. Franco-British discord continued until August 16, when France’s Bureau Enquêtes Accidents (BEA) declared that, contrary to Spinetta’s impression, a tire blowout caused the crash.

It also took the rare step of recommending suspension of Concorde’s certificate of airworthiness. France’s Direction Générale de l’Aviation Civile (DGAC), the equivalent of the U.S. Federal Aviation Administration, pulled the certificate, and Britain’s Civil Aviation Authority went along. CAA Chairman Sir Malcolm Field explained: “What is uniquely different in this case is that tire debris alone is thought to have led to this catastrophic accident.” With that, BA stopped one Concorde as it was about to take off from Heathrow, and ferried another back from New York without passengers.

Two official French inquiries were set in motion. The BEA searched for causes, while a judicial investigation headed by three magistrates tried to determine legal responsibilities. As the investigation dragged on for months, Britain’s Air Accidents Investigation Branch, which participated in the inquiry under terms of a long-standing Franco-British agreement on Concorde safety incidents and was eager to keep the investigation moving, officially protested against “unacceptable procedural delays” in France, to no avail.

The first puzzle to solve was a piece of the number five fuel tank found on the runway that somehow had been torn loose from the inside out. Researchers from European Aeronautic Defense and Space Co. (EADS), successor to the original French Concorde builder, Sud-Aviation, ran a computer simulation that came up with the answer: When a large piece of tire weighing about nine pounds struck the underside of the left wing, the impact generated a shock wave, propagated through the full tank of jet fuel, that moved first up, then down, exploding outward. The resulting one-square-foot hole created a massive kerosene leak—on the order of 20 gallons per second—that somehow ignited.

Why was there such a large chunk of tire, bigger than usual, after a blowout? Investigators found a 17-inch piece of titanium on the runway, a thrust reverser wear strip from an airliner that had taken off minutes before Flight 4590. Striking it at high speed, they theorize, the number two tire was scalped of a five-foot length of tread, which was whipped up at the wing by tremendous centrifugal force, producing the shock wave.

But the most controversial finding concerned a spacer that normally holds two lateral rings in position on the oleo/bogie coupling of the left main gear and is vital to wheel alignment. Apparently because of an Air France maintenance error, the spacer was not reinstalled after routine maintenance work performed four days before the crash, the BEA preliminary report says. Nonetheless, the BEA ruled out the missing spacer as a cause of the crash. (Air France, which sources close to the investigation say has been “traumatized” by the crash, and which was sued for some $100 million by families of the crash victims, declined repeated interview requests for this article.)

“The truth is that because of that missing spacer, the left main gear was slightly skewed on the takeoff roll. Skidding heated and wore down the tire, caused the plane to drift to the left side of the runway, and kept it from accelerating normally,” charges Jean-Marie Chauve, a 37-year Air France veteran and retired Concorde pilot who has done his own calculations—and had them verified by independent experts—based on published information from the flight data and cockpit voice recorders. His version is seconded by Michel Suaud, a longtime Concorde flight engineer who is now retired. They spent several months preparing a detailed report on the crash, which they have presented to the investigating magistrate of the judicial inquiry.

“Our figures show that the plane was moving to the left at the start of the takeoff roll, not just after the blowout and loss of engines one and two,” Chauve says. “The tire burst at around 174 knots and only after the blowout did it strike the metal strip. If acceleration had been nominal, the plane would have been airborne about 50 yards before reaching the strip. The BEA says the leftward yaw was caused by loss of thrust from the left engines, not by the skewed bogie. But they’ve never shown us where our figures are wrong. They are under pressure to make this look like a freak accident caused by that piece of metal on the runway. That would cover up Air France’s fault in letting a plane take off that wasn’t ready.”

Asked about this, BEA chief Paul-Louis Arslanian responded: “It’s true that, due to a regrettable maintenance error, the spacer had not been replaced. But our investigation shows that its absence, though it slightly affected alignment of the left gear, had no influence on the way the tires were worn, or on the plane’s trajectory and acceleration.”

The argument may never be settled to everyone’s satisfaction. Meanwhile, the DGAC and CAA called in the original Concorde builders, BAE Systems, successor to British Aircraft Corporation, and EADS Airbus, along with the original Olympus engine manufacturers, Rolls-Royce and Snecma. If Concorde were to fly again, they would have to keep that kind of accident from happening. (French and British regulations do not require waiting for results of the investigation to begin modifications, or even for the airlines to resume service.) Says Gérard Le Houx, a DGAC official in Paris: “We told them there are three general problem areas: reinforcing the plane’s structure, mainly the fuel tanks, preventing such a fire, and ensuring the engines are not affected by fire when there’s a fuel leak. Once they give us those solutions, we can consider restoring Concorde’s certificate.”

With the airlines pushing to resume service, the companies assigned some 100 engineers to the top-priority project. “At first we and EADS Airbus talked with the authorities about all sorts of modifications, feeling our way, pushing forward on a number of fronts,” says Howard Berry, an official at BAE Systems. “What we had to do was somehow break the chain of events that occurred in the crash. The time scale [for completing the modifications] has been unpredictable because we’ve been going down a number of avenues and have to take into account any test results and the accident investigation.”

Besides the technical challenge, there was an economic one: The modifications must not unduly increase the airplane’s empty weight or reduce payload or maximum range, any of which would make it more costly to operate. And time was of the essence: Every month the Concorde fleets were grounded cost the two operators millions of dollars in lost revenue, continuing maintenance, salaries for inactive air crews, and, possibly, long-term loss of passengers.

From the start, British Airways was more optimistic about getting Concorde back into service than Air France. “That’s normal,” says Claud Freeman, BA Concorde manager at London’s Heathrow Airport. “After all, Air France management saw it happen right in front of their offices. Had we not taken a very positive attitude immediately, I believe Concorde probably would have stopped flying for good.”

The engineers felt the pressure; they were not only modifying an aircraft but trying to save an icon, a super-sleek machine that travels at Mach 2, faster than a rifle bullet. The roughly 150,000 Concorde passengers a year have gladly paid some $10,000 for a round-trip transatlantic ticket to race the sun, leaving London or Paris for New York and arriving a few minutes before they left (fastest crossing on record: two hours, 52 minutes, 59 seconds in February 1996, New York to London). As BBC interviewer Sir David Frost, who has made over 200 trips on the airplane, has said, “Concorde is the only way I know that you can be in two places at the same time.”

Not bad for an aircraft designed when engineers still used slide rules and log tables to figure out supersonic aerodynamics. Concorde’s engineers created a radically different bird that operates in a weird environment. At Mach 2, about 1,322 mph, and 60,000 feet, the air temperature is around –67 degrees Fahrenheit, but atmospheric friction heats the fuselage skin to the boiling point of water, expanding the metal and making the airplane about half a foot longer. “Concorde is a triumph of engineering,” says John Anderson, a curator in the aeronautics division of the National Air and Space Museum. “Particularly the wing, which is very complex in shape with lots of curvature for low drag and good stability. And they did it all without computers.”

Today, however, its flight deck instrumentation is old technology, the equivalent of a first-generation 747. Concorde pilots laboriously read electro-mechanical dials instead of glancing at the comprehensive, computer-generated displays of contemporary glass cockpits. “It’s not an easy plane to fly. You have to be constantly alert,” says Peter Duffey, a retired British Airways Concorde pilot and author of Comets and Concordes. “Things happen more quickly. For example, its takeoff time is only half that of a 747. At Mach 2, about 22 miles a minute, you’re always thinking about where you can land in an emergency, and there are about 50 reasons besides engine failure why you would have to take it down to subsonic flight. Unlike a conventional transatlantic run, you’re not sitting there for seven hours wondering what to do with yourself.”

Its makers never got around to modernizing Concorde’s cockpit because not enough were sold to make updating it economical. After the French and British governments sank several billion dollars in development costs in the 1960s, the only takers were their two captive, state-owned national carriers. As early as 1965, Beverly Shenstone, the technical director of BOAC, the predecessor of today’s British Airways, warned that Concorde was “the largest, most expensive, and most dubious project ever undertaken in the development of civil aircraft.”

Only 20 Concordes were built, including prototypes and pre-production models; 14 entered service. Because Concorde’s development costs were footed by taxpayers, both British Airways and Air France have claimed in recent years that their supersonic flagship was making a slim profit—in Air France’s case, reportedly only about $3 million, or a minuscule 1.3 percent of its total annual profits. “The economics of Concorde never made sense and there was never a market for it,” contends Ron Davies, curator of air transport at the National Air and Space Museum. “For every hour it spends in the air, it spends 14 on the ground. And for every seat transported across the Atlantic, it has to carry one ton of fuel—two tons if it’s only half full, which often happens. It’s so inefficient it’s unbelievable.” And all that development money spent? “Taxpayer-funded executive air transport,” Davies says. “It’s one of the biggest scams ever perpetrated. Concorde’s days are numbered and all they’re doing now is prolonging the agony.”

Last year’s crash shocked the world. Yet the omens had long indicated that not all was well with the beautiful white bird. The very day before the crash, Air France discovered cracks in the wings of four of its six aging Concordes (though not in the one that crashed). This followed British Airways’ finding cracks, like those at Air France, termed non-safety-critical, in all seven of its airplanes; it grounded one for repairs just before July 25.

Perhaps more ominous is the long series of incidents and warnings that came to light as crash investigators and the media delved into Concorde’s past. For example, aircraft belonging to both companies had lost parts of their elevons and rudders several times in flight but were able to land safely. In 1998, the Olympus 593 engines were found to have 152 problems in hardware design or other factors, 55 of which were considered “significant risks,” and BA and Rolls-Royce initiated a plan to remedy them. The engine study warned, “A major technical event would probably end Concorde operation.”

But the scariest scenario to come out this year has been the BEA’s list of 57 tire-related incidents from 1976 to 2000, 30 of which were on Air France flights and 27 on British Airways. Of those, 32 blowouts damaged the aircraft’s structure, engines, or hydraulics, and six resulted in penetration of one or more fuel tanks.

The worst of these occurred on June 14, 1979, when Air France Flight 054 to Paris blew the two rear tires on its left main gear on takeoff from Washington Dulles Airport, hurling high-speed rubber and wheel rim debris at the left wing and engines. The flight crew knew about the blown tires and were diverting to New York, but they were unaware of the true extent of the problem until a passenger convinced the mostly indifferent cabin attendants to bring a crew member back to examine a 12-square-foot hole in the top wing skin. “I took the gentleman who had come back from the flight deck to my seat and virtually held his head to the window so that he could look down and see the hole in the wing,” the passenger wrote in his harrowing statement to the National Transportation Safety Board (available at www.airspacemag.com). “When he saw the hole, he exclaimed, ‘Mon Dieu!’ ” The crew managed an emergency landing at Dulles with Jet A1 streaming from a dozen holes in fuel tanks, damage to the number two engine, severed electrical cables, and the loss of two of three hydraulic systems. Following recommendations from the NTSB, the FAA urgently telegraphed airworthiness directives to both Concorde operators detailing procedures for more intensive checks of tires, wheels, and brakes.

The airplane was later modified to include roll-on wheel rims, strengthened tires, and a tire failure warning in the cockpit. But even after the NTSB’s then-chairman, James B. King, wrote to his French counterpart on November 9, 1981, expressing “serious concern” about “the repetitive nature of these incidents,” they continued. As another former NTSB chief, Jim Burnett, points out, “Concorde could have been certified with a design flaw nobody noticed at the time. If there were as many Concordes flying as 737s, I suspect that we would have seen this kind of accident many times.”

Will the current modifications solve the problem for good? Because EADS Airbus is responsible for the wings, it has taken the lead in trying to find the solution. Its engineers quickly focused on modifications to the fuel tanks to cut the risk of fire from a fuel leak, and armoring electrical cables, which were suspected of igniting the fire with a spark, in the airplane’s wheel wells.

Armoring the wiring was the easy part. It was shaped into “looms” of 15 to 20 cables each, the main one going to the brake cooling fans. These were then protected with braided stainless steel and Teflon, rather than the aluminum tubing used before. To protect the fuel tanks, engineers decided on flexible liners of Viton, a heat-resistant rubberized sealant, and Kevlar, a material used in bulletproof vests. Five times stronger on a weight basis than steel, the thin sheets of Kevlar are sandwiched between layers of Viton. The liners, the reasoning goes, will reduce any shock wave that would be produced by debris and limit the flow of fuel by being sucked down into a hole.

Still, this sort of modification has never been tried before on an airliner. If the theory is simple, the execution is enormously complex. “The liners are actually in the form of 102 shallow trays that go into six fuel tanks, depending on their proximity to the wheels,” explains Claud Freeman,  working at the Heathrow hangar on Alpha Foxtrot, the first Concorde to receive the modifications. “Concorde was in effect hand-built, with each one slightly different, so each liner is custom molded to achieve the exact shape and size. We have to keep them separate from the wing skin, because circulating fuel keeps it cool at supersonic flight. That’s why the liners’ sides are attached to some 5,000 separate attachment brackets bolted to wing spars. Because the fuel can’t flow as freely as before, this will create about 880 pounds of additional unusable fuel. We might have to take out a row of seats.”

The modifications were done by teams of 40 engineers working two eight-hour shifts a day. “It’s work for engineers on a diet,” quips Denis Morris, a project manager in the Concorde division. “First they have to squeeze through these oval access holes in the underside of the wing, then crawl through the inside of the wing all the way out to the end, where there’s only barely enough space to work.”

Although not strictly part of the airplane’s recertification efforts, new tires being developed by Michelin are supposed to mitigate the blowout problem. Radial models banded with an aramid composite similar to Kevlar, they are expected to better resist bursting; if they do blow out, they should break up into smaller pieces less likely to hit the fuel tanks. They are also expected to be about 44 pounds lighter than the previous ones, meaning a total saving of 352 pounds—helping offset the weight increase due to the liners.

Can Concorde come back? “I have always said that Concorde would fly again,” French Transport Minister Gayssot has declared. Media leaks in Paris had Air France laying plans for a resumption of service in September or October. British Airways, which is spending nearly $25 million to modify the Concorde, was poised to proceed faster, assuming the CAA restored the certificate of airworthiness, and was betting a further $20 million worth of refurbishing on the fleet’s cabins, including new lighting that turns blue as Concorde hits Mach 1. (Air France hasn’t released its costs, but has indicated that it has set aside $11 million for costs related to resuming service.) Says Les Dorr, spokeman for the Federal Aviation Administration: “We would accept the certification of the CAA and the DGAC, unless there were some obvious issues that gave us reason to disagree with them or suspect the aircraft was unsafe.”

Should Concorde come back? “If they get the modifications worked out and the certifying authorities are satisfied the plane is safe, then why not?” says Frank Taylor, director of the Aviation Safety Center at Britain’s Cranfield University. “Given the relatively small number of flying hours it puts in and the great amount of maintenance attention it gets, its age should be no problem.”

Former NTSB chief Jim Burnett has some doubts. “I would love to see Concorde fly again,” he says. “But this accident reminds us that if it fails, a plane poses a risk not only to those flying it but also to people on the ground. All of us in aviation safety know the greatest risks are on the runway, during takeoff and landing, and that’s where Concorde has had the most problems.”

When the airplane entered service in 1976, its lifespan was to be 6,700 flights, which would have dictated ending operations around 1993. Since then, structural modifications, changes to inspection and maintenance programs, and other alterations have extended that to around 2010, depending on usage. But Concorde’s comeback is not just a question of technology. Just as there were 30 years ago, intangibles like prestige are at stake. And it’s still a marketing tool in a very competitive arena. As Rod Eddington, British Airways chief executive, says, “It’s one of the few things in this business where one airline enjoys a unique sustainable advantage over another.”

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