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.”