Fragmenting Tire Dooms Supersonic Concorde (Paris-CDG, 2000)

“Five-star airliner crashes on two-star hotel”

The Anglo-French supersonic Concorde, the most glamorous and most beautiful airliner ever, stirred the hearts of the public in France and the UK, who had paid out so much in taxes to support it and its mostly wealthy passengers.

Air France Flight 4590, July 25, 2000

Concorde’s History

The world’s first supersonic airliner, the Concorde 001, rolled onto the tarmac in 1967, but according to CNN it took two more years of testing and fine-tuning of the powerful engines before it made its maiden flight over France on March 2, 1969. The original plan was for a production run of three hundred, but in the end it was limited to just fourteen. Air France cannibalized one of those for spare parts in 1982, and another crashed, leaving five for Air France and seven for British Airways when the two airlines withdrew Concorde from service in 2003.

These days the authorities would never certify such a noisy bird, so Concorde was surviving on the certificates issued in the 1970s. Even then the United States would not approve inland flights, so its regular scheduled flights to the States were mostly to the East Coast, and New York in particular. Some said it was sour grapes at being beaten to the post on the part of the United States.

When Concorde finally entered airline service, it was a Pyrrhic victory for its makers or, rather, the two nations of taxpayers who provided such generous funding. Key countries on major overland routes refused to allow it to pass over their territories. For timesaving reasons, it was essential to fly overland, as the aircraft did not have the range to fly the long routes over the Pacific Ocean. Finally, the fuel-guzzling Concorde had the misfortune to come on the scene just as fuel prices were skyrocketing.

The majestic Concorde mainly benefited the rich and famous, though many found first class on a conventional aircraft to be preferable to the cramped seating on Concorde. Some celebrities, such as the British TV personality David Frost, were virtually commuting between London and New York on Concorde. Not so well known is the good use courier companies, such as DHL, put it to in delivering documents and financial instruments for major companies when time really was money. Even so, not enough demand existed to employ fully even that tiny fleet.
Air France had more difficulty filling seats than British Airways, who made a healthy profit out of it. Not only was this because more top business people and celebrities fly to London but also partly because London is nearer than Paris to New York and Washington—quite significant with an aircraft operating near the limit of its operating range. Air France used charter flights and excursions to help fill those seats.

The Fatal Flight

Indeed, the flight that was to last only a minute or two before ending in disaster just after taking off from Paris’s Charles de Gaulle Airport in July 2000 was just such a charter flight. It carried elderly Germans to New York to join a luxury Caribbean cruise.

Concorde spooled up its engines to take off with its long beak tipped five degrees downward and pointing just in front of another Air France aircraft, which had brought the French president and his wife back from an official visit to Japan. (The nose usually droops down five degrees for takeoff, and twelve-and-a-half degrees on landing, so the long nose does not obscure the pilots’ view.) Though slim and elegant, the Concorde was almost certainly overweight, with fuel representing just over half her total weight.

The captain thought they had an all-up weight (AUW) of 185,100 kilos, placing them, he said, at the aircraft’s structural limit. He did not know this was an underestimate and did not include nineteen items of baggage loaded at the last minute. It is also likely that the unburned fuel in the rear tank and the nineteen extra items of luggage had moved the center of gravity too far aft.

Much to the surprise of the BEA (Bureau d’Enquêtes et d’Analyses, the French Air Accident Investigation Bureau), the announcement by the control tower of an eight-knot tailwind did not elicit any comment from the aircrew. At the very least, the captain should have considered taking off against the wind. Although a wind of eight knots may not seem much, taking off in the opposite direction would mean sixteen knots less groundspeed. Because of limitations on the maximum speed for the tires, a tail wind of eight knots meant they were too heavy.

An article in the British Sunday newspaper the Observer, written by David Rose shortly after the crash, with comments by veteran Concorde pilot John Hutchinson, said they could no doubt have “got away” with being overweight had other things not gone wrong. The crew had decided 150 knots should be V1, the speed at which they would be committed to continuing the takeoff, and 183 knots should be VR, the speed at which they would rotate and expect to soar into the sky.

A supersonic delta-wing aircraft like Concorde differs from other aircraft in that the wings do not provide any real lift before rotation. In consequence, the tires continue to bear the entire weight of the aircraft throughout the takeoff run. This in turn means they are particularly vulnerable just before rotation, as there is not only the weight of the aircraft to consider but also the tremendous centrifugal forces acting on their treads due to the wheels’ high rate of rotation. In addition, at high speeds sharp objects on the runway are far more likely to cut into them.

Shortly after Concorde had reached V1, the right-hand tire on the left-hand main landing gear ran over a curved strip of metal that had just fallen off a DC 10 that had taken off shortly before. Curved like a loop, the titanium strip was lying sideways up, with its concave side facing the oncoming tire, thus ensuring the tire would trap it rather than roll it over and bend it flat. The tough metal sliced into the tire, causing the tire to break up under the enormous centrifugal forces. Later, investigators found a 10 lb (4.5 kg) piece of rubber from the tire on the runway near that point.

After complex studies the BEA investigators concluded the lump of rubber had forcefully struck the underside of the wing, pushing it and the fuel tank so rapidly inward that it induced a shock wave in the fuel of such intensity that, with the tank virtually full and no air-filled spaces to absorb the shock, the tank ruptured elsewhere, a phenomenon that had never been seen before in a passenger aircraft. Had the piece of rubber just pierced the tank, as in a previous instance in Washington in 1979, the damage to the tank would doubtless have been less.

From the amount of fuel on the runway and other evidence, it is estimated that kerosene was pouring out from under the wing at a rate of sixty kilos a second. In the Washington incident mentioned above, the fuel did not catch fire, and the aircraft was able to take off and return safely. Perhaps because of the much greater amount of fuel, and very likely because a damaged wire in the landing gear was producing sparks, the leaking fuel then caught fire.