Air France Flight 4590 - Previous Tyre Incidents

Previous Tyre Incidents

In November 1981, the American NTSB sent a letter of concern, which included safety recommendations for Concorde, to the French BEA. This communiqué was the result of the NTSB's investigations of four Air France Concorde incidents, during a 20 month period, from July 1979, through February 1981. The NTSB described those incidents as "potentially catastrophic," because they were caused by blown tyres during takeoff. The NTSB also expressed concern about the lack of adequate remedies, on the part of the French, as well as improper crew responses to those incidents.

• 13 June 1979: The number 5 and 6 tyres blew out during a takeoff from Washington, D.C. Dulles Airport. Fragments thrown from the tyres and rims damaged number 2 engine, punctured three fuel tanks, severed several hydraulic lines and electrical wires, in addition to tearing a large hole on the top of the wing, over the wheel well area.

• 21 July 1979: Another blown tyre incident, during take-off from Dulles Airport. After that second incident the "French director general of civil aviation issued an air worthiness directive and Air France issued a Technical Information Update, each calling for revised procedures. These included required inspection of each wheel and tyre for condition, pressure and temperature prior to each take-off. In addition, crews were advised that landing gear should not be raised when a wheel/tyre problem is suspected."

• October 1979: Tyres number 7 and 8 failed during a takeoff from New York's JFK Airport. In spite of the well-publicized danger from the previous incidents, the crew ignored the new safety recommendations and raised the landing gear and continued to Paris. There was no subsequent investigation by the French BEA or the NTSB of that incident.

• February 1981: While en route from Mexico City to Paris, Air France (F-BTSD) blew more tyres during another takeoff at Dulles Airport. Once again, the crew disregarded the new procedures by raising the landing gear. The blown tyres caused engine damage which forced the flight to land at New York JFK Airport. The NTSB's investigation found that there had been no preparation of the passengers for a possible emergency landing and evacuation. The CVR was also found to have been inoperative for several flights, including one which followed a layover in Paris.

To save on weight, Concorde was designed to take off without the assistance of flaps or slats. That required a significantly higher air and tyre speed, during the takeoff roll, which imposed a much greater centripetal force load on the tyres. That higher speed increased the risk of tyre explosion during takeoff. When the tyres did explode, much greater kinetic energy was carried by the resulting fragments travelling at great speeds tangentially from the rims (the kinetic energy of an object being directly proportional to the square of its speed), increasing the risk of serious damage to the aircraft. A thicker skin on the bottom side of the wings could have prevented serious damage from an exploding tyre, but that would have added too much weight, canceling out most of the advantage of not having flaps or slats.