Investigators in the Concorde accident undertook research to find incidents that involved tyres or landing gear on the Concorde since its entry into service. Archives from EADS, Air France, British Airways, BEA, AAIB, DGAC, CAA and Dunlop were consulted to establish a list of such incidents.
The assembled list contained fifty-seven entries; all cases of tyre bursts or deflations. Thirty cases were for the Air France fleet and twenty-seven for British Airways.
Of these events;
•Twelve had had structural consequences on the wings and/or the fuel tank •Six led to penetration of the tanks
•Nineteen of the tyre bursts or deflations were caused by foreign objects •Twenty-two occurred during takeoff
•One case of tank penetration by a piece of burst tyre
However none of the events showed any rupture of a tank, a fire, or a significant simultaneous loss of power on two engines.
It was clear that the case of tyre bursts or deflation was not a new topic as far as the history of Concorde is concerned. In this accident and in many other incidents, this material (rubber and other materials constituting the tyres) failure led to other failures on the aircraft structure. Understanding the destruction mechanisms of the tyres and tank rupture as well as the production of the fire would arm the investigators with powerful tools in preventing future accidents.
Tests were carried out by Air France’s tyre supplier, Goodyear, at their technical centre in the United States to reproduce the conditions on the day of the accident. Two new Concorde tyres were used for the test and curved metallic strips with comparable dimensions to the one found on the runway were also used.
The tyres were installed on the side of a trolley towed by a truck. The load spread out on the trolley allowed each tyre to bear a load of about twenty-five tons, equivalent to that on each main landing gear tyre on Concorde. Taking into account the test equipment and the load, the speed of the truck was around 10 km/h. The sample strips were stood on edge on a concrete surface.
During the tests:
•An initial positioning of the strip, done with a titanium strip, resulted in its being flattened by the tyre. •In a second position, the strip remained stable on its cutting side and the tyre was cut into, •The tyre cut went right through its thickness, practically all across the width of the area in contact with the ground and in accordance with the shape of the strip, •This cut continued as tearing onto the tyre shoulders and sidewalls through a static rupture in the direction of the reinforcing material of the tyre body, •The static tear spread as far as the tyre beads, in other words slightly more deeply than the tear noted on the remains of burst tyre in the accident.
Tyre test truck
Metallic strip under the tyre
Theoretical Study of Metallic Strip Cutting Tyre
In the course of the investigation, the Mechanical Industries Technical Centre (CETIM), which is specialised in the study of polymers, plastics and composites, was asked to determine the theoretical behaviour of a tyre running over an obstacle like a metallic strip standing on edge. In order to do this, the CETIM conducted a study using finite element modelling on a bias ply carcass tyre with characteristics similar to those fitted on the ill-fated F-BTSC.
The mechanical and chemical characteristics of the materials were supplied by Goodyear, the manufacturer. Those of the metallic strip corresponded to the characteristics of the one found on the runway.
Two cases were considered:
•A so-called “short” strip of which at least one end is inside the contact area between the tyre and the ground.
•A strip that was long enough to protrude beyond the contact area.
This theoretical study shows that at the ends of the strip, the damage caused was typified in both cases by separation...