Inquiry centres on Concorde 'thin skin'

Experts investigating last week's Concorde crash near Paris, in which 114 people died, are concentrating their attentions on the tyres used. They have effectively concluded that both Rolls-Royce and the Air France maintenance staff are in the clear.

Experts investigating last week's Concorde crash near Paris, in which 114 people died, are concentrating their attentions on the tyres used. They have effectively concluded that both Rolls-Royce and the Air France maintenance staff are in the clear.

They will focus on the effect on the aircraft's structure when a tyre punctures at speed and the wheel housing disintegrates. It is now almost certain that the catastrophic chain of events which destroyed flight AF4590 began with either one or two burst tyres in the four- wheel landing-gear under the left wing. Burst tyres on aircraft are rare but not unheard of. There have been two previous incidents involving punctures on Concordes, one on take-off and one on landing, in the past 21 years.

What is unusual - and now the focus of attention of the two teams of investigators - is the mortal damage which the burst tyres (manufactured by Goodyear) caused to the Concorde within seconds of the start of its take-off run at Charles de Gaulle airport last Tuesday afternoon.

The French government has ordered Air France to suspend all Concorde flights until the safety implications are studied and addressed. The six operational British Airways Concordes continue to fly. They use tyres from Dunlop Aviation.

French police appealed yesterday for eye-witnesses of the crash to come forward to help the two investigation teams - a team of experts and a team of judges and gendarmes - to establish the precise sequence of events which led to the crash. Anyone who saw the aircraft take off, or watched any part of its one-minute flight to disaster, is asked to call 0033(0) 148963028.

The international team of air-accident investigators, French, British, American and German, are now convinced that the fire on the left side of the aircraft did not start in the engines. The speculation that last-minute repairs to one of the four Rolls-Royce engines may have caused the crash, is now thought to have been misplaced.

None of the debris that was found on the runway or along the two-mile flight path of AF4590 came from within the engines. It was the complete failure of one engine and the partial failure of another which brought the aircraft down, but the engines seem to have been intact until the plane crashed.

Officially, the cause of the engine failure, and spectacular fire shown in amateur photographs of the doomed plane, has not been established.

Independent aviation experts say that the likelihood is that splinters of metal, either from the wheels of the aircraft or the iron strips reinforcing the burst tyres, pierced the underside of the left wing and holed the fuel tanks or fuel lines. Under this theory, the engines failed because they were starved of fuel.

"It should be remembered that the fuselage and the wings of Concorde are made from comparatively thin struts and sheets of aluminium," one expert said yesterday. "At the speed the plane was travelling (over 200 miles an hour on its take-off run), it is entirely possible that a projectile (from the tyre-stripped wheels) could pierce the fuel reservoir."

This has happened before. On 15 June 1979, an Air France Concorde burst two tyres on take-off from Dulles International Airport near Washington, DC. A wing fuel-tank and hydraulic control-lines were damaged by flying debris but there was no fire and the aircraft made a safe emergency landing 20 minutes later.

The two investigation teams, who are co-operating rather uneasily, have different briefs. The three investigating judges, assisted by gendarmes, are trying to established whether there are grounds for a criminal prosecution for manslaughter. The accident investigators are trying to establish whether the Concorde disaster - after 25 years of safe, commercial flying - has exposed a structural weakness in the design of the aircraft.

British Airways said last night that it had no plans to follow Air France's lead and suspend flights on Concorde until the cause of the crash was identified. BA's fleet of Concordes has experienced 12 blow-outs since 1979 and the company has installed a safety system in the cockpit whereby an alarm will ring and a light flash in the event of a tyre bursting on take-off.