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Friday, 1 September, 2000, 14:46 GMT 15:46 UK
Q&A: Concorde crash
The French Air Accident Investigation Bureau report published at the end of August contained little new information about the Concorde crash and did not pinpoint its cause. David Learmount, operations and safety editor at the aviation magazine Flight International, answers the crucial questions.

How do the pilots come out of the report?

The whole crew, pilots and flight engineer, performed in an exemplary and professional manner. They made no mistakes, and performed the drills appropriate to the information they had exactly as they had been drilled to do in training, and all without panic. When the aircraft crashed it was because it had become uncontrollable, and there was nothing that the crew could have done to prevent that situation arising. This is an accident in which the well-worn verdict "pilot error" will play no part whatsoever.

Do we know any more about the runway debris which caused the tyre blow-out?

There is unmistakable evidence of a "significant gash" in the tyre which burst, but although the investigators believe they have found a piece of metal on the runway which might have caused it to burst, they are not yet certain of this. Little is known about the strip of metal except that it did not come from the Concorde itself. It may not even have been an aircraft part, but possibly even have come from an airport vehicle of some kind.

Why is Concorde so vulnerable to a tyre burst - compared with other passenger jets?

Concorde's tyres are at a much higher pressure than ordinary aircraft tyres, and its take-off and landing speeds are also higher.

Concorde's tyres are not, in themselves, the problem, it is what they are asked to do which is the problem.

What steps are taken to detect debris on runways, and are they enough?

There are no rules about runway checks, but most airports check runways for debris at least once a day and immediately remove any debris reported by pilots during their take-off or landing runs.

Does the report make it more or less likely that Concorde will fly again?

If this report makes any difference at all to the likelihood of Concorde flying commercially again, it reduces the chances by confirming earlier findings and suspicions. The report's recommendations state that, before Concorde can fly again, modifications must "guarantee a satisfactory level of safety as regards the risk of tyre blow-outs". If the words are to be taken literally, they mean that Concorde must, in the future, be able to survive the worst tyre bursts which could be conceived as possible, not simply that tyre bursts themselves must be made less likely.

What modifications are being considered on Concorde, and could they prove too costly?

The problem that the airlines face is that they alone must shoulder the costs of any such modification. Since the aircraft is no longer in production, there is no incentive for the manufacturers to invest in improving the product. Since Concorde is three quarters of the way through its service life and generates prestige rather than high profits for the airlines, the cost-benefit mathematics do not look good for a return to service.

Possible modification options are to protect the underwing area from tyre bursts by strengthening it, or to modify the tyres and undercarriage so that any burst would cause less severe damage. This may sound easy but is not. That is why it has not been done successfully before despite seven events involving highly damaging tyre bursts and more than 60 involving lesser damage. Fixes have been applied, but the accident proves that they are not infallible and more has to be done.

What investigations are still to be completed by the French authorities?

This preliminary report is a new sign of greater openness in the aviation accident investigation process. Previously the world would have had to wait for the full report which will probably take another year and possibly 18 months. There is a huge amount yet to be established, not least precisely what caused the underwing fuel leak to ignite, exactly what damage caused the two left engines to fail, and what damage was done to other aircraft systems, like hydraulic, electrical and fuel lines.

How do investigators work out the sequence of events that lead to a crash from thousands of pieces of debris?

It's not just working with debris that investigators do, however important that is. They also have information from air traffic control and radar tapes, witnesses (some of them, like controllers and pilots, expert witnesses), the cockpit voice recorder and the flight data recorder.

But with the debris metallurgists can distinguish between parts which were damaged in the tyre burst and airborne fire and those which were damaged by the crash and subsequent fire. The main scientific and engineering expertise applied is metallurgy and forensic chemistry, as well as previous experience in the field.

What does the French accident investigator's preliminary report reveal that we did not know?

The preliminary report has done little to add to what was stated on 16 August, when Concorde's certificates of airworthiness were withdrawn, grounding the entire fleet.

It was stated that the reason for grounding was that a tyre burst alone had been enough to bring the aircraft down, and that was considered unacceptable because tyre bursts are "not an improbable event on Concorde". This statement has been reinforced by study carried out since then. Other new material, like the communications between the pilots and with air traffic control, have simply fleshed out what was already know in lesser detail, without changing any established facts or theories.

The Concorde Crash

Return to the skies?

The investigation

The crash





See also:

18 Aug 00 | Europe
16 Aug 00 | Business
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