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'Cracks in aeroplanes are really quite common'
David Learmount
 real 28k

Tuesday, 25 July, 2000, 15:43 GMT 16:43 UK
Q&A: Cracks in Concorde
concorde
Concorde ages more slowly than other passenger planes
David Learmount, Operations and Safety Editor of Flight International Magazine, answered our questions about Concorde safety, following the discovery of cracks in the wings of all seven of British Airways' Concorde supersonic jets. The interview was conducted before the crash of the Air France Concorde.

Is it normal for cracks to appear in planes?

Cracks in aeroplanes are really quite common, especially as the aeroplanes get a little bit older.

How big are these cracks?

It's important to understand that we're talking about really tiny cracks here and in most cases, cracks that couldn't even be seen by the human eye.

Should air passengers be concerned about these cracks?

Passengers have a perfect right to be concerned if airlines don't take cracks seriously, but on the whole they do.

When do the tiny cracks become a problem?

When a crack develops, you assess whether the aircraft has to be grounded. If the safety engineers decide it can still safely fly, then they have to assess how quickly the crack has to be fixed because ultimately if it's not fixed it will propagate. But of course airlines frankly wouldn't be inclined to take a risk like that and b, wouldn't be allowed to take a risk like that.

So what are airlines doing about the cracks?

Their engineers use various systems to detect these cracks, in this particular case the cracks were detected by what is known as an ultra-sound check, which is really like taking an x-ray of the metal. Aeroplanes of all types, not just Concorde, are subjected to these checks on a regular basis.

In this particular case British Airways asked the manufacturer of this particular part, the French company Aerospatiale, to have a look at the cracks. Aerospatiale and also the UK civil aviation authority safety people said the cracks were fine as they were, but to watch in case any of them got any bigger. Now, the crack on one of the seven Concords, has started to get bigger, this was about a week ago and BA immediately grounded the aeroplane and brought the engineers in again, who have been working out a fix, which British Airways hopes to have in place by September.

These cracks all appeared in the same place, does that mean there's a design fault with Concorde?

In this particular case yes, there might actually have been a design fault, but as soon as you put the words aeroplane and design fault in the same sentence everybody panics. We're talking about a really, really minor design fault. This is a very small crack in a very small part of a very complex milled metal construction, a construction that is far stronger than it needs to be.

So is Concorde just getting too old?

Concorde is getting quite old, but it's not worked very hard, Concorde has a very easy life. It works about a quarter the number of trips or flying hours of any other jet in the sky and that means it spends a disproportionate amount of time in the hangar being given a disproportionate amount of love by the engineers. It is actually ageing very, very slowly. It's quite possible that BA will be able to fly this aeroplane much much longer than it could normally fly another ordinary jet because the ordinary jets work much harder.

So these cracks aren't specific to supersonic aircraft?

No. Cracks in metal occur because of metal fatigue. It's rather like if you were to take a piece of metal wire and you were to keep bending and bending it, it will eventually break. These cracks are definitely not specific to supersonic aircraft and are found in aeroplanes of all types, jumbos, airbus, 747's. The engineers crawl all over the aircraft looking for these faults on fairly regular basis, and that goes for every aircraft flying today.

How regular and thorough are these checks?

The schedule of checks gets more and more frequent as the aircraft ages and it's not the same for every aeroplane and it's not the same for every part of every aeroplane. But the most important factor is not an aeroplane's age, but the number of flights it has actually flown and Concorde flies very, very few flights. The way the checking schedule is determined is that every aeroplane, including Concorde, before it's flown, is set up in a hangar to have the most amazing stresses inflicted on it to replicate really rough flights, and that goes on 24 hours a day, for years and years until the aeroplane eventually breaks. This is literally replicating the lifetime behaviour of an aeroplane so they actually know in advance of the aeroplane reaching any given age, what kind of structural weaknesses will start to appear and where to look for them.

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