Black box holds clue to air tragedy

As the Queen and Prime Minister Gordon Brown expressed their sadness at "the dreadful loss of life", air crash investigators were trying to work out what happened to the Spanair MD-82 while taking off from Madrid airport for the Canary Islands.

Experts pointed to the rarity of take-off accidents and to the fact that Europe has been free of major plane disasters in recent years. Take-offs and landings are seen as the critical times for planes and their cockpit crews.

Kieran Daly, editor of internet news service Air Transport Intelligence, said: "Take-off accidents are very, very rare. You reach a point in take-off when it is unlikely that anything can go wrong but if things do go wrong, they can go wrong very quickly.

"On take-off, pilots reach a point of no return, known as V1 speed, which is usually reached about two seconds before take-off.

"If you go above V1 and abort the take-off, there is insufficient room at the end of the runway and there is the chance of going off the end of the runway at a very fast speed and things can then go very badly wrong."

Mr Daly said the recovery of the flight data recorder - actually orange in colour but popularly known as the black box - would allow investigators to know the state of the engines in the seconds before the crash. "They should be able to work out whether the plane was in a flyable condition in those last few moments," Mr Daly said.

Meanwhile, Dr Guy Gratton of the school of engineering and design at Brunel University in west London, said automatic thrust reverser deployment will be one of the things that air crash investigators will be looking at.

It is thought that the thrust reversers, normally only used just as a plane touches down, were deployed on the Spanair MD-82 that burst into flames at Madrid airport with the loss of more than 150 lives.

In May 1991, a Lauda Air Boeing 767 crashed in Thailand with the loss of 223 lives when the thrust reverser automatically went into operation.