But a dispute appeared to be breaking out between the Dutch and US aviation authorities when the Americans said last night that no action would be taken on the Dutch report until Monday at the earliest.
Yesterday, Henk Wolleswinkel, head of the Dutch aviation inspectorate, said metal fatigue in the strut that holds the engine to the wing seemed the most likely cause of the crash. This follows the recovery on Thursday of the number three engine from a lake, near where the number four engine was found. Both were discovered to be in relatively good condition.
Mr Wolleswinkel said that the absence of an explosion or heavy internal damage to the Israeli jet's engines indicated that it was the engine supports that were at fault rather than the engines themselves.
'We have no proof, but no reason to believe this hypothesis is not valid. There is some shortcoming in the way the engine is suspended, some form of metal fatigue,' he told a news conference at Schiphol Airport. Such metal fatigue was previously unknown to occur in this sort of craft. 'For people familiar with metal fatigue it is shocking to be confronted with data so similar,' he said. He added that passenger aircraft were unlikely to be affected because they are not loaded as heavily as cargo planes, which also have more powerful engines. A pilot recently told the Independent that cargo planes were 'always filled up to the gunwales' and accurate checks of their payloads were not made.
There are about 80 cargo planes around the world with the same Pratt and Whitney engines as the El Al aircraft, which crashed into an Amsterdam suburban housing estate, killing an estimated 70 people on the night of 4 October. It was the remarkable similarities between the accident involving the El Al plane and a crash involving a China Airlines freighter in December 1991 that led the Dutch investigators to issue their preliminary findings so quickly.
Both planes were 747-200Fs with Pratt and Whitney JT9D engines, and both crashed shortly after take-off carrying maximum loads of around 250,000lb. The aircraft both had around 45,800 hours' flying time and had made between 9,000 and 10,100 flights.
The Amsterdam disaster began when the El Al pilot reported fire in the number three engine shortly after taking off from Schiphol en route to Tel Aviv, but there is no clear evidence that there actually was a fire. Both right-hand engines tore off the craft as the pilot attempted to return to the airport, but the jet crashed into the Bijlmermeer estate outside Amsterdam after 14 minutes in the air.
Mr Wolleswinkel has alerted the US Federal Aviation Administration, expressing doubts about the airworthiness of the craft if they have made more than 6,000 flights, but he has not asked the US authorities to ground the planes. A spokesman for the Dutch authorities last night said that he hoped checks would be instituted immediately.
However, a spokesman for the FAA said last night that 'no action was being taken now but an answer to the letter from the Dutch authorities would be sent on Monday. We are continuing to look into this in conjunction with the manufacturers.'
Soon after the crash, Boeing asked carriers to check the fuse pin at the junction of the wing and strut. The pin is designed to snap to allow an engine that is vibrating irregularly to break cleanly from the aircraft rather than remaining to cause damage to the wing.
Mr Wolleswinkel said that data recovered from the flight recorder supports the metal-fatigue theory, although the recorder's tape was barely readable for the period after the engines fell off. The cockpit voice recorder has still not been recovered.
Boeing said last night that 'it is too early for any conclusions to be made'.Reuse content