An airport worker said that in late August the aircraft was heading for the runway to take off when a fire developed in one of the starboard wing engines, which both failed and fell off just before Sunday's crash. The fire was put out on the ground automatically by the plane's extinguishers.
Boeing yesterday issued a bulletin instructing airlines to check the four-inch-long fuse pins after a December 1991 crash of a China Airlines cargo 747-200F at Taipei.
The four steel pins for each engine link the support struts to the wings and are designed to break in the event of the wing structure being threatened by unstable engine movements or during a crash landing. In both the China Airlines crash and Sunday night's accident to an identical aircraft the two starboard-side engines fell off.
Notice that the service bulletin was to be issued had been given to airlines early last month and Boeing held two meetings with groups of operators at its Seattle headquarters later in September to discuss its implications. Airlines emphasised yesterday that this kind of delay is not unusual because the bulletin was not considered to be urgent, but clearly it will raise questions over whether the disaster could have been averted. El Al was unable to say last night whether the pins on the crashed plane had been inspected.
The bulletin is to be endorsed by the US Federal Aviation Authority this week. It applies to three versions of the 747, the 747-100, 747-200 and 747-300 fitted with Pratt & Whitney or Rolls-Royce engines. Both crashed aircraft had Pratt & Whitney JT9D engines.
One operator said the pins had been redesigned a number of times in recent years to try to improve them. Boeing admitted yesterday that it had received 15 reports over the past seven years of microscopic cracks in the pins, but emphasised that the pins could not be blamed for either crash.
In December 1979, the No 4 starboard-side engine on a Pan Am cargo 747 nearly sheared off, causing a severe fire, during a landing at Heathrow. The accident was attributed to metal fatigue and weakness as a result of a collision with a luggage loader at Chicago three years before.
The bulletin issued yesterday requires operators to check the pins after 5,000 flights and every 1,000 thereafter. British Airways said yesterday that it had checked the pins visually as soon as it knew the warning was imminent and it is replacing all pins which have been in use for more than 5,000 flights, even though its aircraft are fitted with a different type of engine.
One airline source criticised Boeing's move, saying it was a panic measure designed to focus attention on one possible cause when 'it was much too early to focus narrowly on the tiny components. You have to look at the whole sequence of events and it wasn't these pins which began the engine fires.'
Dutch officials yesterday denied claims that they had accused the El Al pilot of having caused the disaster by trying to land on the wrong runway. Recorded conversations with the airport control tower showed that the pilot, Isaac Fuchs, overrode advice from the tower to land on the airport's runway 06, choosing instead to land on runway 27.
A spokesman from the Dutch Transport Ministry insisted the government was not trying to discredit the pilot by publishing details of the disagreement: 'We don't blame him at all, but unless we find the flight recorder, we'll never know exactly why he chose that runway.'