The long fan blades are made of titanium, the hardest metal available. The funnel-like blades let as much air as possible — as efficiently as possible — into the turbine, where it gets heated up, creating propulsion.
In some engine types, the fan blades are hollow inside with a view to saving weight. The tips of the fan blades, usually between 22 and 38 per engine depending on the class of aircraft, rotate with supersonic speeds inside the inlets. Especially on takeoff, such huge high-tech propulsion devices for wide-body aircraft run at full throttle to lift off aircraft weights of 250 tons or more.
It was during this most critical phase of the flight that two incidents happened on Saturday, one in Europe and the other in the United States.
Initially, a 30-year-old Boeing 747-400 freighter took off from Maastricht in the Netherlands for a flight to New York. It had just become airborne when an explosion occurred on the outer left engine. Broken blades from one of the compressors flew out of the back, slightly injuring an elderly woman and a child on the ground. Worse things could easily have happened as the sharp-edged metal pieces punctured parked cars in the suburb of Meerssen like knives coming down from the sky.
The crew declared an emergency. The plane went into a holding pattern, then dumped fuel before bringing down the crippled Jumbo to a safe emergency landing an hour later in nearby Belgian Liege. The Dutch Safety Board (DSB) initiated an investigation into the cause and circumstances of the incident.