Broken fan blades have led to fatal accidents in the past. In 1989, a Boeing 737 crashed near Kegworth, England, killing 47 people after a fan blade on an engine manufactured by CFM International broke and pilots accidentally shut off fuel for the other engine.
In February 2018, an engine fan blade broke during a United flight over the Pacific, resulting in engine damage and a loss of the hood. Like the flight last weekend, this aircraft was a Boeing 777 that was equipped with a PW4077 engine. The pilots were able to land the aircraft safely in Hawaii without injuring the 374 passengers and crew on board.
After the NTSB investigated that episode, it blamed Pratt & Whitney, saying that one of its inspectors lacked the necessary training to identify signs of a faulty blade, resulting in “a cracked blade being put back into service became where it finally broke ”. In 2019, the FAA ordered further inspections of the fan blades in these motors. More recently, the agency has inspected the fan blade fragment of the Japanese flight and considered whether the inspections of the component should be adjusted, it said on Monday.
When airlines buy new aircraft, they usually have a choice of which engine to use. In some cases, they can even lease engines from a bank, according to Eric Jones, chairman of the aeronautical maintenance science department at Embry-Riddle Aeronautical University.
“They’re very interchangeable,” said Mr. Jones.
United became the first customer of the Boeing 777 in the 1990s and equipped the jet with the new PW4000 engine from Pratt & Whitney. All of Nippon Airways, another early customer, also chose this engine.
Once a major airline takes ownership of an aircraft, it typically takes responsibility for the routine maintenance and inspection of all parts of the aircraft. Pilots orbit aircraft before each flight and perform visual inspections, including the fan blades. Technicians conduct checks on various systems. Often times, when a part such as an engine needs a more thorough repair or inspection, it is sent to a third party or the manufacturer for inspection.