The airborne failure of a jet engine that spewed a trail of metal over a Colorado city is putting regulatory focus on the design and strength of engine covers. Four minutes after the United Airlines UAL flight to Honolulu, + 1.83% from Denver on Saturday, pilots and passengers heard a loud bang, and the plane’s right engine began to vibrate, according to preliminary analysis by the National Board of Safety in the Transportation of the cockpit voice recorder. . In 20 minutes, the Boeing BA, -0.36% 777 had landed on the runway back to Denver International Airport, with no one injured on the ground or aboard the plane. However, large chunks of debris fell from the sky, landing on courtyards and a soccer field. Photos and videos taken by passengers show the plane’s right engine, stripped of its front covers, oscillating and on fire.
Researchers have focused on a fan blade that had weakened over time and broke at its base. That rapidly rotating blade remnant appears to have cut a second blade roughly in half. But researchers are still trying to understand why the engine’s front outer cover, known as the fairing, was later ripped off, according to NTSB President Robert Sumwalt. Something similar happened in a handful of other motor failures caused by broken fan blades in recent years. “We certainly don’t expect the hood to come apart like this,” Sumwalt said this week, during a briefing with reporters. He added that safety board investigators would examine the engine’s inspection and maintenance records. Such damage to the outer sections of the engine is not supposed to occur under current inspection and manufacturing systems, which have ushered in an era of record-breaking airline safety in the U.S. The incident raises concerns about whether the engine covers they’re too vulnerable to damage from high-speed forward-flying engine components, plus questions about why the fan blades broke, some safety experts said. An expanded version of this report appears on WSJ.com. Also popular on WSJ.com: COVID-19 Vaccine – What You Need to Know When You Get the Shot. Stimulus Package: What’s in Joe Biden‘s ‘American Bailout Plan’?