How cracks in jet engines elude exams, with deadly results

As regulators around the world order urgent inspections of certain Boeing 777 engines after one failed dramatically over suburban Denver last Saturday, they must also wrestle with a decades-old quandary: The complex technology necessary to find cracks buried within metal parts can produce notoriously inconsistent results. Not only are the tests prone to vague readings, but the results are only as good as the training and attention span of the human examiner. Indeed, after a 2018 failure of an engine fan blade identical to the one involved in the Denver episode, investigators found inspections had twice missed a crack that began years earlier. “It probably was there and they just didn’t find it,” James Wildey, a retired NTSB metallurgical expert, said of the internal imperfections that led to the most recent failure. “The indications are the crack should have or could have been detected.” <br/>