Air safety officials are focusing on engine fan blades in their investigation of what caused a massive engine failure aboard a Boeing 777-222 commercial airliner Saturday, strewing huge aircraft parts across neighborhoods in suburban Denver.
This engine failure may be related to several others stretching back for years, but first let's review the details of the most recent event.
United Airlines Flight 328, bound for Honolulu, reported right engine failure shortly after leaving Denver International Airport at 12:49 p.m. The engine caught fire and began to disintegrate as passengers recorded and photographed the failing engine in flight.
Chad Schnell was among the passengers with a front row view of the damaged and burning engine. This is what he saw outside the window:
Some of the missing engine pieces ended up in someone's front lawn in Broomfield, Colorado.
Here is a scale comparison to put that in perspective:
The aircraft, with 231 passengers and 10 crew, returned to Denver and landed safely shortly after takeoff. Fortunately, no one was injured.
Who makes the engines for the Boeing 777?
For United Airlines Flight 328 it was Pratt & Whitney, a subsidiary of defense contractor Raytheon. According to their parent company, "Pratt & Whitney designs, manufactures and services the world’s most advanced aircraft engines and auxiliary power systems for commercial, military and business aircraft."
The Federal Aviation Administration has ordered increased fan blade checks on Pratt & Whitney PW4077 engines, the type used by United 777s. Commercial airlines around the world grounded their 777s, pending investigation. Boeing has recommended the suspension of operations of the 69 in-service and 59 in-storage 777s using Pratt and Whitney 4000-112 engine until further notice.
United has 44 other Boeing 777s, all with GE engines, which are not affected by United's 777 grounding or the FAA directive. The airline will use one of those planes, for example, to fly between San Francisco and Taipei, Taiwan, in March instead of one of its grounded 777s, according to United spokesman Charlie Hobart.
American Airlines has 67 Boeing 777s in its fleet. They are powered by Rolls-Royce and GE engines, which also aren't affected by the FAA's directive. The planes were used for international flying before the pandemic and are now frequently used for flights within the USA, spokesman Sarah Jantz said.
Has this happened before?
Another incident involving a Boeing plane running Pratt & Whitney engines also dropped engine parts after a separate mid-air explosion over the Netherlands on the very same day.
The Dutch incident involved a Boeing 747 cargo plane powered by Pratt & Whitney PW4000 engines, a smaller version of those in the United Airlines Boeing 777 involved in the Denver incident, according to Reuters. Longtail Aviation flight 5504, a cargo plane, scattered small metal parts over Meerssen, causing damage and injuring a woman shortly after take-off on Saturday.
The troubled United flight is reminiscent of one from February 2018, in which a United Boeing 777 from San Francisco lost its engine cover and began to shake about an hour from Honolulu. The plane was able to land safely, but passengers were terrified. Investigators said a broken fan blade caused the failure.
That 777 also had Pratt & Whitney 4000 series engines, similar to the ones that failed in in Saturday's flights.
The NTSB report said the failure in 2018 was caused by a fan blade that broke off and damaged the engine. The board cited inadequate inspections of fan blades and said inspectors were not properly trained.
Inspections of the fan blade that failed had shown evidence of weakening titanium in 2010 and 2015, but an inspector attributed them to the way they were painted, the NTSB concluded. Bloomberg reported that the engine was a Pratt & Whitney PW4077. The NTSB concluded that Raytheon Technologies Corp.’s Pratt & Whitney division didn’t create adequate test standards.
In December, two fan blades broke off in flight on a Japan Airlines 777-200 with a Pratt & Whitney 4000-112 engine on a flight from Naha to Tokyo, as reported by The Seattle Times.
The Associated Press reported the FAA wants more frequent inspections of the hollow fan blades used in Pratt & Whitney 4077 jet engines on United planes.
The National Transportation Safety Board said two of the 777's fan blades were fractured, other blades were damaged and part of one was embedded in the engine's containment ring – metal or composite material designed to keep broken blades inside the engine, according to Aerospace America.
The NTSB's initial examination found:
- The inlet and cowling were separated from the engine.
- Two fan blades were fractured.
- One fan blade was fractured near the root.
- An adjacent fan blade was fractured about mid-span.
- A portion of one blade was embedded in the containment ring.
- The remainder of the fan blades showed damage on the tips and leading edges.
The NTSB said it was too early to draw conclusions on what caused the engine to fail. Most of the damage was confined to the engine, and the aircraft sustained minor damage.
The investigation is ongoing. The cockpit voice recorder and flight data recorder are in Washington, where the NTSB will analyze the data.
The 777 series is a two-engine American wide-body commercial airliner manufactured by Boeing Commercial Airplanes. It's the world's largest twin-jet and began flying in 1994. It was officially introduced in 1995.
United is the only U.S. airline with the Pratt & Whitney PW4000 in its fleet, the FAA said. United says it has 24 of the 777s in service.
The United 777 aircraft in Saturday's incident is 26 years old.
Read more:
What travelers need to know: United Airlines engine failure on Boeing 777 flight from Colorado
SOURCE USA TODAY Network reporting and research; National Transportation Safety Board; Federal Aviation Administration; Associated Press; Aviation Week; Aerospace America; flightglobal.com; skybrary.com
Dawn Gilbertson, Javier Zarracina, Karina Zaiets, Jon Briggs, Steve Kiggins, and Shawn Sullivan contributed to this report.
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