Aviation safety officials are focusing on the engine fan blades in their investigation into the causes of a massive engine failure aboard a Boeing 777-222 commercial airliner on Saturday, spilling huge parts of plane in suburban neighborhoods of Denver.
This engine failure can be linked to several others dating back years, but let’s take a look at the details of the most recent event first.
United Airlines Flight 328, to Honolulu, reported a failure of the right engine shortly after leaving Denver International Airport at 12:49 p.m. The engine caught fire and began to decay as the passengers recorded and photographed the failed engine in flight.
Chad Schnell was among the passengers with a front row view of the damaged and burning engine. Here’s what he saw outside the window:
Some of the missing engine parts ended up on someone’s lawn in Broomfield, Colorado.
Here’s a scale comparison to put that in perspective:
The plane, with 231 passengers and 10 crew members, returned to Denver and landed safely shortly after takeoff. Fortunately, no one got hurt.
Who manufactures 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 the Pratt & Whitney PW4077 engines, the type used by the United 777s. Commercial airlines around the world have grounded their 777s, pending an investigation. Boeing has recommended the suspension of operations of the 69,777 in service and the 59,777 in storage using the Pratt and Whitney 4000-112 engines until further notice.
United owns 44 other Boeing 777s, all powered by GE engines, that 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 777s on the ground, 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 are also not affected by the FAA directive. The planes were used for international flights before the pandemic and are now frequently used for flights within the United States, spokeswoman Sarah Jantz said.
Has this ever happened?
Another incident involving a Boeing plane running on Pratt & Whitney engines also dropped engine parts after another explosion in flight over the Netherlands on the same day.
The Dutch incident involved a Boeing 747 cargo plane powered by Pratt & Whitney PW4000 engines, a smaller version of those of 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 takeoff on Saturday.
United’s disrupted flight is reminiscent of 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 the passengers were terrified. Investigators said a broken fan blade was the cause of the failure.
This 777 also had Pratt & Whitney 4000 series engines, similar to those that failed on Saturday flights.
The NTSB report says the 2018 failure was caused by a fan blade that broke and damaged the engine. The council cited inadequate inspections of the fan blades and said the inspectors were not properly trained.
Failed fan blade inspections showed signs of titanium weakening 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 the Pratt & Whitney division of Raytheon Technologies Corp. did not create adequate testing standards.
In December, two fan blades failed in flight on a Japan Airlines 777-200 equipped with a Pratt & Whitney 4000-112 engine during a Naha flight in Tokyo, as reported by the Seattle Times.
The Associated Press reported that the FAA wanted more frequent inspections of hollow fan blades used in Pratt & Whitney 4077 engines on United planes.
The National Transportation Safety Board said two of the 777’s fan blades were fractured, other blades damaged, and part of one was embedded in the engine’s containment ring – either metal or a composite material designed to hold the broken blades inside the engine, according to Aerospace America.
The initial review of the NTSB found:
- The intake and bonnet were separated from the engine.
- Two fan blades were fractured.
- A fan blade was fractured near the root.
- An adjacent fan blade was fractured at mid-span.
- Part of a blade was embedded in the containment ring.
- The remainder of the fan blades showed damage to the tips and leading edges.
The NTSB said it was too early to draw conclusions about the causes of the engine failure. Most of the damage was limited to the engine, and the aircraft sustained minor damage.
The investigation is ongoing. The cockpit voice recorder and flight data recorder are located in Washington, where the NTSB will analyze the data.
The 777 Series is an American twin-engine large-body commercial airliner manufactured by Boeing Commercial Airplanes. It is the largest jet in the world and started 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 has said. United say they have 24 of the 777s in service.
The United 777 plane in Saturday’s incident is 26 years old.
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SOURCE USA TODAY Network Reports and Research; National Bureau of Transportation Safety; 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.