Following what is believed to have been an uncontained engine failure of the world’s first Triple Seven to enter service, Key.Aero compiles the facts of the flight including what the initial inspection from the NTSB found
A United Airlines Boeing 777 experienced an engine failure shortly after take-off from Denver International on Saturday (February 20).
The widebody, N772UA (c/n 26930) returned and landed safely at the facility and was met my emergency crews. There were no reported injuries onboard.
Flight 328 was a service between the capital of Colorado and Honolulu in Hawaii.
The failure – which appears to have been uncontained – left debris strewn across a Denver neighbourhood. Large parts of the engine cowling including the inlet cowl fell in residents’ gardens.
A video appeared on social media shortly after, showing the right-hand powerplant of the jet partially on fire and oscillating, without its cowling.
Uniform Alpha is a 777-200 and was the very first example of the twin-engine widebody to be delivered to any airline.
As the launch customer for the type, United accepted the aircraft on May 15, 1995, and began operating it on June 7.
The Boeing-built jet was the fifth ever to be produced and first flew on November 19, 1994.
Powered by two Pratt & Whitney PW4000 turbofan engines, the twinjet was laid out with capacity for 364 passengers in a two-class configuration.
The flight was carrying 229 passengers and ten crew members.
Since 2016, United has used the type exclusively for domestic operations including routes to and from Hawaii. In previous months, Uniform Alpha had almost entirely been conducting services across the Pacific to Honolulu and Guam.
Following the incident, United said in a statement on social media that it was “voluntarily and temporarily removing 24 Boeing 777 aircraft powered by Pratt & Whitney 4000 series engines from our schedule”.
The statement added: “We will continue to work closely with regulators to determine any additional steps and expect only a small number of customers to be inconvenienced.
“Safety remains our highest priority, which is why our crews take part in extensive training to prepare and manage incidents like UA328. We remain proud of our employees' professionalism and steadfast dedication to safety every day.”
US manufacturer Boeing said it was “actively monitoring recent events” and that while the NTSB investigation is ongoing, “we recommended suspending operations of the 69 in-service and 59 in-storage 777s powered by Pratt & Whitney 4000-112 engines until the FAA identifies the appropriate inspection protocol.”
Both Japan’s Civil Aviation Bureau and the Federal Aviation Administration have grounded 777s powered by the select PW4000 engine. Boeing said it supports these decisions.
It added: “We are working with these regulators as they take actions while these planes are on the ground and further inspections are conducted by Pratt & Whitney.”
Steve Dickson, the FAA’s administrator said: “After consulting with my team of aviation safety experts about yesterday’s engine failure onboard a Boeing 777 airplane in Denver, I have directed them to issue and Emergency Airworthiness Directive that would require immediate or stepped-up inspections of Boeing 777 airplanes equipped with certain Pratt & Whitney PW4000 engines.
After reviewing all available safety data, Dickson concluded that the inspection interval should be stepped up for the hollow fan blades that are unique to this model of engine, used solely on the 777.
In a statement on Sunday (February 21), the NTSB revealed that an initial examination of the aircraft indicated most of the damage was confined to the number two engine – the jet itself sustained minor damage. The examination and documentation of the airframe is ongoing.
Preliminary inspections of the Pratt & Whitney powerplant revealed: “The inlet and cowling separated from the engine,” and “Two fan blades were fractured”.
According to the NTSB, one fan blade was fractured near the root and an adjacent blade was fractured about mid-span.
A portion of one was embedded in the containment ring and the remainder of the fan blades exhibited damage to the tips and leading edges.
Investigators are expected to continue examining the engine, aircraft and photographs and video taken by passengers aboard flight 328.