United's Boeing 777 showers debris across Colorado after engine failure

Preliminary evidence suggests one of the large fan blades that rotate at the front of the engine broke loose

United Airlines flight UA328, carrying 231 passengers and 10 crew on board, returns to Denver International Airport with one of its engines on fire. Reuters

Police tape blocks a street where debris fallen from the United Airlines aircraft's engine lay scattered through the neighbourhood of Broomfield, outside Denver, Colorado. AFP

United Airlines said no one on board the aircraft was injured in the incident. AFP

The plane was headed from Denver to Honolulu when the incident occurred around 1.30pm local time. AP

Early investigations found one of the large fan blades that rotate at the front of the engine broke loose. AP

Photos on television and social media showed large chunks of plane parts strewn across in the city. AP

Police said debris landed in two neighbourhoods and in a local park. AFP

Parts of the plane's engine fell on busy roads. AFP

Construction crews survey damage from the debris at a property in Broomfield. AFP

A Boeing 777-200 operated by United Airlines made an emergency return to Denver International Airport on Saturday following an engine failure that rained debris on a city suburb. The airline said no-one aboard was injured.

United Flight 328 was headed from Denver to Honolulu when the incident occurred around 1.30pm local time, Federal Aviation Administration spokesman Allen Kenitzer said. The plane landed safely back at Denver after its right engine failed, the FAA said in a statement. The FAA and the National Transportation Safety Board will investigate.

Preliminary evidence suggested that one of the large fan blades that rotate at the front of the engine broke loose, said a person familiar with the incident who wasn’t permitted to speak publicly about it. The violent failure prompted debris to break loose, the person said.

"I’m honestly shocked, looking at this debris field," Rachel Welte, a police spokeswoman in Broomfield, Colorado, said at a news conference. Television and social-media images showed large chunks of plane parts strewn across in the city. Police said debris landed in two neighbourhoods and in a local park.

The flight had 231 passengers and 10 crew members aboard and was met by emergency crews as a precaution, David Gonzalez, a United spokesman, said.

The plane departed Denver at 12.15pm and returned around 1.30pm, airport spokeswoman Alex Renteria said by phone. It took off toward the west and reached an altitude of more than 13,000 feet (3,963 metres) before circling around to land, according to the flight-tracking website Flightradar24.

Flightradar24 listed the plane’s tail number as N772UA, a Boeing 777 manufactured in 1995, according to FAA records.

Last year, the NTSB concluded that a previous engine failure on a United 777 was the result of inadequate test standards at the engine manufacturer, Raytheon Technologies’s Pratt & Whitney division, to ensure metal used in fan blades didn’t contain imperfections.

After the incident, Pratt re-inspected all 9,600 fan blades on the same model engine and didn’t find any others with potential safety problems, the NTSB said.

Boeing is referring questions to United, spokesman Gordon Johndroe said by email. Pratt & Whitney didn’t immediately respond to messages seeking comment.

Photos of the engine taken by passengers suggest it failed in a dangerous manner that may have allowed debris to fly out laterally, potentially putting the plane and the people inside at risk. The recent failure of an engine on a Hawaii-bound jet also elevates the potential severity of the incident.

"We’ve experienced an engine failure. We need to turn," one of the United 328 pilots radioed an air-traffic controller as the plane was climbing after takeoff, according to a recording posted on the LiveATC website.

Seconds later, he issued the standard emergency declaration: "Mayday, mayday."

The controller turned the jet to the left so it could return for a landing. When asked if they wanted to fly directly back to the airport, the pilot asked for a slightly longer route. "We need to run some check lists," he said.

All twin-engine aircraft are designed to be flown in the event that one of the jets fails, and planes have special fire extinguishers for engines. Pilots are trained on handling engine failures and repeatedly drilled on it.

Planes that fly long distances over oceans, such as the haul to Hawaii, must have enhanced engine maintenance and lower failure rates because they have fewer options for making emergency landings.

All jet engines are designed with a hardened exterior designed to prevent shrapnel from escaping except through the rear. If that containment system breaks down, it’s considered a rare so-called uncontained failure.

An engine failure on a Southwest Airlines 737-700 in 2018, in which debris that caromed into a window on the plane resulted in the most recent fatality of a passenger on a US flight.

Engine debris also showered a United flight from San Francisco to Honolulu on February 13, 2018. The Boeing 777-200, equipped with Pratt & Whitney engines, made an emergency landing. There were no injuries.