Boeing 777: what caused an engine failure on a United Airlines flight over Denver - and is the B777 plane safe?

Boeing has grounded all 777 aeroplanes with the same Pratt and Whitney engine that failed and caught fire over Denver

An investigation has been launched into the safety of some Boeing 777 engines after one of its planes was forced into an emergency landing.

A United Airlines flight from Denver, bound for Honolulu, had to turn around when it suffered an engine failure - resulting in debris falling on a nearby residential area.

There has as yet been no injuries reported from the 231 passengers and 10 crew onboard the plane, and those on the ground from the incident on 20 February.

Fragments of a Boeing 777 engine sit scattered in a Denver neighbourhood after catching fire mid-air. An engine on the Boeing 777 exploded after takeoff prompting the flight to return to Denver International Airport where it landed safely. (Pic: Getty Images)

Boeing has recommended grounding dozens of its 777 aircrafts which have the same engine, as the Federal Aviation Administration (FAA) begins its investigation.

What engines are on the Boeing 777?

The aircraft which was forced into returning to Denver was powered by Pratt and Whitney 4000-112 engines, Boeing confirmed in a statement.

The engine manufacturer has sent a team to work with investigators.

There are 69 in-service and 59 in-storage Boeing 777 aircrafts with the same engine around the world - all of which the company recommends grounding.

Why did the Pratt and Whitney engine catch fire?

FAA administrator Steve Dickson said that all available data had been reviewed following the incident in Denver, and that further checks of the 777 aircrafts were being made.

"Based on the initial information, we 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 Boeing 777 airplanes,” he said.

Initial findings have determined that two fan blades in the aircraft’s right engine were fractured and other blades also impacted, according to the National Transportation Safety Board (NTSB).

Where are the affected Boeing 777 planes?

The United Airlines is the only US airline flying this 777 aircraft model, according to the FAA.

Its other planes with the same Pratt and Whitney engine are stationed in Japan and South Korea, totalling 128 aircrafts around the world.

Japan has already ordered for all 777s with the same engines to avoid its airspace until further notice and suspended its use by JAL and ANA airlines.

Which flights have had engine failures?

The United Airlines flight 328 which encountered the engine failure on 20 February was not the first incident involving a Pratt and Whitney engine.

In 2018, a United Airlines flight from San Francisco to Hawaii experienced a broken blade in its Pratt and Whitney 4000 series engine.

An engine exploded six minutes after take-off on a flight between Okinawa and Tokyo, forcing the aircraft to turn around.

And a cargo plane leaving the Netherlands also had one of its engines fail within minutes of taking off. No one was hurt in either of these incidents.

Are Pratt and Whitney plane engines safe?

A statement released by Pratt and Whitney following the incident over Denver, read: “United Airlines Flight 328 is currently under NTSB investigation and Pratt & Whitney has dispatched a team to work with investigators.

“Pratt & Whitney is actively coordinating with operators and regulators to support the revised inspection interval of the Pratt & Whitney PW4000 engines that power Boeing 777 aircraft.

“Any further investigative updates regarding this event will be at the discretion of the NTSB.

“Pratt & Whitney will continue to work to ensure the safe operation of the fleet.”