The mid-air engine fire that caused debris from a Boeing 777 to rain down over Denver on Saturday was caused by a damaged fan blade that had cracked through wear and tear, according to preliminary findings.
Federal investigators believe the fractured fan blade broke off the Pratt & Whitney engine and chipped off half of a second blade on its way out – with one piece later found on a soccer field in a Denver suburb.
The damage to the blade is consistent with metal fatigue, a preliminary assessment shows, after the PW400 engine failed with a ‘loud bang’ four minutes after takeoff from Denver on Saturday.
The recovered parts are being flown to a Pratt & Whitney laboratory and will be examined on Tuesday under the supervision of National Transportation Safety Board investigators, who will also probe maintenance records to see whether problems were overlooked during inspections.
Saturday’s near-disaster has also led to more than 100 Boeing 777s which use the same engines being grounded around the world, while the FAA has called for ramped-up checks on Pratt & Whitney’s fan blades.
The damaged-blade theory is reminiscent of a 2018 disaster on board a Southwest Airlines flight, when a broken fan blade triggered an explosion that smashed a window, killing a woman who was blown outside.
Investigators will compare the Denver mishap with the 2018 accident, but NTSB chief Robert Sumwalt said it was not yet clear whether Saturday’s failure was consistent with that disaster.
Sumwalt said the engine involved in Saturday’s incident had a ‘containment ring’ which did manage to hold in some of the parts as they were flying out, adding that there had been no structural damage to the plane.
While the early findings suggest that metal fatigue is a likely explanation for the fan blade failure, full-scale NTSB inquiries can take a year or longer to complete.
‘Our mission is to understand not only what happened but why it happened, so that we can keep it from happening again,’ Sumwalt said.
Investigation: The damaged starboard engine of the Boeing 777 involved in the near-disaster on board United Airlines Flight 328 is seen in a hangar at Denver International Airport on Monday
Parked: Boeing 777s stand at a production facility in Everett, Washington on Monday as more than 100 of the aircraft were grounded worldwide because of Saturday’s near-calamity in the skies over Denver
The fallout from Saturday’s incident has led to 69 in-service planes and another 59 in storage being grounded in the US, Japan and South Korea, the only countries with planes using this particular engine.
United Airlines, the only US carrier with affected planes, said it grounded 24 Boeing 777s and 28 others will remain parked.
Japanese regulators ordered Japan Airlines and All Nippon Airways to ground 32 planes, and South Korea’s Korean Air and Asiana Airlines said Monday they will ground their Boeing 777s.
FAA chief Stephen Dickson said inspectors quickly determined that inspections should be done more frequently for the type of hollow fan blades used in some Pratt & Whitney engines.
Safety experts were alarmed because debris blew off the disintegrating engine, creating shrapnel that can damage key systems like hydraulic lines or hit the passenger cabin.
‘That was a substantial hit,’ said John Goglia, a former NTSB member. ‘If that had hit the wing, things might have been different because the wing is full of fuel’ and the broken engine was still on fire.
Investigators will look at why the cowling, which covers the front of the engine, broke off along with other parts on the Hawaii-bound flight.
Another concern is that the engine remained on fire even after pilots presumably shut off its fuel supply. That could indicate a fuel leak, said Todd Curtis, a former Boeing engineer and now a safety consultant.
Mid-air panic: United Airlines Flight 328 on its way back to Denver International Airport on Saturday with its starboard engine on fire following the explosion shortly after takeoff
Grounded: Aircraft belonging to All Nippon Airways, a Japanese carrier which uses the same Pratt & Whitney engines on board its Boeing 777s, are seen in a file photo at Tokyo’s Haneda Airport
A map showing the Denver suburb of Broomfield in relation to the airport where the United Airlines flight had taken off and subsequently made an emergency landing
Two people are injured after Boeing cargo plane engine catches fire, dropping debris onto a Dutch town
Two people have been injured after the jet engine of a Boeing cargo plane burst into flames shortly after taking off in the Netherlands.
Debris from the 747-400 jet fell on the Dutch town of Meerssen on Sunday afternoon when it got into trouble shortly after taking off from Maastricht airport.
An elderly woman was left with a head injury after being hit by a piece of the engine while a young child burned their hand by picking up another bit of smoldering metal.
The 747 jet involved in the accident in the Netherlands was using a Pratt & Whitney PW4000 engine, a smaller version of one involved in the explosion over Denver.
Dutch safety inspectors said the 747 aircraft belonged to Bermuda-based Longtail Aviation and had taken off from Maastricht airport around 4.10pm on Sunday.
The aircraft was bound for New York JFK airport and was due to pass through UK airspace, skirting Sheffield and Manchester along the way.
But it got into trouble moments after takeoff, causing debris to rain from the sky.
Meerssen, where most of the debris was found, is located just two miles from the end of the runway in Maastricht.
The 30-year-old aircraft was diverted to Liege airport, in neighbouring Belgium, but spent some time circling above the Ardennes at 10,000ft to burn fuel and lose weight before landing.
The aircraft was heading to Honolulu on Saturday from Denver International Airport when debris struck the plane’s right engine shortly after takeoff, causing it to erupt into flames.
The captain had been giving an announcement over the intercom when a large explosion rocked the cabin, accompanied by a bright flash. Passengers recalled their horror as they looked out the window to see engine casing and chunks of fiberglass falling from the plane, and thick black smoke emanating from the wing.
The incident forced the pilot to pull off an emergency landing back in Denver just 20 minutes after take-off, at around 1.30pm local time.
Video recorded aboard Flight UA328 captured the moment it touched back down on the runway safely, prompting the cabin to erupt in applause and cheers of relief.
The NTSB said the cockpit voice recorder and flight data recorder were transported to its lab in Washington for the data to be downloaded and analyzed.
NTSB investigations can take up to a year or longer, although in major cases the agency generally releases some investigative material midway through the process.
Former National Transportation Safety Board Chairman Jim Hall called the incident another example of ‘cracks in our culture in aviation safety [that] need to be addressed’.
Hall, who was on the board from 1994 to 2001, has criticized the FAA over the past decade as ‘drifting toward letting the manufacturers provide the aviation oversight that the public was paying for’.
Investigators will compare Saturday’s incident, in which the 231 passengers and 10 crew were unhurt, with previous mishaps including the 2018 disaster in which a woman was killed.
The same year, another United Airlines Boeing 777 suffered an engine failure that caused parts of the housing to break off and fall into the Pacific Ocean as the plane flew from San Francisco to Honolulu.
In a report last year on the incident, the NTSB said Pratt & Whitney missed signs of cracking in previous inspections of the fan blade that broke, and faulted the company’s training. The company told the NTSB it was fixing the shortcomings.
In December last year, a Japan Airlines Boeing 777 with the same Pratt & Whitney engines suffered fan blade damage and lost a large panel.
The plane returned safely to Naha with none of the 178 passengers and 11 crew injured, but officials said at the time that the left engine experienced a malfunction at approximately 16,000-17,000 feet.
And on Saturday, hours before the Denver flight, a Boeing 747 cargo plane in the Netherlands suffered an engine failure that resulted in engine parts falling to the ground.
Although the plane has Pratt & Whitney engines, they are different from those on Boeing 777s, and nothing yet shows a link to the problem on the United plane, said a spokeswoman for the European Aviation Safety Agency.
The announcement came after the Federal Aviation Administration (FAA) said it would require stepped-up inspections of 777 aircraft with Pratt & Whitney PW4000 series engines after the right engine failure on United Flight 328
Pratt & Whitney, a subsidiary of Raytheon, is one of the major players in the aircraft-engine market along with Boston-based General Electric and Britain’s Rolls-Royce.
Cai von Rumohr, an aviation analyst with Cowen, said events around Saturday’s flight would be a bigger issue for Raytheon than for Boeing, whose reputation was battered by two deadly crashes in 2018 and 2019.
Boeing has said the aircraft should be taken out of service until federal regulators had determined an inspection procedure.
‘While the NTSB investigation is ongoing, we recommended suspending operations of the 69 in-service and 59 in-storage 777 aircraft powered by Pratt & Whitney 4000-112 engines,’ the company said.
Japan has requested airlines avoid using Boeing 777 planes with Pratt & Whitney 4000 engines for take-offs, landings and overflights in its territory until further notice, authorities said.
In Britain, transport secretary Grant Shapps announced on Monday morning that all Boeing 777s with PW4000 engines will be banned from flying over British airspace until further notice.
Pratt & Whitney meanwhile says it is ‘actively co-ordinating’ with planemakers and federal regulators, adding that it had dispatched a team to work with investigators looking at what went wrong on Saturday’s flight.
Terrified United Airlines passengers clapped in relief as their flight touched down safely in Denver on Saturday after suffering catastrophic engine failure
Video recorded by passengers aboard Flight UA328, which was carrying 231 travelers and 10 crew members, shows the engine on fire
Flames could be seen coming from the engine of the plane after it exploded at 15,000 feet
Greg Feith, a former NTSB air safety investigator, expressed his concern over not only how the engine came to be damaged in the first place, but that it caught fire and continued to burn until it landed
The Broomfield Police Department posted photos on Twitter showing large, circular pieces of debris leaning against a house in the suburb about 25 miles north of Denver
Cops in Broomfield responded to reports of objects falling from the sky on Saturday afternoon and saw huge metal objects in front lawns
On Sunday, the FAA had said it would require stepped-up inspections of all the 777s with Pratt & Whitney PW4000 series engines.
FAA administrator Steve Dickson said: ‘After consulting with my team of aviation safety experts about yesterday’s engine failure aboard a Boeing 777 airplane in Denver, I have directed them to issue an Emergency Airworthiness Directive that would require immediate or stepped-up inspections of Boeing 777 airplanes equipped with certain Pratt & Whitney PW4000 engines.
‘This will likely mean that some airplanes will be removed from service,’ he added.
Dickson said that his team has ‘reviewed all available safety data following [the] incident,’ and ‘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’.
According to Dickson, the FAA ‘is working closely with other civil aviation authorities to make this information available to affected operators in their jurisdictions’.
He said his team will be meeting with Pratt & Whitney and Boeing ‘to finalize the details of the Airworthiness Directive and any accompanying service bulletins to ensure that the appropriate airplanes are included in the order’.
This image provided by KCNC-TV in Denver shows the damage done when debris fell through the roof and into the kitchen of a home in Broomfield, Colorado on Saturday
Pieces of the aircraft landed on a football field as seen in the above image posted to Twitter by a local resident in Broomfield
Prior to Flight UA328 landing safely on Saturday, large chunks of debris had fallen from the plane on the Denver suburbs below, narrowly missing homes and other buildings.
Denver resident Kirby Klements was inside his home with his wife when they heard a huge booming sound.
A few seconds later, the couple saw a massive piece of debris fly past their window and into the bed of Klements’ truck, crushing the cab and pushing the vehicle into the dirt.
Another local resident, Kieran Cain, told CNN he was with his children at a nearby elementary school when the aircraft flew over. Seconds later, they heard a loud explosion.
‘We saw it go over, we heard the big explosion, we looked up, there was black smoke in the sky,’ Cain toldsaid.
‘Debris started raining down, which you know, sort of looked like it was floating down and not very heavy, but actually now looking at it, It’s giant metal pieces all over the place.
‘I was surprised that the plane sort of continued on uninterrupted, without really altering its trajectory or doing anything,’ he said.
‘It just kind of kept going the way it was going as if nothing happened.’
Flight 328 passenger David Delucia recalled for the Denver Post how he grabbed his wife’s hand after hearing the explosion, telling her: ‘We’re done for.’
‘The plane started shaking violently, and we lost altitude and we started going down,’ Delucia, who sat directly across the aisle from the side with the failed engine, said.
‘When it initially happened, I thought we were done. I thought we were going down. I thought we were going to die at one point,’ he said, adding that he and his wife took their wallets containing their driver’s licences and put them in their pockets so that ‘in case we did go down, we could be ID’d’.
Police in Broomfield released this photo showing debris from the United Airlines aircraft strewn across a football field
BOEING’S 737 MAX: WHAT WENT WRONG
OCT. 29, 2018 – A Lion Air 737 MAX plane crashes in Indonesia, killing all 189 people on board
NOV. 13, 2018 – FAA, Boeing say they are evaluating the need for software or design changes to 737 MAX jets following the Lion Air crash
NOV. 30, 2018 – Boeing is weighing plans to launch a software upgrade for its 737 MAX in six to eight weeks that would help address a scenario faced by crew of Indonesia’s Lion Air, sources told Reuters
MARCH 10, 2019 – An Ethiopian Airlines 737 MAX crashes, killing all 157 people on board
MARCH 12, 2019 – FAA says will mandate that Boeing implement design changes on the 737 MAX by April that have been in the works for months
MARCH 13, 2019 – FAA joins other major global regulators in grounding the 737 MAX, citing evidence of similarities between the two fatal crashes
APRIL 6, 2019 – Boeing says it will cut monthly 737 MAX production by nearly 20%; U.S. and airline officials say they believe the plane could be grounded for at least two months
MAY 16, 2019 – Boeing says it has completed a software update for its 737 MAX jets and is in the process of submitting a pilot training plan to the FAA
JUNE 27, 2019 – Boeing says it will take until at least September to fix a newly identified problem with software that emerged when FAA test pilots were reviewing potential failure scenarios of the flight control computer in a 737 MAX simulator
JULY 18, 2019 – Boeing says it has assumed regulatory approval of the 737 MAX’s return to service in the United States and other jurisdictions will begin early in the fourth quarter
OCT. 24, 2019 – Boeing says it still expects FAA approval to fly the 737 MAX in the fourth quarter, sending its shares higher despite a slump in quarterly profit. FAA says it will need “several weeks” for review
NOV. 7, 2019 – U.S. and European regulators ask Boeing to revise documentation on its proposed 737 MAX software fix
NOV. 11, 2019 – Boeing says it expects the FAA to issue an order approving the plane’s return to flight in December, forecasting commercial flights to resume in January
NOV. 15, 2019 – The head of the FAA tells his team to ‘take whatever time is needed’ in their review of the 737 MAX
DEC. 11, 2019 – FAA chief Steve Dickson says 737 MAX will not be cleared to fly before the end of 2019
DEC. 12, 2019 – Boeing abandons its goal of winning regulatory approval for the 737 MAX to resume flying in December after the U.S. Federal Aviation Administration (FAA) said the plane would not be cleared to fly before 2020
DEC. 23, 2019 – Boeing fires CEO Dennis Muilenburg
JAN. 6, 2020 – An audit conducted in December reveals that wiring in the tail of the 737 MAX could short circuit and lead to a crash if pilots don’t know how to respond correctly
JAN. 9, 2020 – Boeing releases hundreds of internal messages between employees to the Congress and the FAA last week, raising serious questions about its development of simulators and showing employees may have covered up issues
JAN. 13, 2020 – Budget airliner Ryanair reveals it could receive its first deliveries of up to 10 grounded 737 MAX aircraft from Boeing by April, but cautions this will depend on the regulators
JAN. 16, 2020 – Committee, appointed by Transportation Secretary Elaine Chao in April, finds the FAA safety approval process was not at fault
JAN. 21, 2020 – Boeing announces it does not expect federal regulators to approve its changes to the grounded 737 Max until this summer, several months longer than the company was saying just a few weeks ago.
“The bigger concern, besides the parts coming off, is the fact is there is this post-event fire.”
— TODAY (@TODAYshow) February 22, 2021
The image above shows smoke emanating from the damaged engine on the left
TROUBLED HISTORY OF THE ‘TRIPLE SEVEN’: A TIMELINE OF BOEING 777’S WORST ACCIDENTS
Since the American-made Boeing 777 wide-body jet airliner made its maiden flight in June 1994, it has been involved in 29 aviation incidents and accidents that have claimed the lives of 541 people.
Of these, three were hijackings while eight involved hull losses – or ‘total loss’ of the aircraft.
Five of the hull losses were in-flight while three were on-ground incidents.
British Airways Flight 38 – January 17, 2008
Crash investigators inspect wreckage and debris from grounded British Airways Flight 38 at Heathrow Airport on January 18, 2008
A British Airways plane crash-landed at Heathrow Airport, slightly injuring 47 passengers and triggering an inquiry into why the Boeing 777 flying in from Beijing landed short of the runway.
Fire engines smothered the aircraft in foam after the landing at the world’s busiest international airport extensively damaged its wings and ripped off its undercarriage.
Aviation commentators said the fact that the plane only just cleared the perimeter fence, hit the ground well short of the runway and then slid to a halt pointed to a massive loss of power in the final stages of landing.
The wheels of the plane, which had a routine maintenance check just a month prior, were still in the field where it crashed, several hundred yards from the runway.
There were no fatalities.
EgyptAir Flight 667 – July 29, 2011
The image above shows damage on the nose section of EgyptAir Flight 667 in Cairo after a fire tore through the cockpit before it was set to depart for Jeddah, Saudi Arabia in July 2011
An EgyptAir Boeing 777-200 was evacuated at Cairo International Airport after a fire started in the cockpit while preparing to depart.
All 307 passengers survived but the fire, thought to have been started by an electrical fault, damaged the plane beyond repair.
Seven people were treated for smoke inhalation. The flight was destined to land in Jeddah, Saudi Arabia.
Asiana Airlines Flight 214 – July 6, 2013
The wreckage of Asiana Flight 214 lies on the ground after it crashed at the San Francisco International Airport in San Francisco in this July 6, 2013 aerial photo
Two teenage girls were killed and more than 180 people were injured when a flight operated by South Korean carrier Asiana Airlines crashed while landing at San Francisco airport.
Two passengers who were not wearing seatbelts were ejected from the aircraft during the crash and were killed.
The Boeing 777, which was carrying 291 passengers and 16 crew, was flown from Seoul to San Francisco.
An investigation by the National Transportation Safety Board faulted the pilots and crew for relying too much on automated systems and for incorrectly flying the plane during landing.
Malaysia Airlines Flight 370 – March 8, 2014
Malaysia Airlines flight MH370 became one of the world’s greatest aviation mysteries when it vanished on its way from Kuala Lumpur to Beijing on March 8, 2014.
The Boeing 777-200ER went missing with 239 people on board. Malaysia, China, and Australia called off a two-year $130million underwater search in the southern Indian Ocean in January 2017 after finding no trace of the aircraft.
A second three-month search, led by Ocean Infinity, ended similarly in May the following year.
Malaysia Airlines Flight 17 – July 17, 2014
Recovery workers in rebel-controlled eastern Ukraine load debris from the crash site of Malaysia Airlines Flight 17 in November 2014 – four months after the plane was shot down
Malaysia Airlines flight MH17 was flying from Amsterdam to Kuala Lumpur on July 17, 2014 when it was shot down by a missile fired from territory held by pro-Moscow rebels amid fighting in eastern Ukraine, killing all 298 aboard. Russia has denied any involvement.
A Dutch-led international Joint Investigation (JIT) team spent years collecting evidence before issuing arrest warrants in 2019 for the four suspects: Russians Sergey Dubinsky, Oleg Pulatov and Igor Girkin, and Ukrainian Leonid Kharchenko.
A hearing on the merits of the trial is scheduled to start this month.
British Airways Flight 2276 – September 8, 2015
The image above from September 2015 shows a British Airways Boeing 777 airliner burst into flames on the runway at Las Vegas McCarran Airport
A British Airways jetliner engine caught fire in Las Vegas as the plane was about to take off for London, forcing all 172 passengers and crew to escape down emergency slides as smoke and flames engulfed the aircraft.
Several passengers needed hospital treatment for minor injuries after the Boeing 777’s aborted takeoff, with one of those present saying smoke caused people to rush to the front of the plane, sparking scenes of panic.
Singapore Airlines Flight 368 – June 26, 2016
A Singapore Airlines Ltd (SIA) flight to Milan caught fire after returning to Singapore’s Changi airport following an engine oil warning message, but all passengers were safe.
The aircraft’s right engine caught fire after the aircraft, a Boeing 777-300ER, touched down at Changi airport at around 6:50am on June 26, 2016. Emergency services put out the fire and there were no injuries to the 222 passengers and 19 crew on board.
The SIA flight, SQ368, departed at 2:05am, but about two hours into the flight the pilot announced there was an engine problem and the flight would return to Singapore.
Emirates Flight 521 – August 3, 2016
The image above shows Emirates Flight 521 after it crashed while attempting to abort a landing in Dubai after flying in from India in August 2016
An Emirates passenger jet crashed while attempting to abort a landing in Dubai
All 300 passengers and crew were safely evacuated but a firefighter died tackling flames after the Boeing 777-300, arriving from India, caught fire after skidding along the Dubai airport runway on its fuselage.
It was the first major accident in Emirates’ more-than-30-year history.
All 300 passengers and crew safely evacuated the jet but a firefighter died tackling flames after the Boeing 777-300, arriving from India, caught fire after skidding along the Dubai airport runway on its fuselage.
Investigators said the pilot failed to notice that the Boeing 777’s engine thrust settings remained too low and cut short a procedure.
Ethiopian Airlines cargo plane on the ground in Shanghai – July 22, 2020
Terrifying footage has captured the moment a Boeing 777 engulfed by a huge blaze and smoke at an airport in China. The Ethiopian Airlines cargo plane caught fire at around 4pm on July 22, 2020
A Boeing 777 plane burst into flames today in front of shocked passengers while being parked in one of the busiest airports in China.
The cargo plane belonging to Ethiopian Airlines caught fire at around 4pm local time on the tarmac of Shanghai Pudong International Airport, according to authorities.
The fire was put off about an hour later, said the local authorities. No injuries or deaths were reported.
Shocking footage shows smoke and flames engulfing the Boeing 777 while several emergency vehicles were rushing towards the burning aircraft.