DENVER – The sound hovered over the sky above Broomfield on Saturday afternoon. What followed was just as unnatural and dangerous: small and large pieces of a massive turbine engine began to rain in the neighborhoods below United Airlines Flight 328.
“We looked up at the sky and saw a lot of black smoke and rain from the sky,” Lisa Hill told Denver7, who was walking in an open space near her home. “We thought maybe the birds hit the engine and those were the little things we saw falling, but they were really big things, they just looked small from a few miles away.”
The Boeing 777-200, which was heading to Honolulu, just suffered an engine failure shortly after takeoff. The plane returned and returned to Denver International Airport, landing safely. No one on board or on the ground was injured.
But what caused such a spectacular, relentless engine failure? Investigators will look for that answer to such a rare event in the coming months. But Tom Haueter, an ABC News consultant and former NTSB director of the Aviation Safety Bureau, has some perspective on what he might be looking for.
“What the investigators will analyze, they will collect all the parts, they will look at the photos, they will take a look at the engine maintenance records, the engine history, when it was done, what is the lifespan, how many hours are on it, how many cycles, how many flights were on him, they are starting to collect all the information, “Haueter told ABC News.
Shortly after the incident, photos and videos began to appear on social media. For aviation experts like Haueter, these posts provided a clue as to what might have happened.
“Looking at the photos I saw, it looks like a piece of one of the fan blades, these are big blades that you can see when you look from the engine from the outside, a piece of a fan blade is missing, and I don’t know from another photo if another fan blade is completely missing “, said Haueter.
Engine debris fell on a large area of Broomfield, affecting homes and properties in the Northmoor and Red Leaf neighborhoods. Parts were seen scattered in parks, lawns and on rooftops. But Haueter said one of the most important parts authorities need to find is the missing fan blade.
“The really important part of getting back would be the fan blade or pieces of the fan blade. You want to have two parts of the failure, so you can say “OK, here’s what happened.” Was there a nick in the blade? Was there a defect in the blade? Is anything else happening? There are a lot of pieces, but only a few pieces are really critical for the investigation, “he said.
A video recorded by a passenger on board a 328 flight on Saturday showed the engine crashing in flight before the pilots made an emergency landing. Passengers probably felt the explosion and vibrations until the DIA.
“Well, practically when something like this happens, the engine is extremely unbalanced. Turbine engines are designed with all those massive spins to be very smooth, obviously. When you lose some of that, you have a lot of vibration. The parts start to rub together, which don’t normally rub, you start vibrating the free parts for the fuel system, so all of a sudden you can have a crack in the fuel line, ”Haueter said. “You have friction from this massive grinding of the engine that still spins and destroys various pieces of metal as it does so. It looks pretty dramatic, let’s be honest, but unless the engine really catches fire and has a major fire, it looks worse than it is. ”
Investigators will not know exactly what happened until they break the engine. A team from the National Transportation Safety Council is heading to the area to take over the investigation, police said.
Although Haueter said that what happened on Saturday is very rare, some do not risk it. The Japanese Ministry of Transportation has instructed Japan Airlines and All Nippon Airways, which operate aircraft equipped with the same series of engines, to land a Boeing 777 in their fleet.
The Ministry of Transport also refers to a “serious incident” that took place on a Japan Airlines flight on December 4 last year, in which the same type of engine (Pratt & Whitney PW4000 series) was damaged.