DENVER – Sound boomed in the sky above Broomfield on Saturday afternoon. What followed was something just as unnatural and dangerous: small and large parts of a huge turbine engine began to rain in the neighborhoods below the flight route of United Airlines flight 328.
“We looked up at the sky and saw a lot of dark smoke and things raining down from the sky,” Lisa Hill told Denver7, who was walking in an open space near her home. “We thought that maybe the birds hit the engine and those were the little things that we saw falling, but actually they were big things, they seemed small a few kilometers away.”
The Boeing 777-200, en route to Honolulu, suffered a failure in the right engine shortly after takeoff. The plane turned around and returned to Denver International Airport, landing safely. No one on board or on the ground was injured.
But what caused an engine failure not contained so spectacularly? Researchers will look for that answer to such a rare event in the coming months. But Tom Haueter, a consultant for ABC News and a former NTSB director of the Office of Aviation Safety, has some ideas about what they might be looking for.
“What the investigators are going to look at, collect all the parts, look at the photos, take a look at the engine maintenance records, the engine history, when it was done, what is the service life, how many hours is it in, how many cycles how many flights were on it, start collecting all the information, ”Haueter told ABC News.
Soon after the incident, photos and videos began to appear on social media. For aviation experts like Haueter, these posts offered 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 the big blades that you can see when you’re looking at the outside engine, a piece of the fan blade is missing, and I can’t say another photograph if there is another fan blade completely missing, ”said Haueter.
The wreckage of the engine fell over a wide area of Broomfield, affecting homes and properties in the Northmoor and Red Leaf neighborhoods. Pieces were seen scattered across parks, lawns and roofs. But Haueter said one of the most important pieces that the authorities need to find is the missing fan blade.
“The really important piece to recover would be the fan blade, or pieces of the fan blade. You want to have both sides of the fault so you can say, ‘OK, here’s what happened.’ Was there a cut in the blade? Was there a blade failure? Was anything else going on? There are many pieces, but only a few are really critical for the investigation, ”he said.
Video captured by a passenger aboard flight 328 on Saturday showed engine failure in flight before pilots made an emergency landing. Passengers probably felt the explosion and vibrations until the DIA.
“Well, basically when something like this happens, the engine is extremely unbalanced. The turbine engines are designed with all that massive rotation to be very smooth, obviously. When you lose a piece of that, now you have a lot of vibration going on. The parts start to rub together that don’t normally rub, you start to vibrate the loose parts into the fuel system, so suddenly you may have a crack in the fuel line, ”said Haueter. “You have the friction of this massive engine that is still spinning and is destroying several pieces of metal while you are doing it. It looks very dramatic, let’s be honest, but that, unless the engine really catches on fire and there’s a big fire going on, it looks worse than it is. “
Investigators will not know exactly what happened until they destroy the engine. A National Transportation Safety Board team is heading to the area to take over the investigation, police said.
Although Haueter said that what happened on Saturday is very rare, some are taking no chances. Japan’s Ministry of Transport has instructed Japan Airlines and All Nippon Airways, which operate aircraft equipped with the same series of engines, to land the Boeing 777s in their fleet.
The transport ministry also refers to a “serious incident” that occurred on a Japan Airlines flight on December 4 last year, where the same type of engine (Pratt & Whitney PW4000 series) was damaged.