DENVER – The noise rumbled through the air above Broomfield Saturday afternoon. What followed was something equally unnatural and dangerous: Small and large pieces of a huge turbine engine began to rain on neighborhoods below the flight path of United Airlines Flight 328.
“We looked at the sky and saw a lot of dark smoke and things raining from the sky,” Lisa Hill told Denver7, who walked into an open space near her house. “We thought birds were going to hit the engine and those were the little things we saw falling, but they were actually big things, they just looked small from a few miles away.”
The Boeing 777-200, bound for Honolulu, experienced a malfunction in the right engine just shortly after takeoff. The plane turned and returned safely to Denver International Airport. No one on board or on the ground was injured.
But what caused such a spectacular, incessant engine failure? Researchers will be looking for that answer to such a rare event in the coming months. But Tom Haueter, ABC News consultant and former NTSB director of the Office of Aviation Safety, has some insight into what they might be looking for.
“What the researchers are looking at, collecting all the parts, looking at the pictures, looking at the maintenance data of the engine, the history of the engine, when was it made, what is the lifespan, how many hours are on it? , how many cycles, how many flights were on it, start collecting all the information, ”Haueter told ABC News.
Shortly after the incident, photos and videos appeared on social media. For aviation experts like Haueter, those posts provided an idea of what might have happened.
“Looking at the pictures I have seen, it turns out that there is a piece of one of the fan blades, which is the large blades that you can see from the outside of the motor, there is a piece of a fan blade missing, and I can can’t tell from another photo if another fan blade is completely missing, ”said Haueter.
Engine debris fell on much of Broomfield, affecting homes and properties in the Northmoor and Red Leaf neighborhoods. Parts were seen scattered in parks, lawns and on roofs. But Haueter said one of the most important pieces for authorities to find is the missing fan blade.
“The really important part to come back is the fan blade or pieces of the fan blade. You want to have two sides of the failure so you can say, “OK, here’s what happened.” Is there a notch in the blade? Was there a mistake in the knife? Was there anything else going on? There are many pieces, but only a few pieces are really crucial to the research, ”he said.
Video taken by a passenger aboard Flight 328 on Saturday showed the engine failure on board before pilots made an emergency landing. Passengers likely felt the explosion and vibrations all the way back to DIA.
“Well, when something like this happens, the engine is essentially out of balance. Turbine engines are designed with all those huge rotations to be very smooth of course. If you lose some of that, you now have a lot of vibrations. Parts start to rub together that don’t normally rub, you start to vibrate parts loose for the fuel system, so suddenly a fuel line can burst, ”said Haueter. “You have friction from this huge grinding of the motor that is still spinning and it is destroying various pieces of metal while it is going. It looks pretty dramatic, let’s be honest, but unless the bike really catches fire and a big fire is going on, it looks worse than it is. “
Investigators don’t know exactly what happened until they take the engine apart. A team from the National Transportation Safety Board is going to the area to take over the investigation, police said.
While Haueter said what happened on Saturday is very rare, some aren’t taking any chances. Japan’s Ministry of Transport ordered Japan Airlines and All Nippon Airways, which operate planes with the same series of engines, to ground the Boeing 777s in their fleet.
The Department of Transportation also refers to a “serious incident” that occurred during a Japan Airlines flight on December 4 last year in which the same type of engine (Pratt & Whitney PW4000 series) was damaged.