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The likely reason why a United Airlines plane’s engine exploded over Denver – Colorado Springs, Colorado

Colorado Springs, Colorado 2021-02-23 13:51:32 –

By David Koenig, Associated Press

An investigation into the engine explosion of a jet airliner taking off from Denver focuses on fan blades that appear to have been weakened by wear, a development reminiscent of a catastrophic failure on another plane in 2018. ..

These and other recent engine failures question long-standing assumptions about fan blade life and whether fan blades are inspected often enough.

The Boeing 777, operated by United Airlines, had to make an emergency landing in Denver after one of its engines exploded, ejecting a large amount of debris that landed in the neighborhood and sports fields. Passengers captured a video of a crippled engine wobbling and still burning when the pilot safely returned to the airport minutes after the plane to Hawaii took off.

what happened?

Investigators said at the end of Monday that two fan blades on the Pratt & Whitney engine broke, one of which showed signs of metal fatigue or hairline cracks due to wear stress. They believe that the weakened blade broke first, then half of the adjacent blades were missing.

National Transportation Safety Board Chairman Robert Samwalt said authorities investigators would investigate engine and fan blade maintenance records. He said fan blade parts, including those found on a soccer field outside Denver, will be inspected at the Pratt & Whitney Institute on Tuesday.

Stephen Dixon, head of the Federal Aviation Administration, said inspectors more often inspect the hollow fan blade types of certain Pratt & Whitney engines used on some Boeing 777s. He said he immediately decided that he needed it.

As a result, 69 planes and 59 storage locations were grounded in the United States, Japan, and South Korea, the only countries that own planes that use this particular engine. United, the only US aircraft carrier with affected planes, said it would ground 24 Boeing 777s and leave the other 28 parked. Japanese regulators have ordered Japan Airlines and All Nippon Airways to land 32 aircraft, and South Korean Air and Asiana Airlines have announced that they will land the Boeing 777 on Monday.

What are the investigators looking for?

According to safety experts, the investigation should be done differently, depending on why the fan blade broke (whether there was a mistake in manufacturing or maintenance, or if the problem was overlooked during the inspection). The focus is on whether it needs to be done more often. They compare Saturday’s case with December in Japan and a similar case in 2018 with another United Airlines to Hawaii.

Investigators will also investigate why the cowling covering the front of the engine broke along with other parts. The photo shows a large rift in the fairing. This is a composite material that makes the plane more aerodynamic by smoothing the joints where the body meets the wings.

“It was a big blow,” said John Goglia, a former member of the National Transportation Safety Board investigating the case on Saturday. “If it hit the wing, the situation might have been different because the wing was full of fuel,” and the broken engine was still burning.

However, Samwalt said the plane “had no structural damage.”

Another concern: The engine continued to burn, perhaps even after the pilot cut off the fuel supply. Former Boeing engineer and now safety consultant Todd Curtis said this could indicate a fuel leak.

How dangerous were the passengers?

Safety experts were wary of creating debris that could be blown from a collapsing engine, damaging key systems such as hydraulic lines, or colliding with the cabin.

The last accident-related death on a US airline flight occurred in 2018. A broken fan blade caused an engine failure on a Southwest Airlines Boeing 737. A part of the engine housing collided and the window broke. Passengers in the window seats were blown off on the way outside and died of injuries. The engine was manufactured by CFM International, a joint venture between General Electric and Safran SA in France.

On Saturday, none of the 231 passengers or 10 crew members were injured.

Did you have a similar incident?

A few hours before Denver’s flight, a Dutch Boeing 747 freighter suffered an engine failure and engine parts fell to the ground. The plane is equipped with a Pratt & Whitney engine, but unlike the Boeing 777 engine, no similarity to the United plane problem has yet been shown, a European Union Aviation Safety Agency spokeswoman said. Janet North Court said.

However, other accidents seem to be closely related to the Denver case.

More: Four important things to know about United Airlines flights that have debris in the Denver area

In December, Japan Airlines’ Boeing 777, equipped with the Pratt & Whitney engine of the same series, suffered damage to its fan blades and lost a large panel, but was able to land safely.

In 2018, another United Airlines Boeing 777 suffered an engine failure, and when the plane flew from San Francisco to Honolulu, part of its home broke and fell into the Pacific Ocean. In a report on last year’s incident, the NTSB said Pratt & Whitney failed to train the company after missing signs of cracking in a previous inspection of a broken fan blade. The company told the NTSB that it has fixed the shortcomings.

Does this hurt Boeing?

Cowen’s aviation analyst Kai von Lemor said Saturday’s pre- and post-flight events would be more of a problem for Pratt & Whitney’s parent company Raytheon than for Boeing. Still, it affects a relatively small number of planes, and the engine has been in use for many years, so he said it was “probably not a big negative” for Raytheon.

Boeing may also be in the limelight as investigators are investigating why Cowling separated from the engine, other experts said. “The cowling was designed by Boeing, not by the engine maker,” said Jeff Gusetti, a former director of the FAA’s accident investigation department.

Boeing’s reputation has been hit by two deadly crashes on another plane, the 737 Max, since 2018.

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