The emergency order includes 777 Pratt & Whitney-powered aircraft transported by United Airlines, which had already voluntarily flown 24 aircraft after two broken fan blades sent metal pieces to its fuselage, such as yards, homes. truck և football field inside.
The planes were decommissioned in South Korea and Japan, where an engine-like malfunction with a Japan Airlines plane in December forced pilots to return to Okinawa. Boeing offered ground-based aircraft with the same type of engine.
The FAA said Tuesday’s order was an intermediate step and more action is expected. The agency noted that although the United F8 328 flight landed safely, the malfunction of the fan blade “led to engine damage, fire during the flight, damage to the aircraft”, creating unsafe conditions.
“As these necessary inspections continue, the FAA will review the results on a rolling stock basis,” the agency said in a statement, adding that it could also review the inquiry requirements.
Boeing said Tuesday night that it supported the move: “The process will work with our customers.” According to the company, there are 128,777 aircraft with affected engines in the world, 69 of which are in operation and the rest are spare.
United said it would comply with the order to “ensure that all 52 aircraft in our fleet are under strict safety standards.”
In February 2018, another United 777 pilot, who was also heading to Honolulu with the same engine, had to make an emergency landing after the fan blade broke and large pieces of engine cover were cut. The National Transportation Safety Board found that the fracture was most likely the result of problems with the Pratt & Whitney inspection process, which the company said had improved.
Following the 2018 incident, the FAA ordered new և periodic inspections of engines based on how many times they were used. The FAA said that “these thresholds provide an acceptable level of security,” according to 2019. On Sunday, FAA Administrator Steve Dixon said the agency had concluded that “the inspection range should be strengthened.”
Tuesday’s order, known as the Emergency Fitness Command, requires a test process known as thermal acoustics imaging, or TAI, used to detect cracks. It uses sound energy to generate heat, and the resulting images are checked by inspectors, according to the NTSB.
“TAI technology can detect cracks on the inner surfaces of cavity vents or in areas that may not be visible during visual inspection,” the FAA said in a statement.
NTSB President Robert Sumwalt said this week that a preliminary examination of a single fan blade in an incident on Saturday “shows damage due to metal fatigue”, although the cause remains unclear. A team of investigators is analyzing engine-related debris that fell in Bromfield, west of Denver, spilling notes to determine the age of the fan blades when they were last inspected. He said earlier incidents involving Pratt & Whitney engines would be part of their investigation.
Sumwalt also said that investigators wanted to understand why the fan cup had torn off the plane, which is a possible problem that, according to external aviation security experts, is part of similar incidents in recent years.
According to the design, these pieces should not be cut, even if the fan blade is broken, because it is dangerous for those inside the plane. In 2018, the metal-mechanical mechanism of a south-west plane fan flew after a fan blade broke through a window and exploded, killing Jennifer Riordan, a mother of two in Albuquerque.
Sumwalt said it was too early to know the latest cause of the recent problem near Denver. But the agency’s investigation into the 2018 incident, which has some similarities, provides a window into the difficulties that may be associated with inspecting the fan blades for small but potentially catastrophic cracks.
From San Francisco International Airport to the Hawaiian Islands in 2018 The failed blade was inspected twice during the flight վել was considered safe in 2010 և 2015. The NTSB said this after the investigation of the incident. Pratt & Whitney used thermal sound imaging for these tests.
Investigators said that in 2010, the inspection tool found “a small indication” in the same place where the blade finally broke in 2018. In 2015, the tool found “greater instruction” in the same area.
But both times the inspectors thought what they saw was a “paint defect” used in the inspection process itself, according to the NTSB, which the agency failed to attribute to insufficient training and a wider lack of feedback from engineers on inspectors’ results. According to the long-term inspector who examined the blade, he said: “According to him, he will never find out if the knife is really cracked or if it is a false positive.”
Another hazard was found in the sunlight shining through large windows at Pratt & Whitney’s East Hartford, Conn., Overhaul facility. The test tool selects temperature changes. “During the day, thermal imaging would produce ghost images,” according to the NTSB.
Prior to the 2018 flight, test failures were based on Pratt & Whitney’s decision to classify the imaging process, which the company developed in 2005 as a “emerging technology,” according to the NTSB’s June 2020 report. This meant that the company “did not have to develop a formal program for initial, regular training”, inspector certification, and increased oversight, as would some other inspection methods, the NTSB said.
The inspectors who worked on the problem blade have undergone modest initial training, according to the NTSB. But for another course offered by Pratt, the two inspectors “were not allowed to attend so they could work to clean the blades of the fans in the store.”
Following the 2018 incident, the company announced that it had developed a curriculum for “pre-regular” courses for tests using thermal acoustics, the NTSB said.
Responding to Saturday’s incident in Colorado, Pratt & Whitney, a division of Raytheon Technologies, said it had sent a team to work with investigators.
“Pratt & Whitney is actively working with operators and regulators to support the inspection range of the Pratt & Whitney PW4000 engines powered by Boeing 777 aircraft,” the company said, citing the NTSB for more information. “Pratt & Whitney will continue to work to ensure the safe operation of the fleet.”