ENGINE FAILURES MAY SIGNAL BROADER PROBLEMS

ENGINE FAILURES MAY SIGNAL BROADER PROBLEMS

In spite of a laudable safety record, recent airframe and engine incidents have together raised concern about whether we might be taking the vast improvements in safety over the last two decades for granted. Certainly, the series of high profile engine failures have caught the attention of many. What’s going on and what can be done to address these mishaps?

About the time the CFM 56 engine experienced its uncontained engine failure on Southwest 1380, killing a passenger in the direct line of fire of the rocketing engine parts, the industry was already in the thick of a series of engine failures.

These incidents culminated in twin incidents on February 20. United Flight 328, a 26-year-old 777 powered by Pratt & Whitney 4000 engines experienced an engine failure during taking off from Denver, cascading engine parts across the landscape. The same day, a PW4000 powered 747-400 cargoliner, operated by Longtail Aviation, experienced a mid-air explosion and fire on a PW4000 engine, similarly raining parts over its flight path.

These two incidents and several both before and after Southwest 1380 raise concerns about maintenance and even design and manufacturing and whether our laudable safety record on crashes is in jeopardy.

The Big Picture

We know most things went right during these events. Like those before them, the United crew, who oddly remain unnamed despite the wide-spread coverage, were able to safely land the aircraft. In its March 5 incident update, NTSB reported the spar valve, which stops fuel flow to the engine worked. But examination of the engine accessories showed multiple broken fuel, oil, and hydraulic lines and the gearbox was fractured, all feeding the dramatic fire caught in passenger images.

“It must be pointed out the aircraft landed safely,” The Giles Group’s Carol Giles, shown below, told Aerospace Tech Review. “The good news is the reliability and piloting skills that come into play, mitigates what could have been a huge catastrophe.”

Carol Giles
Carol Giles

Unprecedented Safety

At a time when the industry has delivered unprecedented safety, one is right to ask what might be going on. While crashes have occurred overseas and remain achingly few and far between, we do have numerous airframe and engine incidents that, together, raise concern and begs the question whether we are taking the vast improvements in safety over the last two decades for granted.

Certainly, the series of engine failures have caught the attention of Congress.

“Two senior U.S. lawmakers said the FAA has failed to turn over a report to Congress on airline engine safety required under a 2018 law,” reported Assurance Ltd. “Without the report it was impossible for anyone ‘to know whether the best practices and recommendations to improve airline engine safety could have helped to prevent the engine mishaps that have taken place since the October 2019 safety review.’ Recommendations to improve airline engine safety have been languishing for well over a year. Even more concerning is the potential missed opportunity to address similar airline engine safety issues before they occurred again.”

Adam Pilarski, Avitas senior vice president, shown right, thinks the problem is more systemic than just isolated incidents affecting airframes and engines.

Adam Pilarski
Adam Pilarski

“It’s not just the 737 Max,” he told Aerospace Tech Review. “Every manufacturer has problems. Every single one and I think they tried to do too much too soon because of demand. We tried to go too fast into large production. The manufacturers, unfortunately, didn’t get their stuff together before producing record numbers of engines or aircraft. Their only approach was to ask how they can squeeze out another few cents through minor tweaks not how to produce the vast numbers of engines needed. We saw similar problems with the OEMs both Boeing and Airbus.”

Pilarski noted engine issues are not unique to Pratt having affected CFM, GE and Rolls Royce.

“The problem is,” Pilarski added, “manufacturing is not sexy. Manufacturers only wanted to push out more products rather than focus on the boring stuff.

“This has been happening for years and is not new,” he continued. “They were looking at market demand rather than thinking of how to produce thousands of units. I think they didn’t focus on how you actually put it together – the boring things. They didn’t make the right effort.”

He also questions whether manufacturer emphasis on aftermarket service came at the expense of production capabilities. He has previously noted manufacturers don’t make money on engines but make it up in aftermarket service programs.

“I don’t know if the current issues are systemic from design all the way through to manufacturing,” Giles added. “It’s hard to think that every manufacturer would have a systemic issue. But it’s good to question whether or not we are going too fast.”

Leadership Test

Pilarski sees these problems as a test for the new leadership.

“We don’t know how the new leaders at these companies will address these issues,” he said, noting Pratt is now under Raytheon after its merger with UTC. “John Slattery, who I respect and admire as much as I did David Joyce, is now heading up GE. He’s a brilliant marketing guy but his strength is not in the boring development and delivery of engines. But using baseball language, he has a good bench.”

He also sees how Covid could benefit the industry. “To some degree the disaster we have now with Covid gives manufacturers breathing room since no one is pushing for new aircraft immediately,” he pointed out. “Now is a good time to do the boring stuff, figure out what went wrong with design and actually delivering one unit after another in the thousands.”

Giles also agrees Covid is an opportunity to examine what is happening with new engines and the engine/airframe combination.

“We should be asking ourselves these questions,” she concluded, noting United 328 prompted internal company discussions whether it was about bad maintenance or, perhaps, a design issue.

“You don’t know until you do the investigation,” she told Aerospace Tech Review. “I’m not sure what the root cause is of the engine events, but they are major.”

Perhaps the point is that whether the company is run by marketing, bean counters or engineers, it can still go astray as the industry has already seen.

Serious Issues

While the 737 Max may be the latest poster child, there have been serious issues with aircraft design and production with every new aircraft and, in the past 20 years, few have been delivered on time owing in part to development and production problems.

Even after delivery some, like the 787, have been grounded because of battery fires. Similarly, Pratt’s Geared TurboFan, powering the A320new, A220 and Embraer E190 has struggled through the engine problems. The question is whether what we are seeing is normal teething or a systemic problem.

Of course, there is Air Force and 787 quality issues and now the electrical system problems on 106 737 MAXs built in 2019 that is now complicating the MAX’s return to service.

Problems with Rolls Royce’s Trent 1000 prompted a redesign of the turbine blades and replacement owing to premature wear, disrupting global 787 operations. In mid 2020, EASA issued an airworthiness directive prompted by another issue, unrelated to the Trent’s previous problems. It called for one-time, ultra-high sensitivity fluorescent penetrant inspection of seal fins and replacement of parts if cracks are identified. It prompted the company to revise its inspection regime on the low-pressure turbine and focused on the disc seal fins. Rubbing wear between discs and interstage static seals could prompt cracks in the front seal fins and lead to disc cracks in the low-pressure turbine discs.

Problems have also occurred on GEnx-powered 787s after an inflight failure in 2016. The GEnx-1B-PIP2 engine suffered substantial damage when ice on the fan blades broke loose, causing the FAA to order engines replaced or repaired because it feared failure of both engines in flight.

The list goes on.

New SMS Requirements

All this is happening against a backdrop of international requirements for manufacturers to implement the Safety Management Systems (SMS) that have been widely adopted throughout the industry and is considered a significant contributor to improving safety.

SMS is a decision-making system based on proactively identifying, assessing and controlling hazards and safety risks before they result in accidents and incidents, and analyzing performance data for continuous improvement, according to the Aerospace Industries Association, involved in developing voluntary SMS standards.

Work within the industry has been ongoing since the first decade of the century culminating in the adoption of ICAO Annex 19 requiring SMS development for design and production approval holders. The FAA embraced this effort, reporting in 2018 on its Manufacturers SMS (MSMS) Pilot Project and the Part 21/SMS Aviation Rulemaking Committee (ARC), as part of an effort to develop a rulemaking package. The Notice of Proposed Rule Making (NPRM) was tabled in 2018.

Simultaneously, however, the manufacturing industry developed a standard for voluntary SMS programs known as National Aerospace Standard (NAS 9927) or Safety Management Systems and Practices for Design and Manufacturing. NAS 9927 was approved by the FAA, which encouraged industry to implement the voluntary program.

The publication of the international industry standard developed by the world’s leading aerospace designers, manufacturers and maintenance organizations, promises improved safety performance and enhanced safety culture.

Implementing a Safety Management System for Design, Manufacturing and Maintenance Providers is available free.

The team that spent two years developing the standard and included the AeroSpace and Defense Association of Europe (ASD), Aerospace Industries Association of America (AIA), Aerospace Industries Association of Brazil (AIAB), the Aerospace Industries Association of Canada (AIAC) and the General Aviation Manufacturers Association (GAMA). It enables the global aviation industry to implement a SMS consistent with the International Civil Aviation Organization’s (ICAO) Annex 19. The organizations continue their work to ensure future revisions are effective.

“Development of an internationally-recognized SMS Standard that is consistent with Annex 19 means that we now have a tool to implement key safety measures in a consistent manner up and down our industry, which ultimately results in a more accountable safety system,” said David Silver, AIA’s vice president for civil aviation at the time.

“SMS for manufacturing is coming down the pike very fast,” Giles indicated. “MROs have implemented SMS because regulators around the world are requiring it.”

United Flight 328, a 26-year-old 777 powered by Pratt & Whitney 4000 engines experienced an engine failure during taking off from Denver in February 2021. The crew was able to safely land the aircraft. Engine issues aren’t unique to one manufacturer as CFM, GE and Rolls Royce have experienced safety events as well. NTSB mage.
United Flight 328, a 26-year-old 777 powered by Pratt & Whitney 4000 engines experienced an engine failure during taking off from Denver in February 2021. The crew was able to safely land the aircraft. Engine issues aren’t unique to one manufacturer as CFM, GE and Rolls Royce have experienced safety events as well. NTSB mage.

Finding Root Causes

But SMS is a pro-active solution while other programs dig to find the root cause of problems and, according to Pilarksi, that may be what is needed.

In the late 1990s, the FAA developed a safety system requiring airlines to identify problems and follow them back to the root cause which could be as simple as the wrong tools or inadequate training. This system then requires corrections ensure the issue does not arise again. It is like a safety investigation designed to prevent the crash, not determine what went wrong and why after the fact.

Trends

There seem to be four trends colliding. The first, as Pilarski noted, the rush to meet demand. Second, are industry efforts to reduce maintenance costs by increasing time between overhauls and inspections.

Pilarski has noted in the past that it is harder to predict component lifecycles and repair costs with new designs and materials.

The question is whether the intervals between those maintenance events are really what they should be.

The infamous issues with the Rolls Royce Trent engine powering the 787 prompted the company to reduce the time between servicing as did the two United and one JAL incidents.

After a previous engine failure caused by a fractured fan blade on a United Honolulu-bound flight in 2018, United’s inspections for the 777 were set at 6500 cycles but United 328 had flown only 3000 cycles. Pratt then reduced it to 1000 cycles before the FAA mandated immediate inspections which grounded the aircraft.

After the Honolulu incident the National Transportation Safety Board cited insufficient training for Thermal Acoustic Image (TAI) inspections developed by Pratt & Whitney. It said maintenance technicians misdiagnosed a problem with the blade. In response Pratt created a more formal inspection training curriculum after which the FAA issued an AD requiring stepped up inspections.

Assurance Ltd. Director Andy Evans explained TAI causes movement between each side contacting any inclusion in the metal, creating heat by friction which is then detected by a thermal sensor.

Evans said TAI is rare in the MRO industry which relies more heavily on conventional ultrasonics which, like sonar develops an acoustic reflection for internal defect detection.

Fuselage damage resulting from the shedding of pieces of the engine from United Flight 328 is shown above. NTSB image.
Fuselage damage resulting from the shedding of pieces of the engine from United Flight 328 is shown above. NTSB image.
Nacelles are supposed to contain engine failures but clearly do not, says Adam Pilarski, Avitas senior vice president. NTSB image.
Nacelles are supposed to contain engine failures but clearly do not, says Adam Pilarski, Avitas senior vice president. NTSB image.

“It’s a current MRO issue,” Evans told Aerospace Tech Review. “The concern from the 2018 NTSB investigation is there were shockingly big flaws in the PW process in the early days.

Hopefully, inspections have been much more tightly controlled in recent years, but the JAL event suggests the FAA airworthiness directive compliance times may have been too generous.”

Evans found it surprising that the NTSB investigation on the 2018 incident yielded no recommendations. “It again — like Sioux City did a generation earlier — highlights the critical nature of NDI in engine overhaul shops, the importance of properly specifying the technique, ensuring competent inspectors, considering the human factors and ensuring the process is quality assured.”

Last July, Assurance published an analysis of NDI process failures in United’s Honolulu incident shortly after NTSB published is report identifying a low-cycle fatigue fracture. The engine had been overhauled by Pratt’s Overhaul and Repair facility in 2015. Blades received a fluorescent penetrant inspection as well as TAI, developed by Pratt in 2005 to inspect interior surfaces of the hollow core fan blade, according to the NTSB.

Interestingly, the 2015 and earlier 2010 TAI inspections revealed a thermal indication in the same location as the low-cycle fracture. This was attributed to flaking paint which affected about 25% of blades, said the board.

The report further noted that Pratt identified TAI as a new and emerging technology meaning it didn’t have to develop a formal initial and recurrent training program, certify TAI inspectors or have Level 3 inspector on staff in conformance with normal NDI practice. Despite the time between development of TAI and the 2018 engine failure, the inspection process was still categorized as new and emerging despite being used on over 9000 blades.

While the manufacturer had developed formal training on TAI the two inspectors working on the engine were not permitted to attend in favor of clearing out a backlog of blades in the shop.

“So,” said the Assurance report, “clearing the backlog appears to have been more important than formal training on the inspection. It also noted the backlog resulted in overtime begging questions about personnel fatigue. One inspector complained the procedures were ‘written for the lab rather than the shops and had lots of gaps.’”

The board also noted environmental problems in the inspection room that was bathed in sunlight that could throw off the TAI scanners. The Assurance report also questioned the frequency of FAA visits to the inspection facility.

After post-incident inspection revealed the thermal indications at the location of the fatigue crack, Pratt initiated an “over-inspection of all digital images of the TAI’s accomplished on the PW4000 112-inch fan blades according to the NTSB findings. That prompted the AD requiring an initial and recurring TAI inspections of the hollow core blades.

Preliminary findings from the scanning electron microscope (SEM) examination identified multiple fatigue fracture origins on the interior surface of a cavity within the blade. Efforts to further characterize the fracture surface, including identifying the primary origin, are ongoing says the NTSB. NTSB image.
Preliminary findings from the scanning electron microscope (SEM) examination identified multiple fatigue fracture origins on the interior surface of a cavity within the blade. Efforts to further characterize the fracture surface, including identifying the primary origin, are ongoing says the NTSB. NTSB image.

Nacelle Failure

Another issue focuses on nacelles that are supposed to contain engine failures but clearly do not and may have fallen victim to the tweaks Pilarski spoke about.

Manufacturers and FAA have been struggling with this issue for years. They are trying to develop more robust designs beyond protecting against fan blade break up and expanding to protect against disintegration of disks such as happened to an Engine Alliance powered Airbus 380 over Greenland in 2017.

Boeing is also working on solutions for when fan blades fly forward, according to FAA, which said the work relates to the 737 and will result in mandating a design change.

Evan expects a modification to make the nose cowling attachment more robust to emerge as an AD. He also noted the aircraft in service are dwindling with the retirement announcement of JAL’s 777 fleet recently. Even so, United expects to return its 777s to the fleet “in the near future,” according to statements on its earnings call.

The numerous engine incidents also begs questions about the generosity of ETOPs operations. However, it is early days yet to suggest changes will come especially with 40 years of ETOPS operational experience in the industry.

Given the issues running through both engines and airframes, it may well be time to pause and take stock to ensure advancements made in the last two decades in materials and design are not somehow becoming counterproductive to safety.

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