Bjorn’s Corner: New engine development. Part 5. Turbofan design problems

By Bjorn Fehrm

April 26, 2024, ©. Leeham News: We do an article series about engine development. The aim is to understand why engine development now dominates new airliner development when it comes to the needed calendar time and risks.

To understand why engine development has become a challenging task, we need to understand engine fundamentals and the technologies used for these fundamentals.

We discussed geared versus direct-drive turbofans last week. Now, we’ll examine some design problems for these engines.

Figure 1. The Pratt & Whitney PW1100G geared turbofan, with its unique aluminum fan. Source: Pratt & Whitney.

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Bjorn’s Corner: New engine development. Part 3. Propulsive efficiency

By Bjorn Fehrm

April 12, 2024, ©. Leeham News: We have started an article series about engine development. The aim is to understand why engine development now dominates the new airliner development calendar time and the risks involved.

To understand why engine development has become a challenging task, we need to understand engine fundamentals and the technologies used for these fundamentals. We started last week with thrust generation, now we develop this to propulsive efficiency.

Figure 1. The base engine in our propulsive efficiency discussion, the CFM56-7 for the Boeing 737ng. Source: CFM.

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Bjorn’ s Corner: New aircraft technologies. Part 49. Engine Maintenance

By Bjorn Fehrm

March 8, 2024, ©. Leeham News: We are discussing the different phases of a new airliner program. After covering the Design and Production, we now look at the Operational phase of a new airliner family.

For the operational phase, the airplane must pass scrutiny for Continued Airworthiness. The biggest item in a regulator’s Instructions for Continued Airworthiness is the required Maintenance program to keep an airliner airworthy. We discussed airframe maintenance in the last article. Now, we look at engine maintenance.

Figure 1. The CFM56-7 engine for the Boeing 737NG. Source: CFM.

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2024 Outlook: A Mixed Bag for Propulsion OEMs

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By Chris Sloan and Gordon Smith

January 11, 2033, © Leeham News: In 2023, a slew of problems plagued propulsion providers, with Pratt & Whitney’s GTF Engine and supply-chain shortcomings grabbing the bulk of negative headlines and customer complaints. There were bright spots for all the big three with a slew of significant orders, emerging technologies, and critical management shifts.

As the calendar turns to 2024, all eyes will be on a return to fulfilling enormous backlogs, supporting OEM production rate increases, and returning GTF-propelled planes to the skies – while edging towards new technologies, both incremental and revolutionary.

Summary
  • Pratt and its operators navigate massive AOGs (aircraft on ground) and unhappy customer claims for its GTF.
  • The GTF Advantage closes in on EIS.
  • GTF maladies open the door to a possible new platform, the long-mooted Airbus A220-500.
  • The X66A Tranonic-Truss-Braced Wing offers promise for both Pratt’s GTF and GE’s future RISE engines.
  • GEnx and GE-9X win blockbuster campaigns on the 787 and 777X as the 777X hurtles toward certification.
  • CFM’s LEAP goes from strength to strength on the heels of MAX orders and 737-7 and 737-10 certification and entry-into-service.
  • Fixing LEAP durability and delivery challenges.
  • Rolls-Royce Trent troubles continue to draw the ire of customers.
  • UltraFan testing moves forward in Roll’s quest to build a next-generation engine platform for the 2030s. Read more

Pontifications: “We’re sick and tired of new technologies:” Avolon CEO

By Scott Hamilton

Editor’s Note: As Airbus and Boeing consider new airplanes, their current generation aircraft are plagued with technical issues. The engines on the A320neo and 737 MAX families continue to have problems years after entry into service. The Boeing 787, which had ground-breaking technology when it was designed, has production issues. Flight testing early on revealed technical problems with the engine on the 777X, prompting the president of Emirates Airline to publicly suggest he won’t accept delivery until the engines are fully “mature.”

Aviation Week’s Check 6 podcast last week examined Boeing’s path toward a new airplane. Boeing CEO David Calhoun insists on waiting for new technology. But “new technology,” while in theory is a great idea, the phrase also scares people. LNA reported on this in March 2020. We’re reposting this article from then.


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Introduction

By Scott Hamilton

March 16, 2020, © Leeham News: “I can tell you from our perspective, we’re kind of sick and tired of new, new technology. It’s not proven to be the home run.”

This blunt assessment comes from the chief executive officer of the big aircraft lessor, Avolon.

Domhnal Slattery

Domhnal Slattery, the CEO, was giving his critique of whether Boeing should launch a new airplane once the 737 MAX crisis is over. (Update: Since this interview, Slattery retired from Avolon.)

Boeing was on a path to decide whether to launch the New Midmarket Airplane when the MAX was grounded one year ago this month.

Airbus was waiting for Boeing to move before deciding how to respond.

Summary
  • Airbus and Boeing should “stick to their knitting.”
  • Focus on incremental improvements for now.
  • 2030s to 2050s will be the next big advance in technologies.

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Pontifications: Moonshot for engines for Next Boeing Airplane may have to wait

By Scott Hamilton

Sept. 12, 2023, © Leeham News: The Next Boeing Airplane (NBA) may be a moonshot for CEO David Calhoun, but airlines will probably be reluctant to take a moonshot on the next new engine.

Service issues with the CFM LEAP and Pratt & Whitney GTF engines are driving airlines batty. The failures of the Rolls-Royce Trent 1000 years after entry-into-service (EIS) cost RR hundreds and millions of dollars and a confidence crisis that hurt future sales. LEAP engines are coming off wing well before initial forecasts. Every aircraft model using the GTF faced groundings as engine failures piled up.

Boeing sorely needs a successor to the 737, now in its 55th year and fourth iteration. Ron Epstein, the aerospace analyst for Bank of America, was biting in a Sept. 7 research note.

Flying a Boeing 737 is like driving a ‘68 Chevy Impala with a semi-modern dash.

 “We note that Boeing continues to ride on the coattails of its past glory. The original Boeing 737 prototype first flew in April 1967, entering service less than a year later in February 1968 with Lufthansa. Fifty-five years later, the 737 airframe remains in service through a multitude of derivative models, including the most recent 737 MAX,” he wrote.

“However, we note that the model was never intended to be such a blockbuster long-term solution. Instead, the 737 was expected to be a band-aid for the Boeing portfolio to compete with the market share-winning DC-9. The Boeing fleet lacked a smaller narrowbody model to complement the company’s larger jets, like the 707. In the spirit of the General Motors model, the 737 was intended to be the ‘cheap Chevy’ of the portfolio. Fledgling carriers would operate the cheaper model before upgrading to Boeing’s large, higher-end products like the 707 and, later, the 747, which one could see as the ‘Cadillacs’ of the portfolio.

“In our view, while the longevity of the 737 is impressive, the aircraft is now a bit of an anachronism. Operating the aircraft is like driving around in a 1968 Chevy Impala with a semi-modern dashboard. It is important to note that the 737 is the only currently manufactured commercial aircraft without fly-by-wire controls, which are a staple in modern aircraft control system design.”

Epstein worked for Boeing from 1995 to 1999 as an Applied Research Scientist. He’s a technical advisor to United Airlines for the alternative energy sector.

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Bjorn’s Corner: New aircraft technologies. Part 17P. Airframe with lower induced drag

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June 16, 2023, ©. Leeham News: This is a complementary article to Part 17. Airframe with lower induced drag. It discusses in detail the simulations we have done on a Truss Braced Wing, using our Aircraft Performance and Cost model to compare it to today’s wings and alternative future concepts.

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Pontifications: “The need for radical fuel improvements will only increase over time.”

By Scott Hamilton

May 30, 2023, © Leeham News: “The need for radical fuel improvements will only increase over time.”

That’s the definitive conclusion of Arjan Hegeman, GE Aerospace’s general manager of advanced technology.

GE is working on Performance Improvement Packages (PIPs) of its current engine lineup used on Airbus and Boeing airliners. It’s also developing the GE9X, now in testing on the Boeing 777X, and concepts of a hybrid-electric and hydrogen-fueled engine.

But the big bet is on the Open Fan “RISE” (Revolutionary Innovation for Sustainable Engines). “The Open Fan technology—it’s a go,” Hegeman declared earlier this month at a press briefing in advance of the Paris Air Show next month.

CFM RISE Open Fan engine. Credit: CFM.

The Open Fan is an evolution of the Open Rotor engine tested in the 1980s. The concept shows a dramatic reduction in fuel consumption compared with the engines of the day. But the counter-rotating rotor design was very noisy. Coupled with other technical challenges and a sudden drop in fuel prices, GE (and rival Pratt & Whitney) dropped the concepts.

But research and development continued. Today, PW thinks its Geared Turbo Fan engine will suffice for the future. Rolls-Royce is also pursuing traditional engine designs. But GE believes the problems of the Open Rotor have been solved for the Open Fan.

How?

It comes down to supercomputing, said Mohamed Ali, GE Aerospace vice president of engineering.

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Pontifications: Selling engines for profit, not as loss leaders

By Scott Hamilton

May 9, 2023, © Leeham News: Last week, I provided an overarching view of the business model the engine makers used for decades to sell their engines and services to the airlines and leasing companies. Today, we discuss this in more detail and move to other issues facing engine makers as well.

Aviation Week’s MRO Americas last month was the venue for the engine panel.


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The panelists include two from the manufacturers, Becky Johnson, I’m the Director of Marketing for CFM commercial programs at GE Aerospace, and Sam Raby, who is Associate Director at Pratt & Whitney for aftermarket marketing and strategy. Two other panelists were from the MRO sector: Russ Shelton, president of GA Telesis Engine Services, and Sebastian Torhorst, Head of Sales for Energy Services for the Americas for Lufthansa Technik.

As LNA wrote last week, the business model relies on selling engines at a steep, steep discount—sometimes up to 80%, and in rare instances, the engine maker gave (as in free) engines to customers. In either case, the quid pro quo was to enter into long-term service contracts for parts and maintenance, repair and overhaul (MRO). Deeply discounted sales meant it could take 10-15 years for the engine makers to recover development costs.

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GTF’s troubled history hurting future orders

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By Scott Hamilton and Bjorn Fehrm

May 8, 2023, © Leeham News: India’s GoFirst Airlines filed for bankruptcy last week. The carrier pointed to around 29 of its 50 Pratt & Whitney Geared TurboFan-powered Airbus A320neos being grounded as the reason.

The aircraft have been grounded for months. Despite negotiations with PW and a favorable arbitration ruling, GoFirst says PW failed to provide replacement engines. As a result, GoFirst paid about $196m in lease rates for the grounded aircraft, without being able to fly them for revenue.

Lufthansa Group last week complained that a third of its Swiss Airbus A220 fleet, also powered by the GTF, are likewise grounded with technical issues. As LNA previously reported, Air Baltic, Egyptair and Air Senegal also have A220s grounded. Iraqi Airlines has some A220s that are grounded. And now there’s news that Embraer E195-E2s at KLM’s regional airline are also grounded due to GTF issues.

India’s Indigo Airlines also has a large number of A320neos grounded with GTF problems. About 11% of the nearly 3,000 A320neos in service are grounded or fly one a week, an Aviation Week analysis revealed.

PW’s reputation was already badly damaged before the GoFirst bankruptcy. However, an LNA analysis shows that forward orders for engines on the A320neo already were suffering.

Summary

  • CFM’s LEAP has a consistently larger market share, boosted by exclusivity on Boeing 737 MAX.
  • Initially PW won more orders for A321neo; CFM has overtaken in the order backlog.
  • Including A220 (exclusive GTF power) and MAX, plus neo split, CFM’s in-service market share is 66% to 34%.
  • But going forward, CFM has 60% of the backlog across all types to PW’s 19%–with 22% of the A320neo family orders undecided on engines.

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