Bjorn’s Corner: New engine development. Part 10. Propeller, Rotor or Fan?

By Bjorn Fehrm

June 7, 2024, ©. Leeham News: We do an article series about engine development. The aim is to understand why engine development now has longer timelines than airframe development and carries larger risks of product maturity problems.

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

Following the last Corner on airframe integration, several comments were made about the definition of propeller, open rotor, and/or fan. So, we’ll explore this further.

Figure 1. Evolution of Wright Brothers propellers from 1903 to 1905. Source: wright-brothers.org

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Bjorn’s Corner: New engine development. Part 10. Airframe integration

By Bjorn Fehrm

May 24, 2024, ©. Leeham News: We do an article series about engine development. The aim is to understand why engine development now has longer timelines than airframe development and carries larger risks of product maturity problems.

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

In the last Corner, we looked at the nacelles used for a turbofan engine and for an open-rotor engine. Now, we go one step further and look at the integration of modern engines on an airliner.

Figure 1. Boeing 737NG (left) and MAX (right) nacelles compared. Source: Leeham Graphic from Boeing 737 images.

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Bjorn’s Corner: New engine development. Part 8. Open Rotor technology

By Bjorn Fehrm

May 17, 2024, ©. Leeham News: We do an article series about engine development. The aim is to understand why engine development now has longer timelines than airframe development and carries larger risks of product maturity problems.

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

In the last Corner, we looked at why Open-Rotor engines are more efficient. Their propulsive efficiency can be considerably higher than that of a turbofan. We will explore this further this week.

Figure 1. A counterrotating Open Rotor design that SAFRAN ground tested in 2019. Source: SAFRAN.

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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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