Leeham News and Analysis
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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
The all-important cabin. Part 2
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By Bjorn Fehrm
May 30, 2024, © Leeham News: We will do an article series about the all-important cabin and its seating for an airliner. The cabin layout and its comfort are the most important part of an airliner for the passenger. For an airline it’s its face to the customer.
We will look at the different types of cabins used and how these use the airliner’s real estate, what the cost is, and what the weight is. With the weight, we can also predict how different cabins affect the aircraft’s performance.
Summary:
- The configuration of the cabin has a large influence on total seating, weight, and cost.
- The relationships change up to 500%.
Bjorn’s Corner: New engine development. Part 9. The role of the Nacelle
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 why Open-Rotor engines have two fan stages, either both rotating in different directions or one rotating followed by a de-swirling stator stage. Now we study the flow field ahead of and around the fans to understand the role of the nacelle and the open rotor spinner.
Figure 1. A graphic showing the different parts of a Pratt & Whitney PW1100G nacelle. Source: Pratt & Whitney.
Bjorn’s Corner: New engine development. Part 6. Open Rotor
By Bjorn Fehrm
May 3, 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.
We have in previous Corners discussed geared versus direct-drive turbofans. Now the time has come to discuss Open Rotor engines.
Figure 1. The GE 36 Open Rotor engine, the father to today’s CFM RISE. Source: GE Aviation.
Bjorn’s Corner: New engine development. Part 4. Propulsive efficiency
By Bjorn Fehrm
April 19, 2024, ©. Leeham News: We have started 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 for development and the risks involved.
To understand why engine development has become challenging, we need to understand engine fundamentals and the technologies used to achieve them. Last week, we discussed propulsive efficiency and learned that it depends on the Overspeed the engine gives its exhaust air-gas mix.
We then used two direct-drive engines from CFM (CFM56 for the 737 ng and LEAP for the 737 MAX) to give us examples of Overspeeds and their corresponding Propulsive efficiency. Now, we look at geared turbofans.
Figure 1. One of the first geared turbofans (if not the first), the Turbomeca Aubisque used on the SAAB 105 jet trainer. Source: Swedish Military Airplane History.
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.
Bjorn’s Corner: New aircraft technologies. Part 51. Wrap up
By Bjorn Fehrm
March 22, 2024, ©. Leeham News: Last week we did the first part of the Wrap-up of our 50 article series about the New Aircraft Technologies that can be used when replacing our present single-aisle airliners.
Now, we summarize the last 25 articles in the series, which covered how to develop, produce, and support a new airliner.
Figure 1. The Program Plan for a new airliner. Source: Leeham Co.
Quality Will Drive Pay for Spirit Executives
By Dan Catchpole
Feb. 6, 2024 © Leeham News: Quality more than quantity will drive Spirit Aerosystems executives’ compensation when the company unveils its new formula when it files its proxy statement in March, the company’s CEO Pat Shanahan told Wall Street analysts on Tuesday. 
“It will be significantly different, and the heaviest weighting will be only quality,” he said during a conference call discussing Spirit’s fourth quarter earnings report.
The panel blowout on Alaska Airlines Flight 1282 last month highlighted ongoing quality problems at Spirit and Boeing. Unlike the violent decompression on the 737 MAX 9, the quality problems typically just create financial headaches and public embarrassment for the two companies.
Spirit recorded $59M in net income, 48 cents adjusted earnings per share, and $42M free cash flow in the fourth quarter of 2023, its first profitable quarter since the beginning of 2022.
The company’s performance was boosted by a contract renegotiation and financing deal signed with Boeing in October. Spirit is getting close to signing a similar deal with Airbus, Shanahan said.
Summary
- Quality metrics for exec compensation
- Short term, long term plans for improving quality
- Negotiations with Airbus
Re-engining the Boeing 767, Part 4
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By Bjorn Fehrm
February 1, 2024, © Leeham News: We have been looking at a re-engine of the 767, a move that Boeing is considering to avoid a production stop after 2027. The present 767 engines don’t pass emission regulations introduced by the FAA, EASA, and other regulators for production and delivery beyond 2027.
We used our Aircraft Performance and Cost model to look at the economics of the original 767 Freighter versus a re-engined one before Christmas. Now, we install a passenger long-range cabin and look at the per-passenger mile economics of a re-engined 767-300ER versus the original version.
Summary:
- New, more environmentally friendly engines would give the 767-passenger version better fuel economics.
- The higher the engine maintenance costs of the new engines make the Cash Operating Costs difference between the existing 767-300ER and the new version small.
Bjorn’s Corner: New aircraft technologies. Part 41. Production learning curve
By Bjorn Fehrm
December 08, 2023, ©. Leeham News: We are discussing the different phases of an airliner development program. After covering Conceptual, Preliminary, and Detailed design, the manufacturing of prototypes, and their roles in Flight Tests, we now look at Production.
Last week, we explained why aircraft projects often fail 100 to 200 aircraft into production. What’s not well understood is the effects of production learning on product cost.
Figure 1. The development plan for a new airliner. Source: Leeham Co.