Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- How good is the COMAC C919? March 20, 2025
- Boeing CFO Brian West: OK on tariffs for now, backlogs and inventories help March 20, 2025
- Pontifications: Southwest’s core problems are not solved by business model changes-yet March 19, 2025
- Boeing 2024 Proxy Statement: Executive Compensation includes retirement gifts for Calhoun, Deal; housing support for Ortberg, Pope, and other stuff March 17, 2025
- Bjorn’s Corner: Air Transport’s route to 2050. Part 13. March 14, 2025
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
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.
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.
Bjorn’s Corner: New engine development. Part 7. Open Rotor Propulsive Efficiency
By Bjorn Fehrm
May 10, 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 started a discussion around Open Rotor engines after looking at geared versus direct-drive Turbofans. We now look deeper at the Open Rotor Propulsive Efficiency.
Figure 1. The CFM RISE Open Fan engine. Source: CFM.
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 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.
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 engine development. Part 2. Thrust generation
By Bjorn Fehrm
April 5, 2024, ©. Leeham News: We started an article series about engine development last week. The aim is to understand why engine development nowadays dominates the needed time and the risks involved in new aircraft development.
To understand why engine development has become perhaps the most challenging task, we need to understand engine fundamentals and the technologies used for these fundamentals. We start this week with thrust generation.
Figure 1. The principle for thrust generation using air as medium. Source: NASA.
Bjorn’ s Corner: Engine development. Part 1. Introduction
March 29, 2024, ©. Leeham News: We finished our article series about New Aircraft Technologies last week. It dealt with the different new technologies that a next-generation airliner could use to increase efficiency and by it environmental emissions.
An area that we touched upon but didn’t dig deeper into was engine development. When airframe development historically decided how long a new generation of aircraft took to develop, it gradually changed to engine development being the more calendar-time-consuming and riskier development for the last generations. This article series will discuss why and what can be done about it.
Figure 1. CFM RISE, a new engine development for the next generation of airliners. 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.