Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- China bans Boeing, US parts imports in tariff war April 15, 2025
- Boeing welcomes COMAC competition as Asia-Pacific demand soars April 15, 2025
- How good is the C929? April 14, 2025
- Bjorn’s Corner: Air Transport’s route to 2050. Part 17. April 11, 2025
- Uncertainty plagues airline, aerospace, lessor industries over tariffs April 10, 2025
Bjorn’s Corner: New engine development. Part 18. Combustors.
By Bjorn Fehrm
August 2, 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 covered the problem areas of (Figure 1) compression in the compressor and combustion, with its requirements on low Soot and NOx emissions. Now we look at how combustors are designed to achieve such low emissions.
Figure 1. The gas turbine cycle and its parts. Source: Rolls-Royce: The Jet Engine.
Bjorn’s Corner: New engine development. Part 16. Compressor air use.
By Bjorn Fehrm
July 19, 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 covered the problem areas of a compressor and how these achieve power-to-air-pressure conversion efficiencies of over 90% by using advanced 3D airflow modeling. Now, we look at the users of the air from the engin’s compressor.
Figure 1. The gas turbine cycle and its parts. Source: Rolls-Royce: The Jet Engine.
To what extent can the A321XLR replace the Boeing 757, Part 3
Subscription required
By Bjorn Fehrm
July 11, 2024, © Leeham News: We are comparing the Airbus a321XLR to the Boeing 757 to understand to what extent it can replace the 757 on the longer routes it operates for major airlines like United, American, and Delta.
We have looked at the development and operational history of the aircraft, their Apples-to-Apples capacity and range. Now, we use Leeham’s Aircraft Performance and Cost Model (APCM) to compare the operational costs of the aircraft.
Summary:
- The Boeing 757-200 has the same passenger capacity as the A321LR/XLR and a larger cargo capacity.
- Its range can compete with the A321LR but not the XLR. Both beat the 757 on operational economics.
Bjorn’s Corner: New engine development. Part 13. The compressor.
By Bjorn Fehrm
June 28, 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 covered the need for the axial speed of the core air to decrease and increase depending on the needs of the core engine’s sections. Now, we will start to look at the different parts of the core in more detail. We start with the compressor.
Figure 1. The gas turbine cycle and its parts. Source: Rolls-Royce: The Jet Engine.
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 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: 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.
Re-engining the Boeing 767, Part 2
Subscription required
By Bjorn Fehrm
December 14, 2023, © Leeham News: We are 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 FAA, EASA, and other regulators for production and delivery beyond 2027.
We have described the history of the 767 and the key data of the different variants in last week’s article. Now, we look at what airframe modifications are necessary to house more efficient engines and what consequences these bring.
Summary:
- New, more environmentally friendly engines for the 767 mean changes to the landing gear and structures to house larger and heavier engines.
- For the payload capacity to stay the same a deeper grab in the 767-400 toolbox is necessary than just adopting the landing gear.
Pontifications: Airbus ponders A330neo MRTT, Boeing ponders KC-46A re-engine
By Scott Hamilton
By Scott Hamilton
Nov. 28, 2023, © Leeham News: In a reversal of intent, the airplane that Airbus may submit to the US Air Force for the next round of aerial tanker procurement may be based on the A330neo instead of the current production A330-200ceo MRTT.
The Air Force, however, may forego competition between Airbus and Boeing and place a sole-source follow-on order with Boeing for the KC-46A tanker, based on the 767-200ER. Boeing already has a contract for 179 KC-46As, and the USAF appears to be leaning toward a sole-source award. Political pressure from Airbus partisans and others who favor competition may prevail.
Related articles
- Airbus to develop second generation MRTT based on A330neo. (Aviation Week.)
- Lockheed Martin sees MRTT as complimentary to KC-46A
- Lockheed bows out, Airbus to continue, Boeing favored in tanker procurement
Airbus wants to discontinue production of the A330-200ceo-based MRTT. The neo-based version would be based on the A330-800. Sales of the -800 are poor—fewer than 20 have been ordered. An -800 based MRTT will breathe life into the nearly still-born model.
- Boeing considers re-engining the 767-300ERF and the KC-46A.
- KC-46A, 767-200, A330 MRTT exempt from 2027 ICAO standards.