Leeham News and Analysis
There's more to real news than a news release.
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.
Airbus’ A350-1000 or Boeing’s 777-8? Part 1
Subscription required
By Bjorn Fehrm
May 9, 2024, © Leeham News: We are doing an article series comparing the capabilities of the Airbus A350-1000 and the Boeing 777X series. We started with the 777-9, the larger model. Now, we continue with the shorter 777-8, an aircraft closer in size to the A350-1000.
The 777-8 was originally launched in a shorter version together with the 777-9. Then, it went very quiet around the 777-8, with some analysts speculating that the passenger version would not be done. The 777X freighter, the 777-8F, was launched in January 2022. It became a bit longer than the 777-8. This now forms the final definition of the 777-8.
Summary:
- The comparison of the A350-1000 and the 777-8 is comparing the longer-narrower versus the shorter-wider.
- Which is the best? We use Leeham’s Aircraft Performance and Cost Model (APCM) to find out.
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.
Airbus’ A350-1000 or Boeing’s 777-9?
Subscription required
By Bjorn Fehrm
April 4, 2024, © Leeham News: Korean Air confirmed an order for 33 Airbus A350 in the week, 27 of which are the larger A350-1000. The order is significant on two accounts:
First, 27 A350-1000 and only 6 A350-900, where analysts have for years asked why the -1000 isn’t selling.
Secondly, for a carrier that has a rather 50-50 fleet of Airbus and Boeing planes, its large widebody was the Boeing 777-300ER, whereof it has 27 out of 37 Boeing 777 in total. Korean Air now chooses the A350-1000 to replace the 777-300ER. Why not the 777-9?
Was this a question of availability (the 777-9 should have been delivered in 2020 but has had several delays; the present plan says 2025), or was there a technical-economic reason for Korean Air’s decision? We examine the characteristics of the two planes to find the answers.
Summary:
- The Boeing 777-300ER was an exceptionally successful stretch of the original 777-200. The 777-9 is the sequel to the 777-300ER.
- The market did not like the original A350-1000. Therefore, the present -1000 is a reconfigured aircraft compared to the original variant.
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.
Bjorn’s Corner: New aircraft technologies. Part 50. Wrap up.
By Bjorn Fehrm
March 15, 2024, ©. Leeham News: We started the series a year ago about the New Aircraft Technologies that can be used when replacing our present single-aisle airliners.
We have covered a lot, including the typical development phases, from initial studies to preparing for the aircraft’s in-service phase.
Let’s make a resume of what we have discussed.
Figure 1. Boeing’s Truss Braced Wing X-66A demonstrator based on the MD-90. Source: Boeing.
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.
Bjorn’ s Corner: New aircraft technologies. Part 48. Maintenance Program for the A320/A321
By Bjorn Fehrm
March 1, 2024, ©. Leeham News: We are discussing 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 the modern MSG-3 maintenance program for an airliner last week, why it was created, and its main analysis principles.
Now we look at maintenance data designed to the MSG-3 standard, the Maintenance Planning Document (MPD) for the Airbus A318/A319/A320/A321.
Figure 1. The front page of the A318/A319/A320/A321 MPD no 45. Source: Airbus.