Leeham News and Analysis
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Leeham News and Analysis
- Bjorn’s Corner: Air Transport’s route to 2050. Part 25. June 6, 2025
- New RISE powerplant benefits from decades of GE research and development June 5, 2025
- Engine makers emphasizing durability, reliability June 4, 2025
- Boeing CEO: Lessons learned are key to certification of 737-7/10 and 777X June 2, 2025
- Digital twin is a key to JetZero’s hopes for Blended Wing Body entry June 2, 2025
Airbus sets new delivery record for 2016
By Bjorn Fehrm
January 11, 2017, ©. Leeham Co: Airbus Commercial Aircraft presented a new record in yearly deliveries at its Press Briefing in Toulouse today. The division of an integrated Airbus (therefore Airbus Commercial Aircraft, ACA) delivered 688 aircraft during 2016, thereby beating its target of 650 aircraft for the year.
Airbus A321neo with Pratt&Whitney engines was certified end 2016. Source: Airbus.
Orders were also higher than expectations at 731 net orders, giving a Book to Bill of 1.06. The market, including LNC, widely expected Airbus to fall somewhat short of a 1:1 book:bill.
There were no formal forecasts given for 2017. ACA President Fabrice Bregier stated that he expects it to be over 700 deliveries but full details will given at the Airbus Group’s financial press briefing in February.
Bjorn’s Corner: Turbofan developments in 2017
By Bjorn Fehrm
January 06, 2017, ©. Leeham Co: Before we finish of our series on airliner turbofan technology, let’s spend this Corner on what will happen on the airliner engine front during 2017.
While there is no totally new engine that comes into the market during 2017 there are a number of new variants of existing engine families that will be introduced.
Figure 1. GasTurb principal representation of a three shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
If we start with the engines for regional/single aisle aircraft and then climb the thrust scale, we will cover the engines in climbing thrust class.
Bjorn’s Corner; Turbofan engine challenges, Part 7
By Bjorn Fehrm
December 16, 2016, ©. Leeham Co: After the turbine comes the engine’s exhaust system. This is where the thrust characteristics of the engine are formed. It is also the environment that defines the back pressure for the fan and turbines. It’s therefore more high-tech than one thinks.
For the very high bypass airliner engines of tomorrow, the common fixed bypass exhaust of today (Station 18 in Figure 1) will not be acceptable. Variable exhaust areas will have to be introduced.
Figure 1. GasTurb principal representation of a three shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
On engines that function in high supersonic speed, it gets really complex. Not only is the exhaust area variable, it must have a dual variation exhaust, a so-called Con-Di nozzle.
Bjorn’s Corner; Turbofan engine challenges; Part 6
By Bjorn Fehrm
December 08, 2016, ©. Leeham Co: We have now come to the turbine in our trip through a modern turbofan. The turbines make up the rear of the engine, before the propelling nozzle.
The turbines are the workhorses in the engine. They take the energy released by the fuel in the combustion chamber and convert it to shaft hp to drive the fan or compressors.
Figure 1. GasTurb principal representation of a three-shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
The hotter they can operate, the better. They can then generate more hp on a smaller size turbine. The temperature of the gas entering the high pressure compressor is one of the key parameters of a gas turbine. It dictates the power efficiency of the core and how much work it can perform to drive the fan and the compressors. Read more
Bjorn’s Corner: Turbofan engine challenges, Part 5
By Bjorn Fehrm
December 02, 2016, ©. Leeham Co: We will now look at the combustor area in our series on modern turbofan engines. There is a lot of activity in this area, as it sets the level of pollution for the air transportation industry for some important combustion products.
We will also finish off the compressor part of our series by looking at the bleeding of cooling air for the engine and for servicing the aircraft with air conditioning and deicing air.
Figure 1. GasTurb principal representation of a three-shaft turbofan like our reference Rolls-Royce Trent XWB. Source: GasTurb.
The amount of air which is tapped from compressor stages for cooling and other purposes can exceed 20% of the core flow (some of the flow paths are shown in Figure 1). At that level, it has a marked influence on the performance of the engine. Read more
The Boom SST engine problem, Part 2
By Bjorn Fehrm
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Introduction
December 01, 2016, ©. Leeham Co: Boom Technology and Virgin Atlantic plan to offer supersonic business class passenger traffic over the Atlantic. We covered the number of challenges that this poses in recent articles. The most difficult challenge is finding a suitable engine.
We started the investigation into a suitable engine in the last article. A Supersonic Transport Aircraft (SST) needs an engine which is very different from the latest crop of high-performance airliner engines.
Figure 1. Boom Technologies Boom Mach 2.2 airliner with 45-seater. Source: Boom
The air entering the engine intake at Mach 2.2 is taken from standing still to a speed of 450m/s within a fraction of a meter. This raises the air pressure and temperature more than the combined intake/fan/low compressor does for a modern turbofan. The result is that the core’s high pressure compressor must adapt; it can’t have a high compression ratio (then things get too hot).
Add to that, that the engine must be slender. It can’t have a wide fan and therefore high by-pass ratio because the supersonic drag of such large engines would be too high.
Summary:
- The SST engine must be based on a core with a low pressure ratio.
- Such cores are no longer available in modern airliner engines.
- One must use cores from the military field of supersonic engines.
- We check what kind of engine can be constructed around such a core.
- Is the Boom SST mission then possible with an engine done with an existing core?
Bjorn’s Corner: Turbofan engine challenges, Part 4
By Bjorn Fehrm
November 18, 2016, ©. Leeham Co: In our series on modern turbofan airliner engines, we will now go deeper into the compressor part. Last week, we covered the fundamentals of compressors. As compressors and turbines use the same principles, we also covered the fundamental working principles of turbines.
We also described that compressors are temperamental parts, which can protest to wrong handling with violent “burps” (burst stalls with the combustion gases going out the front of the engine) or end up in a rotating stall where it simply stops working.
Figure 1. Stylistic cross section of a two shaft turbofan with both axial and radial compressor. Source: GasTurb.
Turbines, on the other hand, are your robust companions. Aerodynamically they just work, albeit more or less efficiently dependent on what one asks them to do (mechanically it can be very different; we recently saw a turbine disintegrate with large consequences on an American Airlines Boeing 767 in Chicago). More on the turbines later.
In the GasTurb cross section of a two shaft turbofan in Figure 1, the engine has both an axial and a radial compressor. We will consider why engine designers combine these two for certain engine types. Read more
CSeries out of London City Airport, Part 2. UPDATED 2017.01.24
By Bjorn Fehrm
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Introduction
This article, which was published on the 14 November, has been updated with new information from Bombardier. The range of the CS100 from London City airport has increased due to improved performance from the aircraft and a new engine version with more thrust, the PW1535G engine.
November 14, 2016, ©. Leeham Co: In the last article about operating the Bombardier (BBD) CS100 from London City Airport (LCY), we could see that the runway is about half the length of an international airport’s runways. This will have a significant impact on the Take Off Weight (TOW) that can be used when commencing a route from London City.
Figure 1. London City airport, housed in the docklands of London’s east end. Source: Wikipedia.
The manufacturers have data in their aircraft brochures that state that one should be able to takeoff with e.g. the CS100 at Maximum Take Off Weight (MTOW) from a runway which is 1,463m/4,800ft long. London City Airport’s runway is 1,508m/4950ft long, so then things should be fine?
No, the figures from the OEMs is the planning figure for actual runway used and London City airports usable take-off Runway is given as 3,934ft. In addition there is 394ft stopping distance available.
To understand how this can be used required a bit of information that we did not have at the time of writing the original article. Some of the information we used was not up to date and we did not use the strongest engine available (PW1535G) when analyzing if an operator could fly direct between New York from London City.
Bombardier came to our help and we have now been able to update the data with which to feed our performance model. This shows among other things that it’s possible to operate a direct connection between London City airport and New York, given that the number of passengers (the payload) is restricted to around 50 passengers or below.
We have revisited the two cases, SWISS European operations from London City and how would a direct operation London-New York work. You find the updated article below.
Summary:
- London City Airport puts special requirements on the aircraft serving it.
- It puts stringent requirement for takeoff and approach/landing.
- We use new information and our performance model to present what routes can be served with a CS100 from the London City Airport.
Deferrals grow as airlines fight to keep bottom line
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Introduction
Jan. 09, 2017, © Leeham Co.: Airlines have deferred or are thinking about deferring more than 400 airplanes in the near term, a review of decisions and deliberations that have been made during the last 12 months.
LNC tracked announcements last year of deferrals and statements by airlines that they are thinking about doing so.
We began identifying macro-level issues last week in our posts about emerging concerns for the 787 and LNC’s Outlook for 2017.
Reasons vary widely for the deferrals, these reports indicated. Low oil prices. Slowing economies. Declining financial results. Worries about two of the three top Middle Eastern carriers. A capital squeeze in China. Pressure on long-haul carriers from the emerging sector of low cost, long-haul airlines. Preserving capital expenditures to keep the bottom line in the black.
Today we detail the deferrals we tracked.
Summary
Read more
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Posted on January 9, 2017 by Scott Hamilton
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