Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- Bjorn’s Corner: Air Transport’s route to 2050. Part 19. April 25, 2025
- How good is the C929? Part 2. April 24, 2025
- Boeing First Quarter Results Update: China is 10% of the backlog, with 500 in “Unidentified” April 24, 2025
- Boeing First Quarter Results: Tariffs, Return flights, $10.55bn asset sale April 23, 2025
- RTX Q1 2025 Earnings: GTF Talk Takes A Back Seat To Tariffs April 22, 2025
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
Subscription required.
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.
Bjorn’s Corner: Turbofan engine challenges, Part 3
By Bjorn Fehrm
November 12, 2016, ©. Leeham Co: In our trip through a modern turbofan airliner engine and its technologies, we looked last week at the engine intake and the fan. We now continue with the compressor parts.
As compressors and turbines use the same principles (but in opposing ways), we will look at these principles this week and how their roles in the engine create their special characteristics.
Figure 1. Stylistic cross section of a three-shaft turbofan with section numbers. Source: GasTurb.
As before, to make things concrete, we use a GasTurb simulation of a Rolls-Royce Trent XWB 84k engine to look at practical data when needed. As before, I have no specific knowledge about the engine and will not use any data outside what is public information.
The GasTurb cross section of a three-shaft turbofan is shown in Figure 1. We will examine the sections between station numbers (22) and (3) and (4) and (5) in the general discussion of compressors and turbines. We will then look at some data for common compressors. Read more
Clouds overhang Bombardier ahead of earnings call
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Introduction
Nov. 9, 2016, © Leeham Co.: Bombardier reports its 3Q2016 and nine month earnings Thursday and as the year prepares to enter its last 45 days, disappointment 
hangs over the company and the stock.
Summary
- Despite winning firm orders for the CSeries from Air Canada and Delta Air Lines early in the year, no other new orders have been announced.
- Deliveries of the CSeries will only be about half those projected, due to engine delivery delays from Pratt & Whitney.
- The $1bn investment from the federal Canadian government hasn’t been achieved, but an announcement may come as early as next week that an agreement has been reached.
- Boeing revised the design of the 737-7 to sit “right on top of” the CS300.
- Embraer (Brazil) is taking the government bailout of CSeries to the World Trade Organization (WTO) in inquiries, with the USA lending support.
Flying the CSeries
By Bjorn Fehrm
November 09, 2016, ©. Leeham Co: After my preparations at Bombardier (BBD) in Montreal, it was time to take an early flight to BBD’s test center in Wichita (KS) the next day. We spent the afternoon in briefings and went flying Wednesday.
Figure 1. FTV8 (CS300) and FTV2 (CS100) at BBD test center. Source: Leeham Co.
The trip to Wichita was with American Airlines regional carrier American Eagle on a BBD CRJ200. Within two days, I would experience the first and smallest regional jet, the CRJ200 (albeit in coach) and Bombardier’s latest and largest jet, CS300, which encroaches on the turf of the single aisles as a direct competitor to the Airbus A319 and Boeing 737-700/7.
At the test center, just off the runway to Wichita International, I would be joined by Mike Gerzanics, who was test flying for FlightGlobal. We last met when we test flew the Airbus A350 in Toulouse in Spring 2015. Read more
Bjorn’s corner; Turbofan engine challenges; Part 2
By Bjorn Fehrm
November 04, 2016, ©. Leeham Co: We will now start to go through a modern turbofan airliner engine and look at the technologies which are used and what are their technical challenges. We will start today with the engine intake and the fan.
To make things concrete, we will use a GasTurb simulation of a Rolls-Royce Trent XWB 84k engine. This will provide us with realistic example data for the different parts of the engine. I want to stress that all values are assumed as typical for such an engine. I have no specific knowledge of the Trent XWB and will not use any data outside what is public information.
Figure 1. Stilistic cross section of a three-shaft turbofan with section numbers. Source: GasTurb.
The GasTurb cross section of a three-shaft turbofan is shown in Figure 1. We will use the station numbers in the figure to navigate the engine and the data from the simulation to understand modern airline engines and their typical data. Read more
Preparing to fly the CSeries
By Bjorn Fehrm
November 03, 2016, ©. Leeham Co: We were invited to Bombardier (BBD) in Montreal last week for a series of special events.
The visit had three purposes: attend the roll out of airBaltic’s CS300 (reported here), prepare to fly the CSeries in the simulator and finally to test fly the aircraft at BBD’s Wichita (KS) test flight facility.
Figure 1. Training to fly the CSeries at the Mirabel based Simulator. Source: Leeham Co.
It was mid-October when the chance came to test fly the CSeries. The ideal time would be October 24-26, just before the test aircraft, FTV8 (the CS300 route proving aircraft), would take off for the Airshow China in Zhuhai.
The testing would have three parts:
- Study the aircraft via BBD’s online training program.
- Fly the aircraft in the CSeries simulator in Mirabel, close to Montreal.
- Fly FTV8 from BBD’s test flight station in Wichita (KS).