Leeham News and Analysis
There's more to real news than a news release.
Pontifications: Embraer, contrary to others, looks to momentum in 2017
By Scott Hamilton
Jan. 3, 2017, © Leeham Co.: Airbus, Boeing and Bombardier look toward 2017 as a bit of a punk year, as detailed in our Look Ahead for subscribers only. Not so by Embraer.
In an exclusive interview, John Slattery, the president of Embraer Commercial, said EMB will gain “momentum” this year. This is at a time where sales at the other three of the Big Four OEMs are expected to slow off an already slow 2016.
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.
The Boom SST engine problem, Part 4
By Bjorn Fehrm
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Introduction
December 15, 2016, ©. Leeham Co: In our article series around the engine for a Boom SST, we established the thrust requirements for the engines in Part 3.
To fulfill these requirements, we have now designed four different engines. Three are of the type that Boom says it is considering, an engine that is based on an existing core.
Figure 1. Boom Technologies Boom Mach 2.2 45 seat airliner. Source: Boom.
We based these around a military core with the right characteristics for a low-to-medium bypass SST engine. The fourth engine is a custom-designed straight turbojet, very similar to the engine that propelled the only operational SST, the Concorde.
We will use the reference turbojet to understand the difference to a turbofan in this application and why the selection of an engine for a SST follows different rules than for a normal airliner.
Summary:
- Supersonic flight requires engines with low frontal areas and low mass flows.
- Should the engine be designed as for a normal airliner, the inlet drag would be prohibitive.
- The engine also must have a low pressure ratio core; otherwise the energy of the fuel is wasted on non-productive work.
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
The Boom SST engine problem, Part 3
By Bjorn Fehrm
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Introduction
December 08, 2016, ©. Leeham Co: Boom Technology and Virgin Atlantic plan to offer supersonic business class passenger traffic over the Atlantic. We covered the type of challenges that this poses in previous articles. The most difficult challenge is finding a suitable engine.
Figure 1. Boom Technologies Boom Mach 2.2 airliner with 45 seater. Source: Boom.
We described what type of engine will be required in Part 2 of the series. We will now investigate what thrust this engine must deliver at different parts of the flight envelope.
How “draggy” is supersonic flight? Why did Concorde and the Tu-144 need afterburners for the acceleration to cruise speed?
Summary:
- Supersonic drag forces slender aircraft designs to minimize supersonic drag.
- An SST needs to use a special climb technique to hold this and other drag factors low.
- Passing the sound barrier and supersonic climb is demanding flight phases
- Can a non-afterburning turbofan operate efficiently to master these phases and combat the supersonic drag?
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?
The Boom SST engine problem
By Bjorn Fehrm
Subscription required
Introduction
November 28, 2016, ©. Leeham Co: We covered Boom Technology’s and Virgin Atlantic’s plans to offer supersonic business class passenger traffic over the Atlantic in recent articles. In the first article, we focused on the problem areas that Boom technology must master.
The most difficult area is to find a suitable engine for the aircraft. Engines for long-range supersonic flight are quite different animals than the normal subsonic airliner engine. We will go through why the engines are different and give an example of how such an engine could look.
Figure 1. Boom Technologies Boom Mach 2.2 airliner with 45 seaters. Source: Boom.
By creating a concrete example of an SST engine for an aircraft the class of the Boom SST, it will be possible to understand if Boom’s claim that suitable cores are available holds water, and how realistic is it to make an SST engine from these.
Summary:
- An SST engine is very different from a modern engine for a long-range airliner.
- A high-performing long-range engine for a normal airliner has a high bypass and pressure ratio.
- A high-perfoming long-range SST engine for a supersonic airliner has a low bypass and pressure ratio.
- Intakes and exhausts on subsonic engine nacelles are simple.
- Intakes and exhausts on supersonic engine nacelles are not simple.
- Considering all these factors, we will design an engine system for the Boom SST to get a deeper understanding of the challenges involved.
Resurgence for ERJ-145
Note: Nov. 24 and 25 are Thanksgiving Holidays in the US. Our next post will be Monday.
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Introduction
Nov. 23, 2016, © Leeham Co.: The 50-seat regional jet market is dead.
That’s the conventional wisdom.
Well, not quite.
Embraer ERJ-145 is finding new life with regional airlines.
Piedmont Airlines, a unit of American Airlines, is adding the 50-seat Embraer ERJ-145 to its fleet. Eleven joined so far and next year the company plans to add 24 more.
CommutAir, an operator for United Airlines, is adding the same aircraft type to its fleet. Forty of them.
Why the mini-resurgence?
Low fuel prices and cheap airplanes.
Summary
- 50-seat regional jets were considered economically obsolete with high fuel prices.
- Sustain low prices provided a boost to the Embraer ERJ-145.
- Bombardier’s CRJ-200 hasn’t seen a similar resurgence.
2017: the year ahead
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Introduction
Jan. 3, 2017, © Leeham Co.: The New Year is here and it doesn’t look like a good one for commercial aerospace, if measured against previous outstanding years.
There are some troubling signs ahead, piling on to a slowdown in orders from last year that didn’t even reach a 1:1 book:bill.
This year looks to be worse than last. Airbus and Boeing will give their 2017 guidance on the earnings calls this month and next. Bombardier and Embraer earnings calls are a ways off, when each will provide its guidance.
But LNC believes the Big Two in particular will be hard pressed to hit a 1:1 book:bill this year and may even struggle to match 2016 sales.
Boeing’s year-end order tally comes Thursday. Airbus’ comes on Jan. 11.
Summary
Read more
1 Comment
Posted on January 3, 2017 by Scott Hamilton
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Airbus, Boeing, Bombardier, CFM, Comac, Embraer, GE Aviation, Irkut, Mitsubishi, Pratt & Whitney, Rolls-Royce, Sukhoi