The regional market and scope clauses

By Bjorn Fehrm

January 17, 2017, ©. Leeham Co: Union contract Scope Clauses–the provision limiting the weight, capacity or number of aircraft operated by airlines for major carriers–are unlikely to be modified any time soon, panelists at the Air Finance Journal conference in Dublin said.

The restrictive Scope Clauses are predominate in the US. These limit the ability of small airplane manufacturers to sell aircraft in the US. Most affected are Embraer, Bombardier and newcomer Mitsubishi.

Contract negotiations in December, concluded before Christmas, resulted in no changes, surprising some. This will impact planned purchases of aircraft.We sat with Bombardier’s Ross Mitchell, vice president of commercial operations, to understand why the scope clauses are so important and why they did not change. Read more

Bjorn’s Corner: Geared turbofans

By Bjorn Fehrm

January 13, 2017, ©. Leeham Co: The time has come to go through the reasons why some turbofan engines are designed with a gearbox between the fan and the low pressure shaft.

The principle design is shown in Figure 1. It’s a graphical representation of a geared turbofan from the engine analysis software GasTurb.

Figure 1. GasTurb principal representation of a geared turbofan. Source: GasTurb.

The base idea is to have the low pressure spool of the engine to run at a considerably higher RPM than the fan. Read more

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.

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Deferrals grow as airlines fight to keep bottom line

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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.

  • Deferrals of single aisle aircraft are less worrying than for wide-body aircraft
  • For wide-bodies, it depends on the program. For the Airbus A380, deferrals turns the program back into the red. For the A350, deferrals can help with delivery commitments.
  • For the Boeing 777, deferrals spells trouble, especially for the present generation.
  • The 787 is more resilient but the slow sales make the program sensitive longer term.

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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.

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2017: the year ahead

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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.

  • Wide-body sales remain weak.
  • Narrow-body backlogs and low oil prices continue to inhibit sales.
  • China, Middle East concerns emerging.
  • United Aircraft MC-21 and COMAC C919 begin flight testing.
  • Airbus A330neo, Boeing 787-10, Embraer E195-E2 and Mitsubishi Aircraft MRJ-70 roll-out and begin flight testing.
  • Airbus A321neo and Boeing 737 MAX 8 EIS.

Read more

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.

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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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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.


  • 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?

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