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
Bjorn’s Corner: Sustainable Air Transport. Part 16. Thrust generation
April 22, 2022, ©. Leeham News: Last week, we examined propulsion system alternatives and their principal advantages and disadvantages. Now we go deeper into these alternatives.
All propulsion systems for aircraft use a propulsion device like a propeller or a fan to generate forward thrust. We use this article to understand how these work and their characteristics before we go into how we create the shaft power to drive them.
Figure 1. The propulsive efficiency as a function of speed for different thrust generating concepts. Source: Aircraft propellers, is there a future? MPDI document.
Bjorn’s Corner: Sustainable Air Transport. Part 15. Hydrogen propulsion system choices.
By Bjorn Fehrm
April 15, 2022, ©. Leeham News: Last week, we examined different airliner types’ power requirements and the importance of their size classes in the market.
Now we look at what propulsion system alternatives are available when using hydrogen as the energy source and their principal advantages and disadvantages.
Figure 1. CO2 emission by airliner segments. Source: EU Hydrogen-powered aviation report.
Bjorn’s Corner: Sustainable Air Transport. Part 14. Propulsion system requirements.
By Bjorn Fehrm
April 8, 2022, ©. Leeham News: Last week, we discussed the architecture of a liquid hydrogen fuel system. We now start looking at the propulsion system of a hydrogen aircraft.
Before discussing how a propulsion system is done, we must understand what power requirements different airliner types have and the importance of these types in the market.
Figure 1. The World Jet market forecast for the next 20 years. Source: JADC.
Bjorn’s Corner: Sustainable Air Transport. Part 13. Hydrogen fuel system and APU.
By Bjorn Fehrm
April 1, 2022, ©. Leeham News: Last week, we looked at how to store hydrogen in an aircraft. We could see the gaseous storage of hydrogen is too heavy other than for demo systems and extreme short-haul. For practical airliners, liquid hydrogen is the solution.
Now we look at what this means for the aircraft fuel system and how to configure a suitable Auxiliary Power Unit, APU.
Figure 1. Typical placement of hydrogen tanks. Source: Leeham Co.
Bjorn’s Corner: Sustainable Air Transport. Part 12. Hydrogen storage.
By Bjorn Fehrm
March 25, 2022, ©. Leeham News: Last week, we looked at the energy density by mass and volume for hydrogen and regular Jet fuel (Kerosene), Figure 1.
With this information, we now look at how these fuels can be stored in an aircraft.
Figure 1. The Volume and Mass densities of fuels. Source: Boeing.
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Bjorn’s Corner: Sustainable Air Transport. Part 11. Hydrogen and SAF.
By Bjorn Fehrm
March 18, 2022, ©. Leeham News: In our series, we have now seen the major limitations batteries as an energy source impose on an airliner and that hybrids work but don’t bring any advantages for an airliner.
The alternatives are to use an energy source with a higher energy density and combine it with an efficient propulsion system. Sustainable Aviation Fuel, SAF, has the same high energy density as today’s Jet fuel and hydrogen’s density is three times higher than Jet fuel.
Figure 1. The Volume and Mass densities of fuels. Source: Boeing.
Bjorn’s Corner: Sustainable Air Transport. Part 10. Where Hybrids work.
By Bjorn Fehrm
March 11, 2022, ©. Leeham News: After our articles about Serial Hybrids and Parallel Hybrids showed they were unsuitable for airliners, where do these make sense?
The obvious answer is for our stop-and-go cars (as we then can recover the brake waste energy). Still, there are aeronautical special cases where hybrids can bring advantages. Let’s look into these.
Figure 1. The variable angle of rotor blades. Source: FAA Helicopter Flying Handbook.
Bjorn’s Corner: Sustainable Air Transport. Part 9. Parallel Hybrids.
March 4, 2022, ©. Leeham News: This is a summary of the article Part 9P. Parallel Hybrid, the Deeper Discussion.
We look into the Pratt & Whitney, Collins Aerospace, and De Havilland project to create a Parallel Hybrid propulsion alternative for the Dash 8 turboprops.
The project “targets a 30% reduction in fuel burn and CO2 emissions, compared to a modern regional turboprop airliner” according to the Pratt & Whitney press release.
Figure 1. The Parallel Hybrid components of the project. Source: Pratt & Whitney video.
Bjorn’s Corner: Sustainable Air Transport. Part 9P. Parallel Hybrid. The deeper discussion.
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By Bjorn Fehrm
March 4, 2022, ©. Leeham News: This is a complementary article to Part 9. Parallel Hybrid. It uses Leeham Company’s Aircraft Performance Model from our consultancy practice to analyze the design of a Parallel Hybrid aircraft for regional operations.
Our design brief is to make turboprop upgrade packages for De Havilland DH8-200,-300, and-400 aircraft. By using a Parallel Hybrid we could “target a 30% reduction in fuel burn and CO2 emissions, compared to a modern regional turboprop airliner” according to Pratt & Whitney Canada. Time to check if we can reach these levels.
Bjorn’s Corner: Sustainable Air Transport. Part 8. Serial Hybrids.
February 25, 2022, ©. Leeham News: This is a summary of the article Part 8P. Serial Hybrid, the deeper discussion.
We take an ES-19 type of battery aircraft and add a range extender to avoid the inadequate range we found in Part 6 and 6P.
Initially, it seems a good idea. We can use the benefits of the battery and then complement it with energy from the range extender. As you systematically work through the concept, the problems surface.
Figure 1. Serial Hybrid works for cars (Toyota Prius pictured), but not for aircraft. Picture: Toyota.