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.

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Bjorn’s Corner: Sustainable Air Transport. Part 6. Energy consumption.

By Bjorn Fehrm

February 11, 2022, ©. Leeham News: In a sister article, Part 6P. Energy consumption, the deeper discussion we use Leeham’s Aircraft Performance Model from our consulting practice to generate the aeronautical energy consumption for aircraft like Eviation’s Alice and Heart Aerospace’s ES-19.

This is the energy needed to combat the drag of the airframe during flight (Figure 1). We then add the losses in the chosen propulsion system to arrive at the energy drawn from the energy source.


Figure 1. Simplified force model for an aircraft. Source; Leeham Co.

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Forecast 2022: Sustainability

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By Bjorn Fehrm


February 7, 2022, © Leeham News: The year that passed was when Sustainability broke through the walls of “I’m not convinced we have a problem” and “If so, what shall we do about it.”

The declarations ahead of, at, and after COP26 in Glasgow, United Nations 26’th climate conference, had many major states and organizations commit to targets for the reduction of Greenhouse gases by 2030 and 2050.

With this change in mind and traction, what can we expect to see in 2022 from the Air Transport industry?

Idea for Sustainable Air Transport, a hydrogen regional. Source: Sustainable Aero Lab.

  • The years that passed were run-up years. Now the preparations shall lead to the first results.
  • We summarize what we can expect to see during 2022.

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Boeing invests $450m in Wisk Aero air taxi venture

By Bjorn Fehrm

January 25, 2022, ©. Leeham News: Boeing and Wisk Aero yesterday had a media briefing on why Boeing is extending its investment in Wisk Aero with a further $450m.

The main technology is not the eVTOL aircraft. Wisk is just one of many upstarts that relies on batteries and multiple electrical propulsors to create a VTOL air taxi. It’s the pilotless operation that’s the key technology in the project. As perhaps the only VTOL company, Wisk goes directly to pilotless flight.

Brian Yutko, VP of Sustainability and Future Mobility at Boeing, explained: “The pilotless flight technology is of great interest to Boeing. It’s challenging technology, but it has a wide field of applications once mastered. We are not targeting our airliners but other civil and military applications. It’s an important driver for us in the continued support for our Wisk joint venture.”

Figure 1. The fifth-generation prototype Cora, with which flight tests are done in New Zeeland. Source: Wisk Aero.

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Bjorn’s Corner: Sustainable Air Transport. Part 3. Low hanging fruit.

By Bjorn Fehrm

January 21, 2021, ©. Leeham News: Whatever is done in terms of new Sustainable technology for the aircraft, will have a limited influence on the amount of Greenhouse gases that Air Transport emits before 2050.

We will only get the new aircraft types into operation about 15 years before the deadline and with, on average, 100 to 200 aircraft per year. That’s 1,500 to 3,000 of the total of 25,000 aircraft that operate in our skies daily. It will not reduce our Greenhouse gas emissions significantly.

Sustainable Aviation Fuel, SAF, will help, but only when it’s available in quantity and to a reasonable cost. We can do things that have a much faster effect, and that’s how we manage our flights.

Figure 1. The US flights as seen on Flightradar24 yesterday. Source: Flightradar24.

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Reducing one’s carbon footprint through flying choices

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By Vincent Valery


Jan. 20, 2022, © Leeham News: Discussions about reducing commercial aviation’s carbon emissions have become more prominent over the last few years.

Many projects claim that electric(-hybrid) and hydrogen aircraft will be available in the not-too-distant future to make net-zero emissions flying a reality. Sustainable Aviation Fuels (SAFs) will also drastically reduce lifecycle carbon emissions with only minor changes to the current aircraft.

The IATA committed to a net-zero carbon emissions target by 2050. While all those long-term aspirations are well, significant challenges remain.

LNA has highlighted that the low energy density of batteries means that electric aircraft can at best work on small planes for short flights. Developing a medium-haul hydrogen-powered aircraft will require numerous innovations that suggest an entry into service before 2035 is not realistic. The challenges in increasing SAFs supply affordably to meaningful levels are monumental.

We have pointed out that all the above are far into the future. To meaningfully reduce emissions over the next decade, the introduction of more fuel-efficient gas turbines and turboprops is the only realistic and impactful lever.

Another lever has not been mentioned so far to reduce one’s carbon emissions. Other than not flying at all, how we fly from A to B can have significantly different carbon footprint levels.

This series will highlight the different levels of carbon emissions depending on how one flies on different routes.

  • Setting the problem out;
  • Challenges in defining unit emissions;
  • Factors outside one’s control;
  • Introducing a few examples.

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Bjorn’s Corner: Sustainable Air Transport. Part 2. The problem to solve?

By Bjorn Fehrm

January 14, 2021, ©. Leeham News: Before we dig into the different alternatives we have for more Sustainable Air Transport, let’s look at the problem and its sources.

Figure 1 shows the emissions of CO2 per person since 1900 and the rise of the world temperature. The increase in world temperature changes the weather, with increased weather-related emergencies in recent years.

Figure 1. The increase in CO2 emission per capita and the rise of the world temperature from 1900 to 2018. Source: Wikipedia.

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Bjorn’s Corner: Sustainable Air Transport. Part 1. A deeper look.

By Bjorn Fehrm

January 7, 2022, ©. Leeham News: We finished a 34 article series before Christmas about the enormous work involved to get a new aircraft certified for passenger transport.

It was a background article series to the one we start now, a deeper series on what’s involved in designing air transport vehicles that are less polluting for our environment. We have seen a landslide of such projects in the last years, and from an experienced aircraft designer’s desk, most of these are doomed for failure.

Figure 1. The Embraer Energia concept aircraft. A credible Sustainable Air Transport research program. Source: Embraer.

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Pontifications: Bringing some reality on electric airplanes

Nov. 15, 2021, © Leeham News: The momentum and press about electric airplanes is spinning out of control.

By Scott Hamilton

Earlier this month, there was an article from one of the most respected news organizations by a reporter who apparently isn’t an aviation reporter that read like a press release from a start-up company. The normal beat reporter would never have been taken in by the hype.

The start-up claims there will be a battery-powered BAe 146 by 2027 with a 460-mile range. Aviation reporter Jason Rabinowitz had a field day on Twitter with the claim.

LNA’s Bjorn Fehrm wrote a long series about the technical challenges of battery-powered electric airplanes. Let’s now look at the market implications.  Read more

Bjorn’s Corner: The challenges of airliner development. Part 12. The Prelaunch Phase.

By Bjorn Fehrm, Henry Tam, and Andrew Telesca.

July 16, 2021, ©. Leeham News: Last week, we showed the first cut of an overall Program Plan for our 19 seat airliner project.

Now we discuss the Prelaunch Phase activities in more detail, including what type of knowledge, tools and resources we need to get on board for the project.

Figure 1. The Viking Twin-Otter utility-oriented unpressurized 19 seater. Source: Wikipedia.

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