MTU gets support from Pratt & Whitney to develop the WET engine

By Bjorn Fehrm

November 29, 2022, © Leeham News: MTU and Pratt & Whitney presented an EU Clean Sky project today where they will develop an advanced engine concept based on the Pratt & Whitney GTF. The project is called SWITCH, an acronym for Sustainable Water-Injecting Turbofan Comprising Hybrid-Electrics.

There are participants from 11 countries in the project, among them Pratt & Whitney’s sister company Collins aerospace, GKN’s Swedish part, and Airbus.

The engine, which has a mild parallel hybrid architecture, extracts more energy from the turbofan fuel by driving the core exhaust through a vaporizer, where it recovers more heat from the core exhaust, Figure 1. Water from the exhaust, extracted from the core exhaust in a condenser, is heated to steam by the vaporizer and then drives a steam turbine that co-drives the fan. The steam is finally injected into the combustor to lower emissions.

The WET cycle will gain about 10% efficiency compared to today’s GTF. The concept also has a hybrid part which is primarily used for a low-emission taxi.

Figure 1. The architecture of the SWITCH engine. Source: SWITCH.

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Bjorn’s Corner: Sustainable Air Transport. Part 47. eVTOL traffic

By Bjorn Fehrm

November 25, 2022, ©. Leeham News: We have gone through the flight principles for different eVTOLs, the critical systems such as battery systems and flight controls, their energy consumption/performance, and how green they are compared to other ways of getting to an airport.

This is all about the flying vehicle. But it’s only part of the system needed for this transport system to work and be safe. We now discuss the other bits needed.

Figure 1. The JFK, Newark, and Manhattan airspace. Click for a detailed view. Source: Foreflight.

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Bjorn’s Corner: Sustainable Air Transport. Part 46. eVTOL comparison with helicopter

By Bjorn Fehrm

November 18, 2022, ©. Leeham News: In the comments to last week’s Corner, there were requests for a comparison with a helicopter re. Sustainability (kWh/km). Here you go.

I also threw in a cost of operations discussion, as the helicopter is the present alternative to an eVTOL for city-to-airport air transports.

Figure 1. The Robinson R66 five-seat helicopter. Source: Wikipedia.

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Bjorn’s Corner: Sustainable Air Transport. Part 44P. eVTOL operating costs. The deeper discussion.

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By Bjorn Fehrm

November 4, 2022, ©. Leeham News: This is a complementary article to Part 44, eVTOL operating costs. It discusses the typical operating costs we can expect from an eVTOL when used in an air taxi operation.

Despite the operation of such transports being years off, an eVTOL has dominant cost factors that can be estimated today.

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Bjorn’s Corner: Sustainable Air Transport. Part 42. eVTOL range.

By Bjorn Fehrm.

October 21, 2022, ©. Leeham News: This is a summary of the article Part 42P, eVTOL range. It discusses the range of a typical eVTOL flying a feeder mission from a city center to an airport.

The 42P article details the energy consumption for each stage in the mission and the range we fly. We summarize the results here.

Figure 1. The Vertical Aerospace VX4 in an early rendering with similar looks to the eVTOL we discuss. Source: Vertical Aerospace.

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Bjorn’s Corner: Sustainable Air Transport. Part 42P. eVTOL mission range. The deeper discussion.

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October 21, 2022, ©. Leeham News: This is a complementary article to Part 42, eVTOL mission range. It discusses the typical maximum range we can expect from a certified eVTOL by mid-decade.

We have described the vehicle and the mission data in the three previous Corners; now, we analyze the energy consumption for the mission and discuss the range we can achieve.

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Achieving net zero carbon is a promise you can keep: P&W’s Webb

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By Scott Hamilton

Sept. 26, 2022, © Leeham News: The International Civil Aviation Organization (ICAO) is nearing the next step in support of dramatically cutting emissions by airlines and the aviation industry.

Graham Webb

“ICAO has been working for about the last three years on something called a long-term aspirational goal (L-TAG). That’s regarding a study that was conducted by a number of their scientists to determine if it is feasible for the aviation industry to reduce its carbon emissions specifically, to achieve a net zero standard. That’s what for a long-term aspirational goal is,” said Graham Webb, Chief Sustainability Officer for Pratt & Whitney. “At this point, the study has been completed and has been reviewed by 93 member states. It would appear that the initial motion of the language that is going to be put forward will pass.”

ICAO previously adopted the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). L-TAG is the next step, Webb said in an interview this month with LNA.

“Once that is in place, it will enable ICAO, much as it already is done with CORSIA, to establish policies that would then be enforced by all its member states in a common, in a related way as opposed to the concern that many people have had, where you would see a patchwork. You would see some countries, such as the United States, providing incentives through vendors’ tax credits. You would see Europe in the form of mandates and taxes. They have this Emissions Trading Scheme that they’ve been putting forward and running through the Parliament. The overall objective is to have this singular global aviation industry, regulatory body, ICAO, that would then set the guidelines for the industry.”

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Bjorn’s Corner: Sustainable Air Transport. Part 36. Battery Management.

By Bjorn Fehrm

September 9, 2022, ©. Leeham News: Over the last weeks, we have discussed the cells that make up the battery system for an eVTOL.

The battery system has 10,000 cells or more. All these must, on an individual level, be managed to ensure they operate inside their allowed values. The Battery Management System, BMS, has this responsibility. It’s one of the most critical safety systems in an eVTOL.

Figure 1. The Battery Management System and battery packs from EP Systems. Source: EP Systems.

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Bjorn’s Corner: Sustainable Air Transport. Part 33P. eVTOL batteries. The deeper discussion.

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August 19, 2022, ©. Leeham News: This is a complementary article to Part 33, eVTOL batteries. It discusses the trickiest system on an eVTOL, the battery system.

While Lithium Ion batteries have come a long way since the electric flight ideas took off in 2015, the battery system is still the biggest challenge for eVTOL designers, not only for total energy content but for a range of parameters.

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Bjorn’s Corner: Sustainable Air Transport. Part 33. eVTOL batteries.

August 19, 2022, ©. Leeham News: This is a summary of article Part 33P, eVTOL batteries. This article discusses the trickiest system on an eVTOL, the battery system.

The battery system supplies the energy to the VTOL, and given today’s and tomorrow’s battery technology; it’s a tight resource that needs a lot of pampering.

Figure 1. We use graphs in the Pipistrel spare parts catalog to show the battery system of the Pipistrel Velis Electro. Source: Pipistrel and Leeham Co.

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