Electric and Hydrogen aeroplanes - feasibility and issues

ATR has been selected by the EU's Clean Aviation Joint Undertaking to lead the future of low-emission regional flight

The aims is to be the first to fly a hybrid-electric regional aircraft by 2030.

https://www.atr-aircraft.com/pressp...zNjA3NzYkbzEkZzAkdDE3NTgzNjA3NzYkajYwJGwwJGgw
As part of Clean Aviation’s Ultra-Efficient Regional Aircraft (UERA) thrust, ATR will spearhead two ambitious development projects aimed at demonstrating the integration of hybrid-electric propulsion, advanced propeller systems and electrified aircraft systems on a regional aircraft.

By 2030, ATR will achieve a world first: flying a hybrid-electric regional aircraft using an ATR 72-600 test bed. This breakthrough will be made possible through several projects, two of which will be led by ATR, with the support of the European Union, and in collaboration with international industry and research organisations, including Safran and RTX businesses Collins Aerospace and Pratt & Whitney Canada.

ATR’s flagship project, HERACLES, (Hybrid-Electric Regional Aircraft Concept for Low EmissionS), will define an ultra-efficient regional aircraft concept integrating hybrid-electric propulsion, high-performance batteries, and a thermal engine compatible with 100% Sustainable Aviation Fuel. These technologies will be flight-tested through DEMETRA (Demonstrator of an Electrified Modern Efficient Transport Regional Aircraft), using an ATR 72-600 flying test bed.
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I'm still not sure about hybrid-electric aircraft, at least not a low number of propellers.

You end up with an ~80% efficient transmission.
 
Scott Kenny said:
I'm still not sure about hybrid-electric aircraft, at least not a low number of propellers.

You end up with an ~80% efficient transmission.
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Exactly, for conventional planes it doesn't make sense, exept maybe for a mini hybrid. If you have a starter generator anyway, you could as well use it to boost the take off power a little bit. Supercaps could be used for this purpose without adding much additional weight.

However I do see the point in replacing the complicate gear system of the V-22 Osprey with an electric system. A tilt wing with fixed nacels and electric driven propellers (could be with three electric engines in a row, for safety) would be a much simpler and more reliable system.
 
Nicknick said:
Exactly, for conventional planes it doesn't make sense, exept maybe for a mini hybrid. If you have a starter generator anyway, you could as well use it to boost the take off power a little bit. Supercaps could be used for this purpose without adding much additional weight.

However I do see the point in replacing the complicate gear system of the V-22 Osprey with an electric system. A tilt wing with fixed nacels and electric driven propellers (could be with three electric engines in a row, for safety) would be a much simpler and more reliable system.
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I meant like 4+ props.
 
Scott Kenny said:
I meant like 4+ props.
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One project that i've been following is Era from AURA AERO
https://aura-aero.com/en/era/
First flight 2027
19 seats
19,000 lb (8.6 tonnes) of MTOW
1900 kW of power on 8 engines
250 kn Cruise speed
250FL Flight ceiling
250 NM Typical length of a flight

Their "orderbook" has apparently already reached 700+ planes, or around 10 Billion $, as announced at PAS2025.

They have recieved backing by the French state and the EU
--> https://cinea.ec.europa.eu/news-eve...aviation-funding-paris-air-show-2025-06-20_en

https://twitter.com/x/status/1935972189561668044
View: https://x.com/aero_aura/status/1935972189561668044


They are also planning to set-up a manufacturing facility in Florida.
--> https://www.flgov.com/eog/news/pres...vernor-ron-desantis-highlights-new-air-france
AURA AERO also announced plans for a major second phase: construction of a 500,000-square-foot manufacturing facility at Daytona Beach International Airport to produce its next-generation 19-seat hybrid-electric aircraft, ERA. This expansion is expected to create more than 1,000 jobs and further position Florida at the forefront of aviation innovation.
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https://twitter.com/x/status/1935269646124359723
View: https://x.com/aero_aura/status/1935269646124359723
 
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The Aura Aero propulsion layout is definitely the future of short haul airline travel. I'll explain.

500nm battery only range is already possible today. The problem is with standard flight planning rules require extra range to allow emergency diversion to a second airport and 15 minutes of loiter. This means that 500nm battery range would only be ~250-300nm usable.

This is where the jet fueled range extending generator comes into play. It would allow the aircraft to fly the full 500nm entirely on battery only. The range extender doesn't need to run on a normal flight but it covers the emergency diversion requirements. The range extender only needs to be sized to provide enough electricity for a low speed cruise. The Aura Aero is generators are about 25% of the power rating of max power. As the design has 8 electric props on the wings the two generators most likely use two of same motors in power generation mode.

The second advantage of the generators is the fuel capacity can be increased to allow the range to go up above 1,000nm. The generators can run the entire flight which reduces the rate of the battery depletion. Again the generators don't need to be sized to provide enough electricity for maximum cruise speed. On a 1,000nm flight the aircraft then had a 50% fuel saving from the battery.

A third advantage to the generators is when landing at an airport that has no charging infrastructure. They can leave the generators running for a couple hours on the ground and charge the batteries up before the return flight. It will allow this propulsion layout to cover maybe 80% of the flights. More than 80% of the world's flights are under 1,000nm.

All of the designs will need to have a long/ straight wing and have a 250-300 knot cruising speed to have any chance of success. Just like how cars now have structural battery packs in the floor the obvious solution is to have a structural battery pack in the wing. This keeps the fuselage light and reduces the wing bending moment.

Flying across the Pacific or Atlantic jet fuel will still be used in 50 years time. Hydrogen can not work.
 
Flying across the Pacific or Atlantic jet fuel will still be used in 50 years time. Hydrogen can not work.
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Yep, only SAF can be an alternative today, with all its caveats obviously. My favorite "green airliner" concepts replaces kerosene with ammonia, but with only half the energy contains range takes a huge hit. Albeit we have 19 000 km range airliners nowadays, I wonder what their range would be with NH3 fuel. Still acceptable ?
In order to recover some energy lost in the shift from kerosene to NH3, the late REL of Skylon fame had had a bright idea: crack some NH3 into LH2, somewhere between the ammonia tanks and the turbofans. That LH2 will literally energize the mix thrown into the turbofan. In pasing this would leverage some of the money and engineering wasted into all those "pure LH2 airliner" studies.
 
Ammonia cracking (or Methanol/Methane).is nothing completly new. I made a research project which ended up with 5 to 7 % incresed efficincy with Methane/Biogas.The piston and compression ratio was unchanged from a MAN gas engine and the cylinder head was slightly modified to prevent backfire. Note, no.one would liquify the H2/N2/NH3 after cracking. Fully cracking is impossible, the amount of heatvrequired is too high. In piston engines, you can use the cooling heat for gasification of the Ammonia which would really help.
 
GTX said:
View: https://www.youtube.com/watch?v=fEudbAjschs


https://www.heartaerospace.com/news...t-flight-of-world-s-largest-electric-aircraft
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Hopefully electrification at this scale will make strides. I thought they had gone hybrid power as an intermediate step but this was all electric - again or still?

Some initial thoughts: The cockpit looks incredibly spartan, even for a maiden flight. The undercarriage seems on the small side for an aircraft of this class (especially as batteries alter landing dynamics). The propellers are small as well, interested to know how all electrics' rpms and other qualities compare to turboprops'.

It may just be my impression but Heart Aerospace has been, let's say very keen, to produce notable steps. This flight fits in with that pattern, while I do also recognize this as an achievement in its own right. I also wish they'd stayed within the EU, but it is what it is.
 
I believe that the final design will be hybrid-electric to provide more flexibility in range and payload. The company has stated that this is basically a demonstrator aircraft, not a production conforming version, so that may explain the spartan interior and smaller landing gear. I remember an article in Aviation Week that stated that the design evolved after they started building the prototype, but rather than make costly and time consuming changes, they decided to finish it according to the original specs and incorporate all the design changes into the second test aircraft. One of the biggest changes the second prototype will incorporate is a design alteration to eliminate the wing struts.
 
Sooner or later they will find out that the battery capacity is not sufficient, we should already know the story (Elice, Lilium....). It might end up as hybrid plane or it will be postponed into the far future when the wonder batteries will be available...
 
New website —> https://www.aura-aero.com/en/era
What is the status of the ERA program?
Testing of the first prototype is expected to begin by the end of 2026, leading to a maiden flight in 2027 and market launch before 2030.

What propulsion technology makes it possible for ERA to fly 1,500 km?
Powered by 8 electric motors (ENGINeUS, developed by Safran and the world’s first certified electric aircraft engine) and 2 turbo-generators compatible with SAF, ERA will switch between hybrid and electric modes according to flight needs, offering a range of 900 NM (1,500 km).
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https://www.linkedin.com/posts/safr...ogenerators-activity-7487492577160593408-GvxW
Safran Helicopter Engines and AURA AERO have reached a new milestone in their partnership regarding the hybrid electric propulsion system of the ERA (Electric Regional Aircraft), the future 19-seater regional aircraft. The two companies have signed an agreement covering the development and integration of Safran turbogenerators for the ERA prototype, paving the way for the series production of its propulsion system. This agreement follows on from a memorandum of understanding in 2023 and represents a key milestone towards the aircraft’s maiden flight, certification and future entry into service.

The ERA’s propulsion architecture will consist of eight electric propulsion units powered by two TG600 turbogenerators, each capable of supplying 600 kW of electricity. These turbogenerators are based on Safran Helicopter Engines’ latest-generation Arrano engine and two GENeUS electric generators supplied by Safran Electrical & Power, which will also supply the ENGINeUS motors for the electric propulsion units. This architecture has been designed to combine reliability, operational performance and low consumption, whilst meeting the requirements of commercial operation and series production.
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https://fr.linkedin.com/posts/aura-aero_auraaero-activity-7485027283297107970-l6jT
ERA's industrialization reaches a new milestone.
Designing a new aircraft is one challenge. Building the industrial capabilities to produce hundreds of them is another.
Today, AURA AERO and Piper Industrial Manufacturing Company (PIMCO), the specialized manufacturing division of Piper Aircraft, announced a strategic partnership to accelerate the industrialization of ERA, our 19-seat hybrid-electric regional aircraft.
By combining nearly 90 years of aerospace manufacturing expertise with our vision for decarbonized regional aviation, we are strengthening the industrial foundation that will enable ERA to move from development to high-rate production.
With nearly 700 aircraft already on order and entry into service planned from 2030, we continue to build the industrial ecosystem that will bring the next generation of regional aviation to life.
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