Electric aviation

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Grumble
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Electric aviation

Post by Grumble » Fri Jan 08, 2021 6:52 am

I know there have been a few posts on the Death of Fossil Fuels thread but I thought maybe electric aviation is more specialist and deserves a thread of its own.

This is only a concept, but Airbus have come up with a fuel cell pod that mounts on the wing: https://www.airbus.com/newsroom/stories ... ation.html
It contains the fuel tank as well as the engine, which is why it’s so much bigger than a normal engine that they’ve had to put the wings on top of the fuselage.

This news comes after the first certification of an electric plane late last year: https://www.easa.europa.eu/newsroom-and ... tion-fully
This one is only a light trainer aircraft, but it can fly for 90 minutes. I’m sure bigger aircraft will be in the works.

We’re still a long way from a trans-Atlantic flight, but I don’t think we’re all that far away from a paying passenger flight, I can well imagine an island hopping electric plane in the Shetlands or Hebrides.
I know this is vitriol, no solution, spleen venting, but I feel better having screamed, don’t you?

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Martin Y
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Re: Electric aviation

Post by Martin Y » Fri Jan 08, 2021 2:11 pm

Slightly off-topic but might become relevant; noise.

The 8-bladed propeller design makes me think of those A400m Atlas planes which we hear coming over our house as they fly in or out of the UK. Brize Norton is almost 50 miles away so they're not at low level, but I still notice them because they're so bl..dy loud. Last one I checked on the flightradar app was at over 24000 ft but I only looked it up because I thought the noise must have been something at unusually low level.

TBH I wonder if I'm just being oversensitive to the sound because you hear so few multi-prop planes these days, but my pitiful Googling skills are not telling me if they really are louder than similarly sized jets.

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Grumble
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Re: Electric aviation

Post by Grumble » Fri Jan 08, 2021 2:35 pm

Martin Y wrote:
Fri Jan 08, 2021 2:11 pm
Slightly off-topic but might become relevant; noise.

The 8-bladed propeller design makes me think of those A400m Atlas planes which we hear coming over our house as they fly in or out of the UK. Brize Norton is almost 50 miles away so they're not at low level, but I still notice them because they're so bl..dy loud. Last one I checked on the flightradar app was at over 24000 ft but I only looked it up because I thought the noise must have been something at unusually low level.

TBH I wonder if I'm just being oversensitive to the sound because you hear so few multi-prop planes these days, but my pitiful Googling skills are not telling me if they really are louder than similarly sized jets.
They are I think, one of the benefits of jets is that relative to the power they are quiet. The question then becomes is the noise due to the motor or the propellers - or more realistically what proportion of noise is down to those two factors.
I know this is vitriol, no solution, spleen venting, but I feel better having screamed, don’t you?

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Re: Electric aviation

Post by Gfamily » Fri Jan 08, 2021 3:01 pm

I recall being taken to the airport back in the late 60s early 70s as an aunt used to fly over from Dublin for Christmas etc. At one time she flew out on what I think was a Vickers Viscount, and I was struck by how bl..dy noisy it was (at least on the ground).

As the A400 is also powered by turboprop engines, I wonder if that is why it seems so much louder than other planes.
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Re: Electric aviation

Post by FredM » Fri Jan 08, 2021 3:24 pm

Grumble wrote:
Fri Jan 08, 2021 2:35 pm
Martin Y wrote:
Fri Jan 08, 2021 2:11 pm
Slightly off-topic but might become relevant; noise.

The 8-bladed propeller design makes me think of those A400m Atlas planes which we hear coming over our house as they fly in or out of the UK. Brize Norton is almost 50 miles away so they're not at low level, but I still notice them because they're so bl..dy loud. Last one I checked on the flightradar app was at over 24000 ft but I only looked it up because I thought the noise must have been something at unusually low level.

TBH I wonder if I'm just being oversensitive to the sound because you hear so few multi-prop planes these days, but my pitiful Googling skills are not telling me if they really are louder than similarly sized jets.
They are I think, one of the benefits of jets is that relative to the power they are quiet. The question then becomes is the noise due to the motor or the propellers - or more realistically what proportion of noise is down to those two factors.
A lot of noise also comes from the airframe, especially during descent when energy is being dumped as the plane slows. There have been proposals for low noise aircraft, notably from a consortium led by Ann Dowling, however funding to build a prototype would cost billions.

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Re: Electric aviation

Post by Sciolus » Fri Jan 08, 2021 4:20 pm

There has been a lot of talk about open-rotor engine designs for airliners, which are basically turbine-powered props. They are good for fuel efficiency and carbon emissions, but terrible for noise, so they've never got anywhere.

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Re: Electric aviation

Post by shpalman » Fri Jan 08, 2021 4:57 pm

Sciolus wrote:
Fri Jan 08, 2021 4:20 pm
There has been a lot of talk about open-rotor engine designs for airliners, which are basically turbine-powered props. They are good for fuel efficiency and carbon emissions, but terrible for noise, so they've never got anywhere.
You mean a propfan, not a turboprop?
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Re: Electric aviation

Post by shpalman » Fri Jan 08, 2021 5:01 pm

Grumble wrote:
Fri Jan 08, 2021 6:52 am
I know there have been a few posts on the Death of Fossil Fuels thread but I thought maybe electric aviation is more specialist and deserves a thread of its own.

This is only a concept, but Airbus have come up with a fuel cell pod that mounts on the wing: https://www.airbus.com/newsroom/stories ... ation.html
It contains the fuel tank as well as the engine, which is why it’s so much bigger than a normal engine that they’ve had to put the wings on top of the fuselage.
Or is that because they're propeller engines?
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Re: Electric aviation

Post by FredM » Fri Jan 08, 2021 5:04 pm

FredM wrote:
Fri Jan 08, 2021 3:24 pm
Grumble wrote:
Fri Jan 08, 2021 2:35 pm
Martin Y wrote:
Fri Jan 08, 2021 2:11 pm
Slightly off-topic but might become relevant; noise.

The 8-bladed propeller design makes me think of those A400m Atlas planes which we hear coming over our house as they fly in or out of the UK. Brize Norton is almost 50 miles away so they're not at low level, but I still notice them because they're so bl..dy loud. Last one I checked on the flightradar app was at over 24000 ft but I only looked it up because I thought the noise must have been something at unusually low level.

TBH I wonder if I'm just being oversensitive to the sound because you hear so few multi-prop planes these days, but my pitiful Googling skills are not telling me if they really are louder than similarly sized jets.
They are I think, one of the benefits of jets is that relative to the power they are quiet. The question then becomes is the noise due to the motor or the propellers - or more realistically what proportion of noise is down to those two factors.
A lot of noise also comes from the airframe, especially during descent when energy is being dumped as the plane slows. There have been proposals for low noise aircraft, notably from a consortium led by Ann Dowling, however funding to build a prototype would cost billions.
Incidentally, we regularly have to suffer Typhoons beating up the skies over Norwich in combat drills - they make a tremendous racket. The station commander once had to issue an apology when 3 were sent up instead of the usual 2 - their switchboard was flooded with complaints.

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Re: Electric aviation

Post by Matatouille » Sat Jan 09, 2021 9:57 am

shpalman wrote:
Fri Jan 08, 2021 5:01 pm
Grumble wrote:
Fri Jan 08, 2021 6:52 am
I know there have been a few posts on the Death of Fossil Fuels thread but I thought maybe electric aviation is more specialist and deserves a thread of its own.

This is only a concept, but Airbus have come up with a fuel cell pod that mounts on the wing: https://www.airbus.com/newsroom/stories ... ation.html
It contains the fuel tank as well as the engine, which is why it’s so much bigger than a normal engine that they’ve had to put the wings on top of the fuselage.
Or is that because they're propeller engines?
Yep, prop planes almost always end up with the wing on top, because props are huge. Although in this Hydrogenprop the props aren't as big as most - 6 powerplants on an airframe size that would usually have 2 big-ish turboprops or turbofans - they're clearly big enough (and perhaps the outer ones outboard enough) that the landing gear legs (v. heavy) would need to be really long to prevent propstrikes if props mounted on a low wing. An alternative would be low wing with the powerplant pod on top of the wing, but the top surface of a wing generates about 70% of the lift so they like to keep them clean.

As for noise, as a rule yes props are noisier than ducted fans or turbofans, its simply an acoustic containment thing. An exception is that turbofans are usually noisier from behind than turboprops but more modern ones have sexy aerodynamic features to make the different speed & temperature airflows mix more gradually & quietly in the exhaust. Anyone who lives near the flightpath to an airport frequented until recently by FlyBe would probably be familiar with the quietness turboprop tech can achieve, their turboprop Dash 8 Q400s are about the best there are for noise. The Q stands for Quiet. They're pretty equivalent to most jets, but at certain angles up close much noisier. Inside they're noisier than equivalent jets I thought, despite the active noise cancelling (same tech as in headphones except really big) to counter the blast of air hitting the fuselage every time a prop blade sweeps by.

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Re: Electric aviation

Post by shpalman » Sat Jan 09, 2021 10:15 am

You'll notice though that nobody is making 4-engined airliners anymore. Two big engines are preferable. If six small prop engines were preferable to two larger ones then turboprop aircraft would already have that configuration. Unless it's hard to make turboprop engines with so little power.
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Re: Electric aviation

Post by Matatouille » Sat Jan 09, 2021 11:04 am

shpalman wrote:
Sat Jan 09, 2021 10:15 am
You'll notice though that nobody is making 4-engined airliners anymore. Two big engines are preferable. If six small prop engines were preferable to two larger ones then turboprop aircraft would already have that configuration. Unless it's hard to make turboprop engines with so little power.
True, but that's more a result of jet turbine based powerplants now being highly mature and reliable, but also more efficient the bigger* you make them. With it also being cheaper to maintain 2 powerplants on an aircraft versus 3 or 4, we have this trend towards 2 engines. Today its all about your plane having the Engines Turn or Passengers Swim Extended Range Twin Operations approval (ETOPS) certificate.

That isn't to say that there aren't advantages to unlock from more distributed power. Wing structures people dream of having the powerplant loads distributed over the span more rather than just plonked as big point loads. How about if we could get away from these circular engine thrust sources entirely, and instead have something equivalently efficient that's nozzle was an extremely long strip along the entire trailing edge of a wing? Aerodynamicists may be quivering in extacy at the thought. If the physical or economic attributes of future power technologies are different to the current paradigm, the optimum aircraft shape for them will be different.



*To an extent higher thrust tends to be more efficient, but more noticably, the higher bypass ratio. The more air you have going round the side - through the propeller or bypass fan, compared to through the core - the more efficient an engine will get. Hence engines today are bigger than they used to be for equivalent thrust leading us to 737 max etc as you know well.

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Re: Electric aviation

Post by shpalman » Sat Jan 09, 2021 12:01 pm

Anyway the fuel cells in this engine which Airbus won't build will only be as electric as the hydrogen used to power the hydrogen-powered concepts they won't build, so it's hardly electric like the one engine on the E-Fan X which they cancelled (not to be confused with their E-Fan which they cancelled first).
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Re: Electric aviation

Post by bjn » Sat Jan 09, 2021 1:15 pm

Matatouille wrote:
Sat Jan 09, 2021 11:04 am
shpalman wrote:
Sat Jan 09, 2021 10:15 am
You'll notice though that nobody is making 4-engined airliners anymore. Two big engines are preferable. If six small prop engines were preferable to two larger ones then turboprop aircraft would already have that configuration. Unless it's hard to make turboprop engines with so little power.
True, but that's more a result of jet turbine based powerplants now being highly mature and reliable, but also more efficient the bigger* you make them. With it also being cheaper to maintain 2 powerplants on an aircraft versus 3 or 4, we have this trend towards 2 engines. Today its all about your plane having the Engines Turn or Passengers Swim Extended Range Twin Operations approval (ETOPS) certificate.

That isn't to say that there aren't advantages to unlock from more distributed power. Wing structures people dream of having the powerplant loads distributed over the span more rather than just plonked as big point loads. How about if we could get away from these circular engine thrust sources entirely, and instead have something equivalently efficient that's nozzle was an extremely long strip along the entire trailing edge of a wing? Aerodynamicists may be quivering in extacy at the thought. If the physical or economic attributes of future power technologies are different to the current paradigm, the optimum aircraft shape for them will be different.



*To an extent higher thrust tends to be more efficient, but more noticably, the higher bypass ratio. The more air you have going round the side - through the propeller or bypass fan, compared to through the core - the more efficient an engine will get. Hence engines today are bigger than they used to be for equivalent thrust leading us to 737 max etc as you know well.
MIT have been playing with an ionic propulsion system that does just that. They have a working on scale model. No idea about the efficiency and how well it scales up.

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Re: Electric aviation

Post by shpalman » Sat Jan 09, 2021 1:45 pm

bjn wrote:
Sat Jan 09, 2021 1:15 pm
Matatouille wrote:
Sat Jan 09, 2021 11:04 am
shpalman wrote:
Sat Jan 09, 2021 10:15 am
You'll notice though that nobody is making 4-engined airliners anymore. Two big engines are preferable. If six small prop engines were preferable to two larger ones then turboprop aircraft would already have that configuration. Unless it's hard to make turboprop engines with so little power.
True, but that's more a result of jet turbine based powerplants now being highly mature and reliable, but also more efficient the bigger* you make them. With it also being cheaper to maintain 2 powerplants on an aircraft versus 3 or 4, we have this trend towards 2 engines. Today its all about your plane having the Engines Turn or Passengers Swim Extended Range Twin Operations approval (ETOPS) certificate.

That isn't to say that there aren't advantages to unlock from more distributed power. Wing structures people dream of having the powerplant loads distributed over the span more rather than just plonked as big point loads. How about if we could get away from these circular engine thrust sources entirely, and instead have something equivalently efficient that's nozzle was an extremely long strip along the entire trailing edge of a wing? Aerodynamicists may be quivering in extacy at the thought. If the physical or economic attributes of future power technologies are different to the current paradigm, the optimum aircraft shape for them will be different.



*To an extent higher thrust tends to be more efficient, but more noticably, the higher bypass ratio. The more air you have going round the side - through the propeller or bypass fan, compared to through the core - the more efficient an engine will get. Hence engines today are bigger than they used to be for equivalent thrust leading us to 737 max etc as you know well.
MIT have been playing with an ionic propulsion system that does just that. They have a working on scale model. No idea about the efficiency and how well it scales up.
No idea if they've got any further with their flying clothes rack in the past two years either, although the team did reckon that microwave plasma thruster thing was bogus too.
molto tricky

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