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Brystar45
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Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 6:55 am

Howdy everybody my name is Bryant I am sorry I haven't been active on here but anyways I wanted to explain something a little more clearly, please forgive me if its a bit long just a fascinating topic to think about here.

What I wanted to say is that while yes the Quad Jets and Tri Jets are not in the skies as much anymore but with Alternative fuels and new technologies they will be back but differently, Since Jet engines use fuel (Kerosene) to power the engines well there has been a rise of Alternative fuels such as Hydrogen, Battery, Electric Aircrafts in recent years, such an exciting time in Aerospace!

For example Airbus has announced plans for a Hydrogen Aircraft that they will be releasing in 2035, and its between a Blended Wing Body, Turbofan and a Turboprop Aircrafts. Since Hydrogen is a new concept for Aircrafts then I do see Quad Jets and Tri-Jets returning but powered Hydrogen instead of Kerosene.

I am still waiting for Boeing to announce their Hydrogen Concept Aircraft but I believe it will be after the whole Fiasco that happened with them.

So people saying that Quad Jets like the A380 and the B747 yes there time is nearing the end but the B747 will live alot longer because of her capacity capabilities as a freighter.

Another return of Tri-Jets will be with the Supersonic Airliners, such as Boom Supersonic's Overture and Aerion Supersonic, So if anyone says Tri-Jets are gone, they are mistaken plus Supersonic Jets are making a comeback and the FAA just approved a rule with Supersonic Jets making it much more possible for them, Also FAA licensed Space Florida for the Shuttle Landing Facility as well, such exciting times!

What I am trying to get at is that in the beginning Hydrogen and Electric powered Aircrafts are going to need more than two engines to get them airborne, then a traditional Jet engine will be and its going to be excited to see these new power sources be in the next coming decades.

I don't just love Aviation but I love Railways too, In the UK there was a study from Network Rail recently which by 2050 the entire UK Railway network will be Net-Zero Carbon which trains will either be powered by Overhead Electrification (OLE), Battery and Hydrogen Powered Trains, which its exciting and I am glad the UK is thinking forward of alternative powered fuels and Electrification of their Railways, I always favor those since it brings great benefits to the environment and get more ridership too. The plan is the Decarbonization plan for 2050 with Network Rail its rather interesting and I am excited what the future will hold for the UK!

Also good news I am finally going to be taking my FAA Training for my Flight Dispatcher License and it will be at the Local College that I finally graduated had my ceremony on December 2020. So I am happy that my future is going to start and eventually I can land into the FAA/ NASA and keep on going for my Masters in Aeronautics with Embry-Riddle and when this mess subsides be able to travel again, My Journey to the FAA/ NASA and be more involved with this amazing and awesome industry, I can't wait to leave Retail behind and go for my career in Aeronautics! My future is just beginning, my ticket to my future!

Also what is everybody's thoughts of Alternative fuels on Aircrafts, Battery, Hydrogen and so forth, very exciting times!
Going for my goals of being in the Aerospace Industry, Traveling the world and more!
 
GalaxyFlyer
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 3:04 pm

Keep dreaming in H2, lots of reasons planes won’t be powered by it. Yes, gravimetrically very energy dense, but very light, so needs huge storage volumes. Very hard to contain in any vessel, very hard on the materials, both storage and engines. Not say anything about the energy needed to separate it from H2O.

https://energypost.eu/hydrogen-fuel-cel ... ll-expert/
 
mxaxai
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 4:58 pm

GalaxyFlyer wrote:
https://energypost.eu/hydrogen-fuel-cell-cars-competitive-hydrogen-fuel-cell-expert/


You cannot fill up like you do with gasoline or diesel. It is actually pretty ridiculous how hard it is to fill up a HFC powered car
You won’t even go 100 miles on current tech hydrogen tanks that are still safe to carry around in a car
Fuel cells wear out crazy fast and are hard to regenerate
Hydrogen as a fuel is incredibly hard to make and distribute with acceptably low losses

That's just factually wrong, though losses are indeed higher than for battery powered vehicles. Compare for example https://pubs.rsc.org/en/content/article ... ivAbstract
The Toyota Mirai has a range >300 miles, with >500 miles planned on the next version.
Hydrogen stations exist and are about as easy to operate as regular gas stations or current electrical systems.
Current automobile fuel cells have a projected lifespan of approx. 6,000h, similar to ICE or batteries.


Now, I fundamentally agree that batteries are a better form of renewable energy storage for cars.

But there are some applications where hydrogen makes sense. The largest problem is that it requires completely new infrastructure for the expected volumes. For large & long-range applications, for example trains, trucks, ships and stationary industrial systems, hydrogen starts to become advantageus compared to batteries (and gasoline). This is partially because hydrogen benefits from upscaling more than batteries, and partially because those applications can avoid the logistical issues that come with hydrogen distribution.

Many companies that traditionally relied on ICE are investing heavily into industrial hydrogen systems, for example Shell, Volvo, Daimler & Iveco: https://www.shell.com/energy-and-innova ... scale.html

On aircraft, neither hydrogen nor batteries can be a 1-for-1 replacement for the current propulsion systems. Yet, unless batteries make huge leaps in the next 10-20 years, future aircraft with a meaningful range and payload will have to be powered by either hydrogen or kerosene.
 
Brystar45
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 6:32 pm

This is a very fascinating topic since Hydrogen Aircrafts are making a headline in recent years.

I brought this up because this isn't for the present but for the future, and while yes right now its very difficult but remember thats how it was in the older days as well when Jet turbine aircraft needed more than two engines to power up, but as technology got better, better materials and tools came along the requirement of four engine aircrafts diminished to just three and two, and ETOPS it became possible for two engine aircrafts to fly longer with less risk of failure, but with Hydrogen Aircrafts and so forth we may see four engine and three engine aircrafts become much more possible. Plus they will be designed a bit differently than current Aircraft types.

Thats why there is an old saying "What is old is new again." Because I see in the Aerospace circles of people saying that Quad Jets are dead and all that but in reality I see it like this, yes Quad Jets have mostly been replaced but I think its traditional Jet fuels what about with Alternative fuels I think there are going to come back because of what I said in the last paragraph.
Going for my goals of being in the Aerospace Industry, Traveling the world and more!
 
Okie
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 8:28 pm

Brystar45 wrote:
This is a very fascinating topic since Hydrogen Aircrafts are making a headline in recent years.


Hydrogen is a massive polluter when used in an infernal combustion engine.
The problem is excess Oxygen with Hydrogen with flammability ratio 180:1<--->34:1 makes for massive quantities of NOx's

Hydrogen works wonders in a fuel cell although the cost is 4 times for Hydrogen vs Hydrocarbons.

Okie
 
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DocLightning
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 9:28 pm

Let's just assume that we figure out how to power planes with H2 or batteries or liquified natural unicorn farts (LCUF, it's all the range) or even fusion reactors.

Why does that suddenly change the calculus around the number of fans you want (they're not "engines" unless they run by the expansion of a working fluid)? Fans are heavy, require fancy materials to handle the mechanical stresses, and require maintenance. Also, machinery with high-speed rotating parts always runs a risk of an uncontained failure. If you double the number of fans, you double the risk of an uncontained failure.

For ships, a single propeller is most efficient, but many passenger ships have 2-4 props because a single propeller would have too much diameter and then make the draught too deep. The same is true with airplane propulsors; each additional one adds additional inefficiencies, both aerodynamic and operational/maintenance.

I don't think that we will ever see a passenger aircraft with only one fan, because then it would need to be 100% failproof and that's an impossible requirement, but there are many reasons to stick with no more than two that have nothing to do with fuel efficiency.
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GalaxyFlyer
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Jan 20, 2021 10:34 pm

Hydrogen fuel to equal kerosene would require massive storage capacity as it is very light while having 3 times the specific energy of kerosene, it’s one-sixth the density by volume. You have to overcome is low volumetric energy density. Cryogenic storage (-253c) adds huge weight and spherical containers, so it won’t be wing tanks.

We’re not flying around in planes that look like they did 60 years ago for no good reason.
 
LH707330
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Thu Jan 21, 2021 3:51 am

DocLightning wrote:
Let's just assume that we figure out how to power planes with H2 or batteries or liquified natural unicorn farts (LCUF, it's all the range) or even fusion reactors.

Why does that suddenly change the calculus around the number of fans you want (they're not "engines" unless they run by the expansion of a working fluid)? Fans are heavy, require fancy materials to handle the mechanical stresses, and require maintenance. Also, machinery with high-speed rotating parts always runs a risk of an uncontained failure. If you double the number of fans, you double the risk of an uncontained failure.

This is why we're unlikely to see hydrogen-powered quads. Here's some fun reading on the topic if you're interested: https://leehamnews.com/tag/hydrogen-aircraft/

Tl;dr: hydrogen might work for an A320 replacement, but the further out your range requirement goes, the more cumbersome it becomes to store the stuff because:

GalaxyFlyer wrote:
Hydrogen fuel to equal kerosene would require massive storage capacity as it is very light while having 3 times the specific energy of kerosene, it’s one-sixth the density by volume. You have to overcome is low volumetric energy density. Cryogenic storage (-253c) adds huge weight and spherical containers, so it won’t be wing tanks.

We’re not flying around in planes that look like they did 60 years ago for no good reason.
 
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Francoflier
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Thu Jan 21, 2021 7:17 am

I don't see hydrogen being used in a jet engine. The poor propulsive efficiency would require carrying too much of it. Its only potential future in aviation would be as a source of fuel for fuel cells to generate electricity for electric turbines where the overall higher efficiency would reduce the required H2 uplift. Although there are still many technological hurdles to overcome before we get there.

Until then, the best bet for a planet-friendly aviation is synthetic jet fuels, which can be mostly carbon neutral depending on the manufacturing process and its source of power, even carbon negative through carbon capture technology. The technology is almost there, the trick is making it cost effective.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
IADFCO
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Fri Jan 22, 2021 5:00 am

All the technical arguments above make perfect sense.

The issue is political, i.e., if someone at some point will decide that conventional aviation fuels pollute too much, and clean fuels must be used, even if everybody agrees that they are not the best economic and probably engineering choice. I don't think that that kind of decision is likely any time soon, but it is not entirely out of the question.

At that point, hydrogen may very well be the next best (and feasible) option, even if all airliners would look like Belugas.
 
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lightsaber
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sat Jan 23, 2021 5:06 pm

DocLightning wrote:
Let's just assume that we figure out how to power planes with H2 or batteries or liquified natural unicorn farts (LCUF, it's all the range) or even fusion reactors.

Why does that suddenly change the calculus around the number of fans you want (they're not "engines" unless they run by the expansion of a working fluid)? Fans are heavy, require fancy materials to handle the mechanical stresses, and require maintenance. Also, machinery with high-speed rotating parts always runs a risk of an uncontained failure. If you double the number of fans, you double the risk of an uncontained failure.

For ships, a single propeller is most efficient, but many passenger ships have 2-4 props because a single propeller would have too much diameter and then make the draught too deep. The same is true with airplane propulsors; each additional one adds additional inefficiencies, both aerodynamic and operational/maintenance.

I don't think that we will ever see a passenger aircraft with only one fan, because then it would need to be 100% failproof and that's an impossible requirement, but there are many reasons to stick with no more than two that have nothing to do with fuel efficiency.

Expanding on this, the propeller on an aircraft should be shrouded to reduce noise. The more propellers, the greater the shroud weight and more shroud drag.

Now BwBs will have three (or 4) as an artifact of no rudder. Twin fans on a BWB must be far enough apart to theoretically survive flying through a flock of geese and that creates issues without a vertical stabilizer.

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Zeke2517
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 5:31 am

I think, to put it simply, even if there is a revolution in efficiency and fuel prices and alternative fuels, etc, running more than two engines is less efficient.

So say, for the sake of argument, that they figure out how to power an intercontinental jet airliner with hydrogen in a reasonable fashion. They aren’t going to say, “Huzzah! Let’s use four engines now because 747s were cool!” No, they are going to use two, because it is more efficient even if they don’t have to pull oil out of the ground. If they didn’t need redundancy they would use one.

The mass and density of hydrogen and the weight of batteries really don’t matter with regard to the OP’s theory.
 
FlyHappy
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 6:56 am

I dismissed OP's train of logic when I first read this.

And now that I've read the input of many others, far smarter than I.... well, I'll toss in my own hypothetical devil's advocate questions regarding > 2 engine/motor proposition.

for the sake of arguments, lets envision electric motors pushing air, the source of current isn't important (battery/fuel cel/liquified unicorn farts). Lets further stipulate a modest size of payload capacity and range; we are talking RJ sized airliners at most - not hauling cargo, not flying long range. Something designed to move 30 to 80 people and their bags a modest distance, particularly where there are challenges now (terrain, water, etc), and maybe where the existing cost is high, for whatever reason.


motor/fan failure: having 3, 4 or even 5 motors and fans could help in physical layout to mitigate engine out/bird strike yaw/vstab issues, no? how about wing tip and hstab mounted props? max distance to fuselage (wingtip) and no fuse exposure for the hstab mounted props. Even with a BWB config, might two wing tip + two tight central/overbody fans mitigate yaw issues? I get that gear length and rotation are compromised.


prop shrouds: are they absolutely necessary? I realize the Open Rotor project stalled in great part due to noise - but the last t-prop I was up close to was a SAAB 340, and man.... it was LOUD. is it not possible for 4 unshrouded electric fans to be equal or quieter?

systems redundancy: current airliners typically have 3 independent systems for control surfaces (my best understanding). In theory, couldn't a 3/4/5 electric motor driven airliner have independent wiring and possibly power source for similar redundancies? Wouldn't that be advantageous from a safety perspective?

dumb question: current props are all made of metal alloys, yes? given that safety considerations revolve around the kinetic energy of failed rotating parts, are there new materials on the horizon that are prop-suitable and meaningfully reduce weight so that the weight of protective materials (Kevlar?) can be reduced?
 
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Starlionblue
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 7:11 am

With every additional motor/fan, you're adding complexity and losing efficiency. With current jet engine reliability, a pilot is unlikely to see an engine failure in his entire career. So the best combo currently is two engines. Systems aren't really impacted. You can manage sufficient redundancy with two engines, APU and RAT. Additional engines won't improve fault tolerance.

Fan noise is fan noise. It won't be quieter because it is driven by an electric motor. Shrouds also permit higher speeds than normal props.

Current props are not all made of metal. There are plenty of composites around. Large turbofan blades are all composite, I think.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
FlyHappy
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 7:49 am

Starlionblue wrote:
With every additional motor/fan, you're adding complexity and losing efficiency. With current jet engine reliability, a pilot is unlikely to see an engine failure in his entire career.


agreed and understood - but at least my speculations are specifically not about current jet/turbine engines.

Starlionblue wrote:
So the best combo currently is two engines. Systems aren't really impacted. You can manage sufficient redundancy with two engines, APU and RAT. Additional engines won't improve fault tolerance.


again - I get that, but I'm asking to envision the possibility that ecological/political/regulatory forces might bend the curve away from tube/2 wing undermounted engine design for short haul/smaller aircraft? For example, undermount is preferred now due to turbine engine maintenance requirements (which are high) - even despite the compromise of growing fan size/ground clearance, etc. An electric motor presumably requires far less maintenance and so ease of access is less of a consideration/cost.
Isn't it true that many of the current aircraft fulfilling the short haul/small capacity role have no RAT and some have no APU?

Starlionblue wrote:
Fan noise is fan noise. It won't be quieter because it is driven by an electric motor. Shrouds also permit higher speeds than normal props.


Right - but speed for short haul not a big consideration. and.. in the case of my SAAB 340 comparison - is the prop speed not optimized? or does it have a gearbox?

Starlionblue wrote:
Current props are not all made of metal. There are plenty of composites around. Large turbofan blades are all composite, I think.


I see. Did not know.
 
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Starlionblue
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 9:26 am

FlyHappy wrote:
Starlionblue wrote:
With every additional motor/fan, you're adding complexity and losing efficiency. With current jet engine reliability, a pilot is unlikely to see an engine failure in his entire career.


agreed and understood - but at least my speculations are specifically not about current jet/turbine engines.

Starlionblue wrote:
So the best combo currently is two engines. Systems aren't really impacted. You can manage sufficient redundancy with two engines, APU and RAT. Additional engines won't improve fault tolerance.


again - I get that, but I'm asking to envision the possibility that ecological/political/regulatory forces might bend the curve away from tube/2 wing undermounted engine design for short haul/smaller aircraft? For example, undermount is preferred now due to turbine engine maintenance requirements (which are high) - even despite the compromise of growing fan size/ground clearance, etc. An electric motor presumably requires far less maintenance and so ease of access is less of a consideration/cost.
Isn't it true that many of the current aircraft fulfilling the short haul/small capacity role have no RAT and some have no APU?

Starlionblue wrote:
Fan noise is fan noise. It won't be quieter because it is driven by an electric motor. Shrouds also permit higher speeds than normal props.


Right - but speed for short haul not a big consideration. and.. in the case of my SAAB 340 comparison - is the prop speed not optimized? or does it have a gearbox?

Starlionblue wrote:
Current props are not all made of metal. There are plenty of composites around. Large turbofan blades are all composite, I think.


I see. Did not know.


Undermount is only partly driven my maintenance. Maintenance is far from the main major consideration. Mounting the engine below and in front of the wing keeps it in clean airflow, counteracts wing twisting moment and counteracts wing bending moment. This translates to massive weight reduction compared to mounting it somewhere else. It is an ideal engine location for subsonic and transonic aircraft in most respects, except for ground clearance.

A fan is a fan regardless of what is driving it. Driving it with an electric motor or whatever doesn't change the aerodynamics. Large electric motors easily have enough torque to drive a big fan, so there's no reason to increase the number of fans if you implement electric propulsion.

The Saab 340 uses the GE700 turboprop, which does indeed have a propeller gearbox. However, again, a fan or prop is the same noise-wise whatever drives it. You could drive the A340 prop with an electric motor and it would make only barely less noise.

Some small turboprops indeed have no APU and no RAT. They're small enough that the flight controls don't need augmentation.

There are advantages to mounting the fans somewhere else than underwing. Airbus and Boeing concepts in the past decade have certainly shown a fair share of tail-mounted engines. What they haven't shown is a significantly larger number of fans than two.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
FlyHappy
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 10:02 am

Starlionblue wrote:
Undermount is only partly driven my maintenance. Maintenance is far from the main major consideration. Mounting the engine below and in front of the wing keeps it in clean airflow, counteracts wing twisting moment and counteracts wing bending moment. This translates to massive weight reduction compared to mounting it somewhere else. It is an ideal engine location for subsonic and transonic aircraft in most respects, except for ground clearance.


clean airflow - electric motors far smaller and lighter than turbines, and if wing not used for fuel/structure for heavy engines, then "clean air" can perhaps be reasonably achieved with thinner wings, creative mountings - overwing/wingtips, some of these can benefit moment issues.... what about older "pusher" configurations - those were done for some reason?

Starlionblue wrote:
The Saab 340 uses the GE700 turboprop, which does indeed have a propeller gearbox. However, again, a fan or prop is the same noise-wise whatever drives it. You could drive the A340 prop with an electric motor and it would make only barely less noise.


okay - here's a crazy thought; with larger number of smaller motors and fans, it would allow an aircraft to taxi with some fans idle, minimizing noise? Even other phases of flight beyond most demanding (take off/initial climb), some fans could idle or feather... unlike ICE, electric motors instantly produce max torque and there's little fear of not "starting".

Starlionblue wrote:
There are advantages to mounting the fans somewhere else than underwing. Airbus and Boeing concepts in the past decade have certainly shown a fair share of tail-mounted engines. What they haven't shown is a significantly larger number of fans than two.


always appreciate your input, S'blue. Still trying to figure out if your Avatar is holding a silenced pistol.
 
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Starlionblue
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 10:53 am

FlyHappy wrote:
Starlionblue wrote:
Undermount is only partly driven my maintenance. Maintenance is far from the main major consideration. Mounting the engine below and in front of the wing keeps it in clean airflow, counteracts wing twisting moment and counteracts wing bending moment. This translates to massive weight reduction compared to mounting it somewhere else. It is an ideal engine location for subsonic and transonic aircraft in most respects, except for ground clearance.


clean airflow - electric motors far smaller and lighter than turbines, and if wing not used for fuel/structure for heavy engines, then "clean air" can perhaps be reasonably achieved with thinner wings, creative mountings - overwing/wingtips, some of these can benefit moment issues.... what about older "pusher" configurations - those were done for some reason?

Starlionblue wrote:
The Saab 340 uses the GE700 turboprop, which does indeed have a propeller gearbox. However, again, a fan or prop is the same noise-wise whatever drives it. You could drive the A340 prop with an electric motor and it would make only barely less noise.


okay - here's a crazy thought; with larger number of smaller motors and fans, it would allow an aircraft to taxi with some fans idle, minimizing noise? Even other phases of flight beyond most demanding (take off/initial climb), some fans could idle or feather... unlike ICE, electric motors instantly produce max torque and there's little fear of not "starting".

Starlionblue wrote:
There are advantages to mounting the fans somewhere else than underwing. Airbus and Boeing concepts in the past decade have certainly shown a fair share of tail-mounted engines. What they haven't shown is a significantly larger number of fans than two.


always appreciate your input, S'blue. Still trying to figure out if your Avatar is holding a silenced pistol.



It is very much misunderstood how forces act on the wings. Hanging heavy engines on them and filling them with fuel counteracts the much greater lift forces acting on them, which allows a lighter structure.

The engines mounted under the wing don't have a big effect on the structural weight. The fuselage being held up by the wings is the main driver of wing structure. That won't change if you change the engines. Fuel in the wings allows for a lighter structure as it counteracts wing bending moment. If you made a large electric aircraft, you'd want the batteries in the wings.

We already taxi at idle most of the time. Taxi noise is not a big deal compared to take-off and approach noise. And having fans at idle in the cruise is inefficient. Better to have them working at 75-85% of max aerodynamically. This does not change if you're driving them electrically.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
GalaxyFlyer
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 2:54 pm

Approach noise is no longer primarily driven by engines, but aerodynamics, too.
 
CaptainHaresh
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 24, 2021 5:10 pm

mxaxai wrote:
GalaxyFlyer wrote:
https://energypost.eu/hydrogen-fuel-cell-cars-competitive-hydrogen-fuel-cell-expert/


You cannot fill up like you do with gasoline or diesel. It is actually pretty ridiculous how hard it is to fill up a HFC powered car
You won’t even go 100 miles on current tech hydrogen tanks that are still safe to carry around in a car
Fuel cells wear out crazy fast and are hard to regenerate
Hydrogen as a fuel is incredibly hard to make and distribute with acceptably low losses

That's just factually wrong, though losses are indeed higher than for battery powered vehicles. Compare for example https://pubs.rsc.org/en/content/article ... ivAbstract
The Toyota Mirai has a range >300 miles, with >500 miles planned on the next version.
Hydrogen stations exist and are about as easy to operate as regular gas stations or current electrical systems.
Current automobile fuel cells have a projected lifespan of approx. 6,000h, similar to ICE or batteries.


Now, I fundamentally agree that batteries are a better form of renewable energy storage for cars.

But there are some applications where hydrogen makes sense. The largest problem is that it requires completely new infrastructure for the expected volumes. For large & long-range applications, for example trains, trucks, ships and stationary industrial systems, hydrogen starts to become advantageus compared to batteries (and gasoline). This is partially because hydrogen benefits from upscaling more than batteries, and partially because those applications can avoid the logistical issues that come with hydrogen distribution.

Many companies that traditionally relied on ICE are investing heavily into industrial hydrogen systems, for example Shell, Volvo, Daimler & Iveco: https://www.shell.com/energy-and-innova ... scale.html

On aircraft, neither hydrogen nor batteries can be a 1-for-1 replacement for the current propulsion systems. Yet, unless batteries make huge leaps in the next 10-20 years, future aircraft with a meaningful range and payload will have to be powered by either hydrogen or kerosene.



Hydrogen is an indirect greenhouse gas.
Losses during production, transport and use can easily cancel any environmental advantage while increasing the safety risk.
Hydrogen is flammable at a mixture of only 4% in air volume which is close to nothing.
Numerous accidents happen with lead-acid batteries because they generate hydrogen when they are close to fully charged.
The smallest spark can cause the hydrogen to ignite and the battery to explode.
 
Brystar45
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Fri Jan 29, 2021 3:56 am

https://airwaysmag.com/industry/innovat ... aerospace/

Credits to Airways Magazine for the article. This is interesting a Plane that is a Hybrid I can definitely see this as a future along with Water Powered aircrafts too!

Carbon Neutral will be more and more common in the future it seems and synthetic fuels too, plus it would be great to see different design aircrafts I want to see more unique designs be in Passenger use as well.
Going for my goals of being in the Aerospace Industry, Traveling the world and more!
 
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LukaJ
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sat Jan 30, 2021 1:29 am

While the science for this is debatable, aeronautical creativity is still always interesting to me.
I am also in Embry-Riddle. Good luck to you getting your Master's!
When you mentioned Tri-Jets, I just visualized a new tri-jet aircraft with the engines from the Max/NEO. Lol, what that would look like!
 
744SPX
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 31, 2021 1:32 am

Actually when you start talking about electric and distributed propulsion and particularly actively assisted laminar flow/lift enhancement over wings then 4 (or more) "engines" (propulsors) are indeed significantly more efficient than 2. Some proposals show at least 12.

I'm guessing this is what the OP was getting at...
 
744SPX
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Sun Jan 31, 2021 1:41 am

Even if you are just talking conventional gas turbines, there are situations where 4 engines is more efficient than 2. With VLA aircraft there is a limit based on ground clearance and drag issues from the fan cowling. (unless you want to go open rotor, but even then, you are going to have even greater ground clearance issues if its just one engine per wing.

Unless people are willing to move to open rotor, ever higher BPR's are going to hit a limit on large engines where cowling drag will result in greater efficiency losses than using more engines will.

With open rotor efficiency being solid double digits higher than equal tech cowled turbofans, it would also be more efficient to use 4 open rotor engines than two cowled turbofans on a given aircraft. That is regardless of speed, as NASA proved with its ATP project that open rotor maintains the double digit efficiency advantage at even .9 mach.
 
Brystar45
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Feb 03, 2021 1:02 am

Credits to Aviation International News for this article This is amazing Hydrogen Propulsion Aircraft plan for sub regional! Thats a great way to start, to start small and gradually build from there.

https://www.ainonline.com/aviation-news ... l-aircraft
Going for my goals of being in the Aerospace Industry, Traveling the world and more!
 
GalaxyFlyer
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Feb 03, 2021 1:38 am

Magically, LH2 just enters the propulsion system. How?
 
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Starlionblue
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Re: Quad and Tri Jets will come back in the skies "What is old is new again" Alternative fuels and good news!

Wed Feb 03, 2021 2:02 am

GalaxyFlyer wrote:
Magically, LH2 just enters the propulsion system. How?


With a yellow arrow, that's how!

8-)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

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