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Originally Posted by Pilot DAR
(Post 10453271)
Wow, that's a shiny hangar floor!
As a person who flies and certifies aircraft, I would be concerned about a wing or tail low landing causing propeller damage. In any case, I expect that a computer in the plane would have to reduce thrust on a wingtip motor, in the case of a loss of thrust on the other side for any reason. They could be cross shafted like a tilt rotor, but that gets complex and heavy. The V tail would be challenged providing enough yaw control to overcome thrust asymmetry for the wing motors. |
Aeroplanes now! Well I did have one with a supercap that could carry its own weight happily around for nearly 3 minutes.....
The energy density of hydrocarbon fuels is 20-50 times higher than the most advanced Li-ion concept based electrochemical batteries. Wake me up when it's 2-5x higher, and the battery's brisance a fair bit less than good 'ol black-powder. Ye'd do better to use the piddling amount of very expensive renewable energy that we produce to synthesize a better grade of avtur. And if you sit down and think about the chemistry, engineering and economics carefully enough, is the truth of the matter. Mac :ouch: |
Looking at the computer rendering of the Eviation above, the thing that strikes me is that it looks exceptionally lightweight, judging by the doors and stairs, and the landing gear. I know composites can be very strong, this just looks to me like it's pushing the limits.
Of course light weight is an advantage for E-power, but I wonder about compromise with safety in hard landings or actual crashes. Maybe the real thing would be less delicate than the rendering looks at first glance, if it ever makes it into production. |
As said above, it looks like just a dream, without really thinking about it - where does that nosewheel go on retraction; a crosswind will have the props hitting the ground as you kick straight and lower a wing; the tail prop is a worry on rotation for takeoff; asymmetric flight will be a serious problem; and why have 2 sets of airstairs when they could save weight with just one?
There also doesn't look like much room under any floor to place the batteries? They can't be in the tailcone - too far back - and no room in the nose, with the nosewheel strut and wheel, pilot's feet and his big watch. |
Is this a pressurized aircraft, or will it fly in the weather below 10,000 ft.?
Also fast charge rates mean battery life is shortened. |
Originally Posted by Ascend Charlie
(Post 10453471)
As said above, it looks like just a dream, without really thinking about it - where does that nosewheel go on retraction; a crosswind will have the props hitting the ground as you kick straight and lower a wing; the tail prop is a worry on rotation for takeoff; asymmetric flight will be a serious problem; and why have 2 sets of airstairs when they could save weight with just one?
There also doesn't look like much room under any floor to place the batteries? They can't be in the tailcone - too far back - and no room in the nose, with the nosewheel strut and wheel, pilot's feet and his big watch. Could be that the are distributed all over the place, the engine pods look a bit bigger than might be, perhaps some in there as well. As to hitting props on landing you just need to hit the auto-stop button that brings the wing props to a locked horizontal position in about 0.5 seconds. I am almost serious on that one, electric motors can have very high torque for short periods so something like that could be possible. Also means they could go from stop to full power quickly as well. |
In the March 2019 issue of Flying magazine, aerodynamicist Peter Garrison discusses the feasibility of electric airliners. He says he's long been skeptical this would be possible, barring an unexpected revolution in battery technology. However in an even-handed fashion he reviews the challenges and progress to date. He discusses two current electric regional aircraft projects, Eviation and Zunum.
It's a stretch to call Eviation an "airliner", it's about the size/weight of a Pilatus PC12. They will supposedly be displaying a prototype (don't know if it's flyable) in June of this year. Zunum uses ducted fans, but is so far only a paper airplane. The backers of these are not attempting to replace traditional airliners, not even smaller regional jets. They understand battery limitations make that impossible. Rather they are hoping to open a new market for short range low cost air taxi service to smaller airports using 8-10 passenger planes. In essence a similar market and service profile to what VLJs originally planned, notably as promoted by the Eclipse 500. Except the electric planes so far under development will have a range of maybe 600 miles, and Garrison doubts that will be achievable on actual aircraft. |
The other problem not raised here is that the Part 135 requirements of remaining endurance will often exceed the total endurance of the aircraft. Currently proponents of electric aircraft seem to be ignoring standard 14CFR regulations as if they are 'special'. This approach is extended to the safe separation standards between aircraft which will greatly reduce the number of 'Jetsons' that can be airborne in urban areas too.
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First Electric powered and now air powered
New aircraft rises 'like a balloon'By Kenneth Macdonald BBC Scotland special correspondent
Media playback is unsupported on your device Future versions of Phoenix could be fitted with cameras and deployed in surveillance workPhoenix is an unmanned aerial vehicle (UAV) designed to stay in the air indefinitely using a new type of propulsion. Despite being 15m (50ft) long with a mass of 120kg (19 stone) she rises gracefully into the air. She looks a little like an airship, except airships don't have wings. "It's a proper aeroplane," says the UHI's Professor Andrew Rae.As the project's chief engineer, he has overseen the integration of Phoenix's systems. "It flies under its own propulsion although it has no engines," he says. "The central fuselage is filled with helium, which makes it buoyant so it can ascend like a balloon. "And inside that there's another bag with compressors on it that brings air from outside, compresses the air, which makes the aeroplane heavier and then it descends like a glider." Launch satellitesThis ability to "breathe" - to switch quickly between being heavier or lighter than air - doesn't just make the plane go up and down.It is the key to driving it forward. Phoenix is the first large-scale aircraft to be powered by variable-buoyancy propulsion. It moves through the air like a porpoise through water. That means it can travel long distances and stay aloft for long periods. The point? To create a cheaper alternative to launching satellites. https://ichef.bbci.co.uk/news/624/cp...uperblimp3.jpgImage caption Prof Andrew Rae says the Phoenix is a "proper aeroplane" The wings and tail carry solar panels so there is no need to carry fuel aloft. The quasi-airship shape is based on an aerofoil, meaning it also provides lift like its wings do when the plane moves forward. Prof Rae, using two wind tunnels at UHI's Perth College campus, led the design of its aerodynamics. The technique of variable-buoyancy propulsion is already used underwater. The Scottish Association for Marine Science (also part of UHI) has a small fleet of remotely operated vehicles - they call them gliders - that gather data in the North Atlantic. They dive deep to collect data, then rise to the surface to transmit it via satellite. But air is much less dense than water and this has made the principle a trickier proposition for flight. Phoenix is the first aircraft of its size to use it. https://ichef.bbci.co.uk/news/624/cp...uperblimp1.jpgImage caption The central fuselage of the Phoenix is filled with helium It is 15m (49ft) long with a wingspan of almost 11m (36ft) Production versions would need to be scaled up to reach the altitudes of 20km required to fulfil its intended role. An autonomous vehicle which is self-sufficient in energy could stay in the air for days, weeks, even months. The technical term is "ultra-long endurance autonomous aircraft". The team think it could revolutionise the telecommunications industry. 'Almost expendable'The oft-quoted rule of thumb in the space business is that putting a satellite into orbit costs its weight in gold.A Phoenix "pseudosatellite" could do the same job from high in the atmosphere at a fraction of the cost. Prof Rae says some aircraft can already do this but are complex and expensive. Phoenix, by contrast, is so cheap as to be "almost expendable". In addition to UHI, the Phoenix project involves Bristol, Newcastle, Sheffield and Southampton universities. It also involved four commercial companies and three of the UK's Technology Catapults, and has been part funded by the UK government's innovation agency Innovate UK. Winter windsThe prototype Phoenix has been successfully tested inside the Drystack in Portsmouth, a huge indoor area which normally stores pleasure boats.It was used to shelter the aircraft from the winter winds although production versions would operate in all weathers. The project has involved its partners integrating the solar cells, flight control system, micropumps, carbon fibre wings and tail, reversible hydrogen fuel cell and rechargeable battery. The last of these is what enables a solar-powered vehicle to keep working all night. Now that the prototype has flown successfully, the consortium wants to collaborate with major manufacturers to take Phoenix to the next level. |
Originally Posted by Ascend Charlie
(Post 10453471)
As said above, it looks like just a dream, without really thinking about it - where does that nosewheel go on retraction; a crosswind will have the props hitting the ground as you kick straight and lower a wing; the tail prop is a worry on rotation for takeoff; asymmetric flight will be a serious problem; and why have 2 sets of airstairs when they could save weight with just one?
There also doesn't look like much room under any floor to place the batteries? They can't be in the tailcone - too far back - and no room in the nose, with the nosewheel strut and wheel, pilot's feet and his big watch. |
Originally Posted by Ascend Charlie
(Post 10453471)
As said above, it looks like just a dream, without really thinking about it - where does that nosewheel go on retraction; a crosswind will have the props hitting the ground as you kick straight and lower a wing; the tail prop is a worry on rotation for takeoff; asymmetric flight will be a serious problem; and why have 2 sets of airstairs when they could save weight with just one?
There also doesn't look like much room under any floor to place the batteries? They can't be in the tailcone - too far back - and no room in the nose, with the nosewheel strut and wheel, pilot's feet and his big watch. 'Alice' appears to be the same thing - something to bilk money out of gullible investors with no chance of actually working. |
The hype-to-reality ratio in this area is about 50:1 Unless they can prove it flies as advertised then it only proves that anyone can build a website. |
A great deal of the stored energy in an aircraft is getting from ground level to cruise height. But, unlike liquid fuel, once used a battery weight remains. An ‘initial start’ battery pack that would achieve this initial phase then detach and return to base would prevent having to carry the high weight for the endurance of the flight. |
Alice seems to have moved on from being a computer rendered image on a shiny hangar floor to a real prototype st the Paris Airshow. Look here! Presumably arrived by road but apparently due to undergo flight tests this year. |
One big problem with electric aeroplanes is the mains plug... Every time you cross a national boundary you have to change the adapter. Also all those wires get a bit tangled after a while. |
Originally Posted by Andrewgr2
(Post 10499191)
Alice seems to have moved on from being a computer rendered image on a shiny hangar floor to a real prototype st the Paris Airshow.
https://www.airlineratings.com/news/...nterest-paris/ |
Why the conventional landing gear configuration rather than tricycle ? |
Originally Posted by Andrewgr2
(Post 10499191)
Alice seems to have moved on from being a computer rendered image on a shiny hangar floor to a real prototype at the Paris Airshow.
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Originally Posted by Pilot DAR
(Post 10499492)
I opine that there was not enough room to retract the nosewheel.
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They teach them from scratch to fly their electric aircraft in their own school. Said to be one reason to take Cape Air for the first batch of production aircraft.
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