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I'm pretty sure you're the one mixing a few things up. Nowhere did I say anything about climbing to 10,000m.
Eviation Alice (Electric Regional Airliner)
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And remember climb L/D is always significantly worse than cruise L/D.
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Its not. They've said that 10k ft is the initial target. Which is reasonable because climbing to 30k would take more than 340kw, or around 40% of the battery just to get to cruise alt.
I said that, this is without any additional losses, not a value for the real world.
@sienar: according to all information that I ve fund, it has a cruise height an top height of 30000 ft. The high cruise speed of about 400 km/h demands a great height to fly efficient.
@Zoo Tycoon : Usually the cruise L/D factor is not the ideal L/D factor, but when you fly that high with a moderate speed, they might match. The Otto Celara is also inteded to fly with constant angle of attac for the best L/D ratio.
Why would anyone in the world built a triangular pressurized fuselage for 30000 ft/10.000 m for a cruise height of only 10,000 ft ???
If the plane would fly slightly lower at 8000 ft it wouldn’t need a pressurisation at all and could have saved a lot of cost and weight.
This doesn’t make sense at all!
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If you want your precious stored electrons to go as far as possible, forget getting there quick, you fly slowly at constant AOA and best glide. Climbing at high AOA loses 20-30% of your L/D compared to the optimal LD cruise for range.
It doesn’t make any sense because they’re so desperate;- desperate times call for desperate measures…..or in this case claims.
At transit altitudes of 10000 ft they’ll be screwed by the weather (the e-vomit) and it’s about the altitude where you really need oxygen, hence pressurisation.
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Well I guess at 250 mph it would be much more efficient to fly higher than 10,000 ft. There is a curve of best L/D which leads to increasing height with increasing speed. I’m not an aircraft expert, but I’m pretty sure, that it would save electrons to fly slower (as you said) at the same height, or higher with the same speed.
Nevertheless, flying just above the pressurization height makes little sense, I guess they are continuously fixing their targets. Sometimes the results simply don’t fit together until the next version…
I wonder how they achieved a super lightweight structure with a triangular fuselage which can be pressurized for 30,000 (totally unnecessary if you cruise at 10,000 ft…)
Nevertheless, flying just above the pressurization height makes little sense, I guess they are continuously fixing their targets. Sometimes the results simply don’t fit together until the next version…
I wonder how they achieved a super lightweight structure with a triangular fuselage which can be pressurized for 30,000 (totally unnecessary if you cruise at 10,000 ft…)
10000ft is the max height a passenger a/c can fly without providing oxygen to all passengers all the time. Today, that means that you need to have a pressurized cabin to fly higher than 10kft.
Density decreases with altitude.
As drag is a function of air density, drag is reduced as you fly higher.
Usually, for a turbine engine or, worst, an internal combustion engine, power output decreases with the drop in air density. What means that, as you fly higher, your engine outputs less power.
EV aircraft's power isn't related to air density and remains ideally unaffected by altitude. Hence, the net available power of such aircraft... Augments with altitude! The higher (and faster) you fly, the more efficient your engine will be fighting gravity and drag. This is unique.
This is where you want to make some good usage of your battery power and not down low under the pretext that having a pressurized cabin increases weight and climb time will draw all your power...
Guess what, if you can spend the extra structural weight to embark your energy requirements in the form of a pack of heavy batteries, you can certainly afford the extra percentage in weight to get your cabin pressurized. You can also climb at a fast speed since your weight Vs wing surface ratio is certainly higher than usual.
Alice's Eviation got it right on the principle. They just need now to prove it can works.
Density decreases with altitude.
As drag is a function of air density, drag is reduced as you fly higher.
Usually, for a turbine engine or, worst, an internal combustion engine, power output decreases with the drop in air density. What means that, as you fly higher, your engine outputs less power.
EV aircraft's power isn't related to air density and remains ideally unaffected by altitude. Hence, the net available power of such aircraft... Augments with altitude! The higher (and faster) you fly, the more efficient your engine will be fighting gravity and drag. This is unique.
This is where you want to make some good usage of your battery power and not down low under the pretext that having a pressurized cabin increases weight and climb time will draw all your power...
Guess what, if you can spend the extra structural weight to embark your energy requirements in the form of a pack of heavy batteries, you can certainly afford the extra percentage in weight to get your cabin pressurized. You can also climb at a fast speed since your weight Vs wing surface ratio is certainly higher than usual.
Alice's Eviation got it right on the principle. They just need now to prove it can works.
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Ah, not really;- while at cruising altitude, thrust just has to equal drag for a given speed. Most gas turbofans are sized for top of climb and after which the engines are throttle back to a thrust much closer to idle than max power. Hence the fact max thrust or power available is less than at sea level is of no consequence. In fact as fuel is burned and mass is lost, a constant throttle setting will give a slow climb with time, which increases the whole mission efficiency. No such thing e aeroplanes.
One of the drawbacks of using a propellor at altitude is it can’t transmit the power into thrust (tip limiting Mach number), so suffers a gradual loss in thrust as altitude increases. So again having a lot of torque and power available does you no good if the propeller won’t turn it into thrust. As pointed out above climbing upstairs uses a lot of power for very little distance. Another problem not often talked about is that for large currents, electrical insulation rapidly losses it properties with increasing altitude so you need a lot more of it, all getting heavy again.
Cabin pressurisation eat a lot of energy as it requires a constant air throughput to purge out the CO2 (and nasty human smells, bowel out gassing, yuk a problem at even 10kft ). The air drawn in needs to be compressed and additionally heated because it’s typically -40 to - 50C A real pain to use your precious onboard electrons.
One of the drawbacks of using a propellor at altitude is it can’t transmit the power into thrust (tip limiting Mach number), so suffers a gradual loss in thrust as altitude increases. So again having a lot of torque and power available does you no good if the propeller won’t turn it into thrust. As pointed out above climbing upstairs uses a lot of power for very little distance. Another problem not often talked about is that for large currents, electrical insulation rapidly losses it properties with increasing altitude so you need a lot more of it, all getting heavy again.
Cabin pressurisation eat a lot of energy as it requires a constant air throughput to purge out the CO2 (and nasty human smells, bowel out gassing, yuk a problem at even 10kft ). The air drawn in needs to be compressed and additionally heated because it’s typically -40 to - 50C A real pain to use your precious onboard electrons.
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The pressure inside pressurized aircraft cabins is usually at an equivalent height of 8000 ft, so flying at 10,000 ft without pressurization will be at least uncomfortable (Especially if the climp should be done within 5 minutes!). It will be truly useless to fly without pressurisation in a plane which is capable to pressurize up to 30,000 ft.
Combustion engines produce enough heat to drive even a triple and maybe a quadruple charging system which can provide constant power up to very great height. The Grob Strato 2C flew up to 70,000 ft. Its just the cost of the pressurization system which makes it a preferred item for the costy turbine planes, but seldom for the cheaper piston powerd planes.
Pressurisation adds a lot of weigh, cost and complexity which is only justified, when you make full use of its advantages, which means you have to fly really high and not barley above the height which can be dealt without pressurization. Pressurisation also adds a lot of weight which you especially can’t afford on an electric plane where useful load is only a small fraction of the total weight. Using a triangular fuselage with pressurisation will result in strong bending moments in the shell which increases weight and thickness.
Flying at best L/D at 400 km/h is only possible at greater height. If the stall speed is sufficient low for a practical aircraft, the plane would produce to much lift at 250 mph/10,000 ft to fly with the best angle of attack. On the other hand, flying higher means you have to invest a lot of energy in climbing which is only justified if you fly long distances or if you regain the energy by gliding down in a flat angle (which is not practical in most cases).
Alice didn’t get it right; their approach doesn’t make sense at all. The other explanation would be, they changed their approach from a high-flying plane to a low flying one without pressurisation. This would be a very logic explanation, since it is a common phenomenon that things must be simplified to make them work, even if it deteriorates the targets. Maybe they are just hoping for better batteries to fulfill the targets without pressurisation.
Combustion engines produce enough heat to drive even a triple and maybe a quadruple charging system which can provide constant power up to very great height. The Grob Strato 2C flew up to 70,000 ft. Its just the cost of the pressurization system which makes it a preferred item for the costy turbine planes, but seldom for the cheaper piston powerd planes.
Pressurisation adds a lot of weigh, cost and complexity which is only justified, when you make full use of its advantages, which means you have to fly really high and not barley above the height which can be dealt without pressurization. Pressurisation also adds a lot of weight which you especially can’t afford on an electric plane where useful load is only a small fraction of the total weight. Using a triangular fuselage with pressurisation will result in strong bending moments in the shell which increases weight and thickness.
Flying at best L/D at 400 km/h is only possible at greater height. If the stall speed is sufficient low for a practical aircraft, the plane would produce to much lift at 250 mph/10,000 ft to fly with the best angle of attack. On the other hand, flying higher means you have to invest a lot of energy in climbing which is only justified if you fly long distances or if you regain the energy by gliding down in a flat angle (which is not practical in most cases).
Alice didn’t get it right; their approach doesn’t make sense at all. The other explanation would be, they changed their approach from a high-flying plane to a low flying one without pressurisation. This would be a very logic explanation, since it is a common phenomenon that things must be simplified to make them work, even if it deteriorates the targets. Maybe they are just hoping for better batteries to fulfill the targets without pressurisation.
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martinbayer
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With unruly passengers more or less regularly misbehaving in every sort of ways these days and all that, I have that uncomfortable notion that airlines might at some point start considering having unconscious travelers on board for most of the flight as a feature rather than a bug...
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and of course turbine engines have a ready supply of compressed air available . . .
cheers,
Robin.
You thinking the wrong way, when you are carrying tons of batteries and the useful load is already down to a very small fraction of the total weight, every additional weight matters extremely. With less than 15 % payload, you can’t afford 5 % more empty weight because even this small extra weight would reduce the payload by one third!
You will know, that pressurized airplanes usually have a limitation for the number of flights because of the stresses involved by pressurisation. In case of a triangular fuselage, this will become much more severe.
You will know, that pressurized airplanes usually have a limitation for the number of flights because of the stresses involved by pressurisation. In case of a triangular fuselage, this will become much more severe.
You have to see it as a system. Electric aircraft are not there to compete in term of performances with more classical setups. Their main advantage remains around their lower operating costs. And then, If you can fly faster from Point A to B, you can make more rotations per day than a similar design. That's where flying higher (and then faster and in more comfortable conditions for your passengers) is paying. Not as a comparison with a turbine aircraft. That's why the inclusion of a pressurized cabin si not to be compared with that of another kind of aircraft but with other electric ones.
Above, the basis of the comparison was with the Tecnam's P-Volt that will fly unpressurized, lower and slower with probably less range. It is possible to argue that the cost of ownership will be comparable. However Eviation design will provide more flight per day with an increased comfort level. Both points will attract more customer, lowering the threshold for their turnover.
Above, the basis of the comparison was with the Tecnam's P-Volt that will fly unpressurized, lower and slower with probably less range. It is possible to argue that the cost of ownership will be comparable. However Eviation design will provide more flight per day with an increased comfort level. Both points will attract more customer, lowering the threshold for their turnover.
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alberchico
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You have to see it as a system. Electric aircraft are not there to compete in term of performances with more classical setups. Their main advantage remains around their lower operating costs. And then, If you can fly faster from Point A to B, you can make more rotations per day than a similar design. That's where flying higher (and then faster and in more comfortable conditions for your passengers) is paying. Not as a comparison with a turbine aircraft. That's why the inclusion of a pressurized cabin si not to be compared with that of another kind of aircraft but with other electric ones.
Above the basis of the comparison was with the Tecnam's P-Volt that will fly unpressurized, lower and slower with probably less range. It is possible to argue that the cost of ownership will be comparable. However Eviation design will provide more flight per day with an increased comfort level. Both points will attract more customer, lowering the threshold for their turnover.
The only potential issue is that the long charging times might limit how many flights can be completed in a day. As of now I believe they are claiming a 1 hour charging time, but that can change if the aircraft undergoes further modifications.
Why should the inclusion of a pressurized cabin not be included when comparing different airplanes? Does a pressurisation really make sense if use it only to increase your cruise height from 8000 to 1000 ft? How much range will you get by flying just 2000 ft higher? Why is there such a high difference between max. ceiling and cruise height?
The lower operating cost have to be confirmed, exchanging the highly specialized batteries every year will cost a fortune. The price for electricity can very a lot depending in which country you are and at what time you charge, it want always be cheaper than Jet-A. Right now, despite the high tax, driving a Diesel car cost less per 100 km than driving an electric car which is recharged at public chargers.
The lower operating cost have to be confirmed, exchanging the highly specialized batteries every year will cost a fortune. The price for electricity can very a lot depending in which country you are and at what time you charge, it want always be cheaper than Jet-A. Right now, despite the high tax, driving a Diesel car cost less per 100 km than driving an electric car which is recharged at public chargers.
Really this is a vanity project, it would make more sense to put this money into 1000 EV taxi's, for a few cities, than waste it on this. There are millions of cars, especially older cars, that need to be replaced, and would make a much quicker improvement in air qual and delepding on where the power comes from, CO2.
I beg to differ. If we are going to move forward at some point air travel also has to be addressed and people have to start somewhere. If this succeeds and Alice's start operating it will be a great first step.
I think even for the US this will work. One has to break the thinking and not compare this to conventional aircraft in terms of range but rather focus upon these operating in shorter hops, often out of small regional airstrips which are often overlooked by mainline carriers. The noise consideration helps greatly here too. I will try to dig up some presentations that better explains what I am trying to say.
AS for the investor aspect, I think it will still be a wise move albeit one that is a more longer term/strategic investment.
AS for the investor aspect, I think it will still be a wise move albeit one that is a more longer term/strategic investment.
alberchico
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Great video that offers an up close look at the prototype. First flight is still a few weeks away. A few screenshots posted below for anyone who can't access the video. The cockpit design is quite impressive.
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alberchico
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View: https://mobile.twitter.com/EviationAero/status/1500986404461068290
Man this aircraft is sure taking it's time to take to the air. They've been saying "first flight in a few weeks" since the initial taxi trials in early December. I wonder if there's some unforeseen technical issue they are grappling with. There's no way they are going to get this complex design certified in only 2 years at this pace. The Tecnam P2012 had its first flight in 2016 and the first revenue flights started in early 2020. And that was a much simpler design.
Man this aircraft is sure taking it's time to take to the air. They've been saying "first flight in a few weeks" since the initial taxi trials in early December. I wonder if there's some unforeseen technical issue they are grappling with. There's no way they are going to get this complex design certified in only 2 years at this pace. The Tecnam P2012 had its first flight in 2016 and the first revenue flights started in early 2020. And that was a much simpler design.
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They are pretty new in this business, to say the least. Better that they take their time than rush it in the air and have an in-flight emergency!
Notice, it's not an over-sized drone piloted from the ground by an up-scaled long haired drone enthusiast unbelievably reaching his twenties. They have real ppl onboard, real money in prototyping and test equipment.
Notice, it's not an over-sized drone piloted from the ground by an up-scaled long haired drone enthusiast unbelievably reaching his twenties. They have real ppl onboard, real money in prototyping and test equipment.
alberchico
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Tuft (aeronautics) - Wikipedia
Looks like they are using a simple but effective method to observe airflow on the wing. This blog has excellent images of the prototype if you look at previous posts.
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martinbayer
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The fact that they misspelled "Charging Port" as "Chargin Port" does not exactly instill confidence.
Great video that offers an up close look at the prototype. First flight is still a few weeks away. A few screenshots posted below for anyone who can't access the video. The cockpit design is quite impressive.
Don't be silly. To me it looks that there has been scuffing etc and that the "G" has simply come off:
Either way, its simply an external marking and I am sure that anyone using it will know what they are doing.
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alberchico
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Still no first flight but this site has some interesting up close images of the prototype. Based on these photos, I assume the avionics compartment is located in the nose. It would be nice if the company uploaded some images of the taxi trials on their twitter page. I understand that these tech startups are secretive, but a few shots of the prototype on the runway isn't exactly giving away proprietary information.
www.alamy.com
Edit: Looks like an update has been posted, the aircraft has apparently resumed high speed taxi trials after a lengthy delay. There must have been some unforeseen technical issue that must have required the aircraft to be taken back to its hangar.
View: https://mobile.twitter.com/photoJDL/status/1507549575518720000
Eviation+aircraft hi-res stock photography and images - Alamy
Find the perfect eviation+aircraft stock photo, image, vector, illustration or 360 image. Available for both RF and RM licensing.
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Edit: Looks like an update has been posted, the aircraft has apparently resumed high speed taxi trials after a lengthy delay. There must have been some unforeseen technical issue that must have required the aircraft to be taken back to its hangar.
View: https://mobile.twitter.com/photoJDL/status/1507549575518720000
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alberchico
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Found a Flickr photo album that has a compilation of all the pictures taken during taxi tests. I particularly like this shot in particular:
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alberchico
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Eviation Signs Deal with Cape Air for 75 All-Electric Alice Commuter Aircraft
/PRNewswire/ -- Eviation Aircraft, a global manufacturer of all-electric commuter aircraft, and Massachusetts-based Cape Air, one of the largest commuter...
www.prnewswire.com
I guess we'll see this plane flying in large numbers in the U.S if all works out.
Eviation was featured on a news show today where it was stated that the first test flights would commence during the summer. That is one heck of a delay considering that taxi trials began in early December. There had to have been some kind of technical issue discovered during taxi trials that needed to be rectified. We finally get to see the massive battery pack in this news clip and it's pretty impressive.
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At least they are the only ones to attempt their first flight with a complete airframe, something that looks like it can be mass-produced rather than being sold in kit without an engine and flight systems...
At this point, we can only speculate about the whereabouts of this delayed first flight but should agree than given the higher level of sophistication of their airframe, nothing should be less surprising given we have here a junior company and a very complex airframe.
At this point, we can only speculate about the whereabouts of this delayed first flight but should agree than given the higher level of sophistication of their airframe, nothing should be less surprising given we have here a junior company and a very complex airframe.
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Joby Aviation did already a lot of flights and proved a range of 150 miles, to me they look like the leader in electric aviation. Elice is still changing the targets (30.000 ft vs. 10.000 ft) and haven’t done a single flight jet. Their claims concerning the range seam to be a bit too optimistic at least…
BTW. Pipistrel is allready selling electric planes.
BTW. Pipistrel is allready selling electric planes.
You are right. Pipistrel is an amazing company with a step ahead of many in that domain. However, their aircraft is built only around a far more modest role than Alice.
Joby Aviation fly what is more an experimental aircraf, not even completed. Their achievements are great but the vaunted commercial applications are a bit far fetched l.
Joby Aviation fly what is more an experimental aircraf, not even completed. Their achievements are great but the vaunted commercial applications are a bit far fetched l.
alberchico
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I've realized I made a mistake regarding the performance figures for this aircraft. I've been saying that it can travel 440nm. Other media outlets have repeated this figure too. I always assumed this was the range with 9 passengers and their bags, but if you look at the company's website, there is a small footnote at the bottom which says " *Target range, zero wind, no payload, IFR reserve". So this is essentially the ferry range. So how far can it travel with a full payload ? There was an aviation blog that speculated that the practical range of the aircraft could be as little as 100nm with stricter EU IFR reserves factored in. It's shocking that the company has not said what the practical range of this aircraft will be. Are they afraid of scaring off potential customers ?
If this aircraft turns out to have really poor range, the complexity of the design ( fly by wire, retractable landing gear, pressurization) means that it will not make any economic sense for any operator to acquire it, it might be better to wait for the Tecnam P-Volt to come to the market.
www.eviation.co
If this aircraft turns out to have really poor range, the complexity of the design ( fly by wire, retractable landing gear, pressurization) means that it will not make any economic sense for any operator to acquire it, it might be better to wait for the Tecnam P-Volt to come to the market.
Aircraft – Eviation
www.eviation.co
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