Why electric planes are inevitable

Dan Thomas said:
The battery energy lost to heat needs to be addressed and accounted for, as does the motor's heat. Battery-electric drive is not 100% efficient either, but it's a lot better than ICE.
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Actually discharging a battery causes it to heat up. Same for charging. So most of the time, cooling is the primary concern. The flight school in Norway (I think), actually warms the battery/cabin under charge so everything starts nice and toasty. After that, the actual flying discharges enough power that they actually cool the battery back. The flight school said they have not seen any material change in battery life if the plane and battery are preheated while connected to the charger. The prop power consumption is significantly more dominant than maintaining cabin/battery temps.

Tim
 
Dan Thomas said:
The recharge times and type of operation is the drawback. Weather also figures into it. A 30-minute range to a 20-minute destination doesn't work if there's no charging facility, or if rapid turnaround to get back for another flight is on the schedule. Harbour Air flies floatplanes, and not many of their destinations will have those charging stations. I've been along that coast and while the islands are mostly populated to some degree, much of it is as remote and rugged and rough as it was a thousand years ago. Its weather can change in just a few minutes, flights sometimes have to divert or turn around, and if you're past the halfway point of that battery, you're up the creek. Landing out in the Strait, with its winds and strong currents, with no power, is a risky deal almost anytime.
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HarborAir and CapeAir, and related keep most aircraft in hubs with quick turns at remote locations with a few spare aircraft pre-positioned at the remote site. So for electric aircraft, they would either need to have capacity to round trip effectively on a single charge or plan on switching aircraft for each flight. When you watch the video, you see that CapeAir have six flights to a single location during peak season, as a result most of the planes only fly a few times a day. So there is a lot less turn time and demand than people expect thinking of traditional airlines.

Reminder, they fly very old planes, that have low CapEx and high OpEx since demand is for only a few flights a day from many locations generally all around the same time.

Tim
 
"Planes don't make money sitting on the ground" - Herb Kelleher
 
tspear said:
HarborAir and CapeAir, and related keep most aircraft in hubs with quick turns at remote locations with a few spare aircraft pre-positioned at the remote site. So for electric aircraft, they would either need to have capacity to round trip effectively on a single charge or plan on switching aircraft for each flight. When you watch the video, you see that CapeAir have six flights to a single location during peak season, as a result most of the planes only fly a few times a day. So there is a lot less turn time and demand than people expect thinking of traditional airlines.

Reminder, they fly very old planes, that have low CapEx and high OpEx since demand is for only a few flights a day from many locations generally all around the same time.

Tim
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Yes, that's why I suggested battery tech would have to improve. If they could get 2+ hour endurance including reserve, that would be enough in many cases for an airplane to fly its whole route and back to base with VFR reserve before needing to recharge. We're not there now, but it's not beyond possibility, unlike some of the predictions we see about electric airplanes.
 
bflynn said:
"Planes don't make money sitting on the ground" - Herb Kelleher
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True whether recharging a battery or sitting in the hangar for maintenance on a fussy reciprocating engine with its accessories and fuel system. Time will tell, now that we actually have certified electric planes in flying school fleets.
 
David Megginson said:
My understanding (not a chemist or engineer) is that degradation in li-ion battery capacity is primarily linked to charge cycles, not calendar time. So if you're using your EV to commute 150 km round trip to work every day and then plugging it in every night, the capacity will fall sooner than if you're charging it 1x/week and then using it for occasional short shopping trips (etc) around your area — and, of course, there would be a whole spectrum in-between. It wouldn't be surprising if both you and @Jeff767 are seeing different results due to different usage patterns.
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Another item I've read about it is the high powered chargers do more "damage"/wear-and-tear on the batteries than lower powered charging at home.

David Megginson said:
And back to aviation, I noticed that the Pipistrel Velis Electro is initially certified for only 500 hours flight time between battery "overhaul" (not sure what they mean by that — replacement?), but they intend to extend it to longer. They probably need to collect field data to prove to EASA that the battery capacity is still sufficient after 500 hours' use, then will gradually get it pushed back.
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That would make them rather pricey if it's stuck at 500 hrs.
 
David Megginson said:
True whether recharging a battery or sitting in the hangar for maintenance on a fussy reciprocating engine with its accessories and fuel system. Time will tell, now that we actually have certified electric planes in flying school fleets.
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Except that the electric planes would have to sit there after EVERY flight, or maybe two short training flights. An ICE plane would be in for repairs occasionally.

I think it would be very valuable for flight schools if the batteries could be quickly removed/replaced to charge them while the next flight is in the air. Probably way too much trouble between the FAA and the weight of the batteries.
 
David Megginson said:
You make some great points about EVs and battery tech in the rest of the post, but "tremendous amount of power" sounds like a red herring. Pipestral's fast charger draws a maximum of 20 kW for each plane while actually charging; a high-end clothes dryer or convection oven draws 5 kW. So a flight school's power usage charging a few planes at the same time would be comparable to that of a public laundromat or large restaurant kitchen during a rush.
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They also show 40kW on the charger and 400V.

They are claiming 15-20 min recharge time, which is not too bad. Then one hour of flight time plus reserve. Looking at my logbook, that might be doable. Most of my flights were longer than that, but that included taxi time. I have several that were around 1.5 hours long, plus cross country flights up to 3 hours. Nothing that couldn't be worked around, but the one hour limit would impact "cross country" time options.

A plane with more range would need more batteries, and therefore more charging time, more power or both. A traveling plane (Bo/Mooney/Cirrus/etc) would need a lot more battery power.
 
David Megginson said:
You make some great points about EVs and battery tech in the rest of the post, but "tremendous amount of power" sounds like a red herring. Pipestral's fast charger draws a maximum of 20 kW for each plane while actually charging; a high-end clothes dryer or convection oven draws 5 kW. So a flight school's power usage charging a few planes at the same time would be comparable to that of a public laundromat or large restaurant kitchen during a rush.
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The Pipestral has a vastly smaller battery capacity than a successful version will have. I am also having a hard time with their numbers. A Tesla fast charger is rated at up to 250 KW’s. Most are 150 and take 45 minutes to an hour to actually charge a 80kw battery pack from 5 to 100%. They are much faster from 20 to 80% with about 20 minutes being average. My Tesla home charger is on a 60 AMP circuit. Nothing else in the house is over 30. The home charger needs all night even with 60 Amps to go from 5% to 100%. It’s far less power than the fast chargers mentioned above.
 
bflynn said:
You know, I've had an EV (Leaf) for three years and I haven't seen anything this extreme

My range is down from 164 to 162, 1.2% in three years. Maybe that will accelerate as it gets older, but I'm not seeing anything that would qualify as "significant range degradation". If I do, I hope there will be a relatively inexpensive replacement option that uses a better battery technology.

For now, my "mileage" is steady at 4.3 miles/kw, but that does drop to 4.0 in the winter, which is only a 6.98% drop.

I don't pay attention to charge times since the car is just sitting out in the garage while I'm eating dinner, so I can't comment on that. I don't see a loss from my car sitting at the airport. I've left it for 3 weeks once for a business trip that got extended and the battery charge showed exactly what it was when I left.

BTW, if you're only flying once every 6 weeks, get out and fly more. You've got an electric plane, it costs pennies to operate.
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Some manufacturers choose to restrict the capacity of the battery pack to less than its actual capacity. As the battery degrades over time they release that extra capacity to maintain the published capacity. Tesla does not do this as they want to publish the highest possible range in EPA tests.
 
wayne said:
A traveling plane (Bo/Mooney/Cirrus/etc) would need a lot more battery power.
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I really don't think that will happen. The weight equation just doesn't work out for aviation, even assuming the lightest possible composite airframe and a 4x improvement in battery tech.

I think we'll see electric airplanes that have decent endurance, decent speed, or decent range, but not decent endurance, decent speed, and decent range. We're still on initial upslope of the Gartner hype cycle, where zealots are dreaming of all aircraft becoming electric; when that doesn't happen, we'll drop into Gartner's trough of disillusionment, where the skeptics' voices are loudest (but equally wrong), and eventually, we'll settle in the middle, using electric planes where they make sense, and not trying to use them where they don't. It's a sadly-predictable pattern for all new tech.

1280px-Gartner_Hype_Cycle.svg.png
 
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David Megginson said:
I really don't think that will happen.
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I don’t know about never, but it will take some significant improvements in battery tech; not 4x, but more than 10x. You’re absolutely right, currently it’s not possible. The batteries would simply weigh too much.
 
For local flights in a private electic plane, drip charging would be fine: go up for a flight, land, then plug in to a regular electric outlet to recharge overnight, just like people do with their electric cars. It's high-use rental planes or long, multi-stop cross country flights that will be the challenge. And batteries do need to get up to 1,500 or 2,000 hours TBR if there's going to be a real cost advantage to electric, even for the applications where it will work well.
 
bflynn said:
"Planes don't make money sitting on the ground" - Herb Kelleher
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Look at the plane selections of CapeAir, AirHarbor... There are a half dozen of these companies that I have read about. All of them run old planes, which are fairly cheap to acquire and expensive to run.
Yet these companies stay in business, and the companies which try and solve the same flights with expensive new turbine powered equipment go out of business.

Why? Because this niche is limited seats, limited flights per day to multiple locations, all occurring around the same time. Also due to the remote nature of the secondary airports, you either need to pay a lot for mechanics to be onsite and available, or you preposition extra gear there waiting in case of mechanical failure. I have seen this happen with CapeAir; pilot is pre-flighting the plane, finds an issue, and takes the next plane in line. Think about the case study in the video which started the thread. That is an average of six flights at half capacity, so roughly 30 people a day. That demand is just too low for have large CapEx sitting around.

Tim
 
Tantalum said:
Yep, that's why I drip chargers work the best for optimal battery health
The leap needed is truly massive
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Depends on the battery chemistry and the battery management system. For example, on the Nissan Leaf, A level 1 charge or a Level 3 are both bad for battery. A level 2 charge is the optimal charger for the battery.
We would need a lot more information to make a determination, and I would guess that Pipistrel and anyone else who builds an electric airplane would have the guts to give the proper information to owners.

Tim
 
David Megginson said:
For local flights in a private electic plane, drip charging would be fine: go up for a flight, land, then plug in to a regular electric outlet to recharge overnight, just like people do with their electric cars. It's high-use rental planes or long, multi-stop cross country flights that will be the challenge. And batteries do need to get up to 1,500 or 2,000 hours TBR if there's going to be a real cost advantage to electric, even for the applications where it will work well.
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A regular outlet charges a typical electric car at a rate if 2 to 3 miles per hour. Plug it in overnight and you will get about 30 miles additional range in the morning. A typical level 2 charger will fully charge a 80KW battery overnight but requires a minimum 30 amp 240 bolt dedicated circuit. Tesla home charges can take up to 80 AMP inputs. Most houses are on a 200 Amp circuit.
 
tspear said:
Look at the plane selections of CapeAir, AirHarbor... There are a half dozen of these companies that I have read about. All of them run old planes, which are fairly cheap to acquire and expensive to run.
Yet these companies stay in business, and the companies which try and solve the same flights with expensive new turbine powered equipment go out of business.

Why? Because this niche is limited seats, limited flights per day to multiple locations, all occurring around the same time. Also due to the remote nature of the secondary airports, you either need to pay a lot for mechanics to be onsite and available, or you preposition extra gear there waiting in case of mechanical failure. I have seen this happen with CapeAir; pilot is pre-flighting the plane, finds an issue, and takes the next plane in line. Think about the case study in the video which started the thread. That is an average of six flights at half capacity, so roughly 30 people a day. That demand is just too low for have large CapEx sitting around.

Tim
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Cape Air averages 3.7 hours per day on their 402 fleet including aircraft in for maintenance. Considering their average flight is under 40 minutes that’s a lot of flights per year. They are retiring the 402’s and replacing them with Tecams.
 
Jeff767 said:
A regular outlet charges a typical electric car at a rate if 2 to 3 miles per hour. Plug it in overnight and you will get about 30 miles additional range in the morning.
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I think 4 miles of EV range per hour of charging on 120v is more typical. We easily go from 0 to max (typically 40 to 50 miles) overnight. Feed 240v into the stock EVSE cable bumps it up to 10 miles per hour, handy for top offs during the day. Of course, as a PHEV we never have range anxiety on trips where we just treat the car as a conventional 42 mpg hybrid.
 
wilkersk said:
https://www.homebuiltairplanes.com/...raft-will-never-have-significant-range.28680/
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Hybrids work well in cars because of stop and go traffic and hills. On a flat highway, a hybrid is a terrible solution. You drain the batteries quick and then you're just paying to haul them around. For the same reason, a hybrid aircraft doesn't work. You've drained the batteries and then some by the time you finish your climb, and for cruise you're just hauling around batteries and an elecric motor. If you're lucky you might get 75% recharge on the way back down.

A hybrid in the sense of a diesel locomotive is a bit better, but that type has the inefficiency issues. A train engine needs to weigh a lot. An airplane doesn't do well heavy.
 
Jeff767 said:
Cape Air averages 3.7 hours per day on their 402 fleet including aircraft in for maintenance. Considering their average flight is under 40 minutes that’s a lot of flights per year. They are retiring the 402’s and replacing them with Tecams.
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Not as high as you think. KBOS and KMVY is a typical flight. Based on flightaware, between twenty and twenty five minutes is the standard flight time from KBOS to KNVY for a 402. flyplan.com gave me 23 minutes for flight time.
CapeAir's website gave me 40 minutes, that means they likely are turning the props for 40 minutes with flight time of of 25 minutes. Since I fly in this area, and over KBOS often enough, five minute taxi and run up at KMVY, and ten at KBOS seems about right.
So your 3.7 is closer to 2.3 hours of flight time.

Tim
 
Salty said:
Hybrids work well in cars because of stop and go traffic and hills. On a flat highway, a hybrid is a terrible solution. You drain the batteries quick and then you're just paying to haul them around.
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I'm not disputing what you're saying about electric airplanes, but as far as cars go, my 2003 Civic Hybrid gets over 50 mpg on a level highway. I wouldn't call that a terrible solution. (It doesn't draw from the batteries at all unless I'm going uphill or accelerating.)
 
Palmpilot said:
I'm not disputing what you're saying about electric airplanes, but as far as cars go, my 2003 Civic Hybrid gets over 50 mpg on a level highway. I wouldn't call that a terrible solution. (It doesn't draw from the batteries at all unless I'm going uphill or accelerating.)
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If it’s not even using the battery then it would be even more efficient without the electric motors and batteries.
 
Salty said:
If it’s not even using the battery then it would be even more efficient without the electric motors and batteries.
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The lack of regenerative braking would hurt efficiency, and the lack of electric motor assistance would degrade acceleration and uphill performance.
 
Salty said:
Hybrids work well in cars because of stop and go traffic and hills. On a flat highway, a hybrid is a terrible solution. You drain the batteries quick and then you're just paying to haul them around. For the same reason, a hybrid aircraft doesn't work. You've drained the batteries and then some by the time you finish your climb, and for cruise you're just hauling around batteries and an elecric motor. If you're lucky you might get 75% recharge on the way back down.

A hybrid in the sense of a diesel locomotive is a bit better, but that type has the inefficiency issues. A train engine needs to weigh a lot. An airplane doesn't do well heavy.
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Hybrids even on highway driving work well. Go back to the original Prius, it used an undersized gas engine, that basically had enough power for optimal cruise at highway speeds on level ground. Going uphill, the car used the battery and the electric assist, going downhill the battery was recharged.
The result, it got much better MPG then comparable vehicles.

Tim
 
I owned a Prius. It was great in the city. Not great on the highway.
 
Salty said:
I owned a Prius. It was great in the city. Not great on the highway.
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My Honda hybrid gets better mileage on the highway than in the city. The Prius was opposite of that when I looked at them. I think it has to do with differences in when they use the gas engine and when they use the electric motor.
 
The current Honda CRV hybrid is rated at 40 city and 35 highway. That’s pretty much the norm for most hybrids.
 
Jeff767 said:
The current Honda CRV hybrid is rated at 40 city and 35 highway. That’s pretty much the norm for most hybrids.
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I’m sure I’ve mentioned this before, but our Honda Clarity PHEV regularly returns around 42 calculated mpg on trips where charging is not practical. This in a car the approximate size of of an Accord.
 
Jeff767 said:
The current Honda CRV hybrid is rated at 40 city and 35 highway. That’s pretty much the norm for most hybrids.
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There doesn't seem to be a Civic hybrid on their Web site anymore, so there isn't a direct comparison, but I see that the Insight hybrid, which is a better comparison to my Civic than the CR-V is, also has better mileage in the city than on the highway. They must have changed their design approach since 2003.

https://www.caranddriver.com/honda/insight
 
Palmpilot said:
My Honda hybrid gets better mileage on the highway than in the city. The Prius was opposite of that when I looked at them. I think it has to do with differences in when they use the gas engine and when they use the electric motor.
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.

I believe it is because the Prius uses the Atkinson cycle engine .... which has excellent economy when running at a constant speed to charge the battery .... but at high speeds on long trips the engine is operating flat out which lowers efficiency.

Having said that , I know someone who rents Prius for long trips because it gets about 51 mpg.
Go figure .

.
 
All,

When it comes MPG and hybrids, it really depends on how the car is designed. The system can be tuned for city or highway driving; rarely will it ever be optimal for both.
Most people know that when you press the accelerator on a car, a gas engine at 25% load will generally be much more efficient than one at 90% design output; and this can be seen by looking at the instant MPG calculation on a lot of modern cars.
So, when you look at small cars, you find many have better city than highway mileage. The reason is simple, the gas engine is so undersized for highway driving, it is running at a rather inefficient speed. The compare this to most midsize and larger cars, the weight of the vehicle generally mandates larger engines for acceleration reasons. With air being a much greater factor in drag than rolling resistance caused by weight, the oversized engine will actually be more efficient on the highway than in the city.

Now, most hybrids are tuned for the city, so the gas engine on the highway is working in a non-optimal speed for the engine, just like those small subcompacts. The result is many hybrids have worse gas mileage on the highway.

Tim
 
Do hybrid cars use full alternative ICE powertrains, or just a fuel-powered generator to top up or supplement the battery?
 
Hybrids do not work well on the highway unless there are hills. There is some advantage with hills if they are large enough as you can reclaim some energy going back down. But on flat land a hybrid only gets better milage than a non hybrid due to being lighter and more aerodynamic, which you could do with non-hybrids if people didn't care that they were ugly and louder inside. That is all. Without the ability to reclaim energy, by climbing and descending, or stopping and starting, a hybrid is a handicap. For aircraft, a hybrid is a handicap. Wish all you want, it doesn't change physics.
 
Salty said:
Hybrids do not work well on the highway unless there are hills. There is some advantage with hills if they are large enough as you can reclaim some energy going back down. But on flat land a hybrid only gets better milage than a non hybrid due to being lighter and more aerodynamic, which you could do with non-hybrids if people didn't care that they were ugly and louder inside. That is all. Without the ability to reclaim energy, by climbing and descending, or stopping and starting, a hybrid is a handicap. For aircraft, a hybrid is a handicap. Wish all you want, it doesn't change physics.
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The body of my Civic Hybrid looks identical to that of the non-hybrid Civics of the same year, and the mileage was considerably better than they were. I don't know how the weights compared.

It gets 51 MPG or better on level highways. (The EPA highway mileage is 51.) I don't know whether hilly roads improve that or not.
 
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