Whatever Happened Too Harbour Air Electric Plane

Cap'n Jack said:
FWIW, you didn't come across as laughing to me, either.
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I don't think there's anything to be gained in diving deeper, unfortunately. I try hard to be sensitive about people's feelings in a lot of areas — gender, race, military service, sexual orientation, religious faith, gender identity, disability, socio-economic status, etc — but if people are going to get upset and defensive even when we discuss electric propulsion (or, in other forums, equally-innocuous topics like universal healthcare, firearms registration, etc.), I'm afraid they'll just have to deal with it. We can't walk around on tip-toes over everything.
 
Salty said:
Look up what rotfl and lol mean
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With respect, looking at the recent posts on the last page, I don't see those used.
In fact, I get the impression you were peeved.
Salty said:
Let me put the descent charging into perspective another way since what seems so obviously foolish to me is not so obvious to others.

You have to slow down your groundspeed to charge. Now, in some aircraft, that isn't an issue if their Vne is low enough, but in many aircraft, that's just wasting time. Time that won't be regained in charging faster (see the next point below)

The amount of charge you can get in 5 or 10 minutes of descent is nothing compared to what you'll get on a 220 volt charger. It wouldn't even be a measurable difference in time to recharge.

It's completely idiotic if you think about it for any amount of time at all. We don't have stop lights and stop signs, and mountains to climb and roll back down over and over again during the trip like you do in a car. In a car you're extending your range with all these micro-charges. But in an aircraft in descent, you aren't extending your range. Your trip is over already. IT DOES NOT MAKE ANY SENSE AT ALL.

And if I have to explain why running a generator off wind power for the entire flight is idiotic, well, I just give up on you.
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Salty said:
I don't have the reference anymore, but I read an article from the Honda engineers that originally worked on their regenerative braking system, and it basically said that it really didn't do much to extend range relative to the extra complexity in the system. I believe the motor / generators are considerably more expensive, and more heavy also? But it's too good a selling point to pass up, and it might help in some corner case trips.
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Salty said:
Do you have people on ignore? or are you just willfully ignoring those that are posting this stuff? I didn't build a straw man, it's been mentioned in this very thread multiple times.
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David Megginson said:
I don't think there's anything to be gained in diving deeper, unfortunately. I try hard to be sensitive about people's feelings in a lot of areas — gender, race, military service, sexual orientation, religious faith, gender identity, disability, socio-economic status, etc — but if people are going to get upset and defensive even when we discuss electric propulsion (or, in other forums, equally-innocuous topics like universal healthcare, firearms registration, etc.), I'm afraid they'll just have to deal with it. We can't walk around on tip-toes over everything.
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Agree. Time will tell who's correct.
 
Cap'n Jack said:
With respect, looking at the recent posts on the last page, I don't see those used.
In fact, I get the impression you were peeved.
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Well, you'd be wrong, perhaps projecting?
 
Cap'n Jack said:
Agree. Time will tell who's correct.
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Given that there are zero people in this thread claiming that personal electric planes will ever (in the most-optimistic projections) make it far past trainer performance, it shouldn't be all that contentious an discussion (or so I would have thought). The only time the idea of an electric plane matching a Bonanza, Comanche, etc for speed/range/load comes up is when someone sets it up as a strawman to shoot down. You could match one of speed/range/load, or maybe (in limited cases) two, but never all three at the same time, because of the absolute chemical limits of batteries.

That's the whole point of the Harbour Air experiment that started the thread. I don't think anyone is foolish enough to think that we could have a battery-powered aircraft with the same speed, range, and load as an ICE-powered Beaver. But since Harbour Air is a very special case (many of their routes are under 30 min, sometimes under 10), they can sacrifice speed and range to get more load in a way that most commercial operations couldn't. Even with that sacrifice, current battery tech won't give them anywhere near the load they need—the surprise isn't that the load and range are so small, but that it flew at all—but it's not theoretically impossible that another generation or two of battery tech could make an electric freight/passenger combo aircraft profitable on those very short-haul routes, even if the useful load is still less than with an ICE (though, TBH, I'd do the experiment with a newer, lighter airframe, not a heavy steel Beaver :) ).
 
Dan Thomas said:
You forget about such things as Angle of Attack on that propeller's blades. In a power-off glide, the AoA is extremely negative, striking the front side of the blade at a steep angle, absolutely the most inefficient way to drive any blade. Further, an ICE keeps the prop turning at idle, reducing that negative AoA; an electric motor would be shut off, making the AoA much steeper and totally useless. The drag of the propeller would steepen the glide so much that you'd have to keep the power on longer in order to reach the airport, negating any gains.

The top figure shows AoA when the prop is producing thrust. Look at the AoA in the bottom picture, a power-off glide. The prop blade's airfoil is flying inverted, and since it's not a symmetrical airfoil, we have a LOT of drag.

56.jpg
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I wasn't claiming that it would be efficient.

I do appreciate the work you put into your explanation, by the way.
 
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Cap'n Jack said:
Me thinks you are reading clickbait. No one seriously will incorporate that into a design. You know- the first and second laws of thermodynamics. The most "efficient" of those ideas is to tap into the tip vortices for recapturing energy. You get more gains in efficiency in greatly reducing vortices.
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How does that "recapture" energy? Energy that's not expended in drag cannot be preserved.
 
3393RP said:
How does that "recapture" energy? Energy that's not expended in drag cannot be preserved.
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When you want to add drag, e.g. on short final and landing, or maybe even when ATC requests an expedited descent, you could add that drag in a way that allows you to recapture a tiny bit of energy, instead by dirtying up the plane with flaps.
 
David Megginson said:
When you want to add drag, e.g. on short final and landing, or maybe even when ATC requests an expedited descent, you could add that drag in a way that allows you to recapture a tiny bit of energy, instead by dirtying up the plane with flaps.
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While the propeller is windmilling? Esoterica has no place in competent engineering.
 
3393RP said:
How does that "recapture" energy? Energy that's not expended in drag cannot be preserved.
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You'll recall that the vortices have a rotation to them. The idea is to put what are described as "turbines" at the wing tip which rotate with the vortices and get energy from the rotation of the air. By taking energy from the vortices, the induced drag is apparently reduced as well, but I didn't bother to look to see how it compared to winglets.
Here's someone's ERAU thesis on the subject: https://commons.erau.edu/cgi/viewcontent.cgi?article=1251&context=db-theses
Here's an abstract in another paper: https://www.semanticscholar.org/pap...rson/2c3b65993d8fb0952305f5e6d4a3e539766ae79b
Another summary from NASA, probably the paper in the link just above: https://ntrs.nasa.gov/citations/19910063991
 
3393RP said:
While the propeller is windmilling? Esoterica has no place in competent engineering.
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It turns out I was "predicting" the past rather than the future. The Pipistrel Alpha already uses the windmilling prop for energy recovery, the same way electric cars use braking.

https://www.numeca.com/pipistrel-re...rical-aircraft-through-propeller-optimization

I was surprised to read that they're seeing a 6% net energy saving that way (I would have guessed right only 1–2%, but the percentage will be lower when battery capacity increases).
 
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David Megginson said:
It turns out I was "predicting" the past rather than the future. The Pipistrel Alpha already uses the windmilling prop for energy recovery, the same way electric cars use braking.

https://www.numeca.com/pipistrel-re...rical-aircraft-through-propeller-optimization

I was surprised to read that they're seeing a 6% net energy saving that way (I would have guessed right only 1–2%, but the percentage will be lower when battery capacity increases).
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You haven't read very carefully. The 6% improvement was in climb performance, and the facts show that 6% has nothing to do with energy recovery.

The baseline propeller was the standard fixed pitch unit used for the piston engine version of the trainer, and the optimized unit's gain of 6% efficiency in climb performance over the other propeller were due to aerodynamic refinements and the addition of controllable pitch over fixed, and unrelated to the energy recovery scheme. Given the fact the EA-002 propeller blades are larger, the pitch is controllable, and the A-SD standard propeller pitch is fixed, the higher efficiency of the EA-002 in climb should come as no surprise.

The touted gains of energy recovery during the descent phase compared to the fixed pitch propeller are due to the larger redesigned blades and adjustable pitch profiles. The EA-002 test was flown at a 35 kt slower descent speed, resulting in a 40% longer descent. The measured energy recuperation of the EA-002 in descent compared to the A-SD was a .14 kWh recapture of power per 100' during the 60 seconds of the test period. They claim a large increase in recuperative ability over the piston engine propeller, but I don't find that compelling.

Cruise performance figures were not provided. Given the increase in blade area, it had to have been affected. Without knowing the overall capabilities of the propeller over the entire operating range of the aircraft, the claims of increased efficiency in the climb and descent are meaningless.

Like many claims and figures surrounding the electrification of transportation, facts have been manipulated or omitted.

In my original post, I almost added "unless a propeller redesign and active pitch control is used", which is obvious. This also goes under the heading of engineering esoterica, because the acquisition and maintenance cost of the propeller along with the increased costs to enable the motor and control components to function in a bi-directional mode is obviously counter to the goal of reducing flight and training costs. In addition, the tests were flown by a test pilot using a predetermined flight profile, which may or may not be valid for real world operations.

Is the cost of acquisition and maintenance of the propeller and bi-directional function less than that of a few kWh introduced by ground charging? We are left to wonder.
 
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Cap'n Jack said:
You'll recall that the vortices have a rotation to them. The idea is to put what are described as "turbines" at the wing tip which rotate with the vortices and get energy from the rotation of the air. By taking energy from the vortices, the induced drag is apparently reduced as well, but I didn't bother to look to see how it compared to winglets.
Here's someone's ERAU thesis on the subject: https://commons.erau.edu/cgi/viewcontent.cgi?article=1251&context=db-theses
Here's an abstract in another paper: https://www.semanticscholar.org/pap...rson/2c3b65993d8fb0952305f5e6d4a3e539766ae79b
Another summary from NASA, probably the paper in the link just above: https://ntrs.nasa.gov/citations/19910063991
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I suggest you read chapters five and six of the thesis.
 
David Megginson said:
Given that there are zero people in this thread claiming that personal electric planes will ever (in the most-optimistic projections) make it far past trainer performance, it shouldn't be all that contentious an discussion (or so I would have thought). The only time the idea of an electric plane matching a Bonanza, Comanche, etc for speed/range/load comes up is when someone sets it up as a strawman to shoot down. You could match one of speed/range/load, or maybe (in limited cases) two, but never all three at the same time, because of the absolute chemical limits of batteries.

That's the whole point of the Harbour Air experiment that started the thread. I don't think anyone is foolish enough to think that we could have a battery-powered aircraft with the same speed, range, and load as an ICE-powered Beaver. But since Harbour Air is a very special case (many of their routes are under 30 min, sometimes under 10), they can sacrifice speed and range to get more load in a way that most commercial operations couldn't. Even with that sacrifice, current battery tech won't give them anywhere near the load they need—the surprise isn't that the load and range are so small, but that it flew at all—but it's not theoretically impossible that another generation or two of battery tech could make an electric freight/passenger combo aircraft profitable on those very short-haul routes, even if the useful load is still less than with an ICE (though, TBH, I'd do the experiment with a newer, lighter airframe, not a heavy steel Beaver :) ).
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Once again, Harbour Air has claimed they are going to electrify their fleet of DHC-2s.
 
3393RP said:
I suggest you read chapters five and six of the thesis.
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Why should I?
I was merely explaining how some energy could be captured from the vortices in response to your post:
3393RP said:
How does that "recapture" energy? Energy that's not expended in drag cannot be preserved.
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I answered your question and gave you 2 or 3 references. My personal opinion is that there is more gains in efficiency in reducing the vortices from the start, rather than recovering energy from them.
 
David Megginson said:
When you want to add drag, e.g. on short final and landing, or maybe even when ATC requests an expedited descent, you could add that drag in a way that allows you to recapture a tiny bit of energy, instead by dirtying up the plane with flaps.
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Flaps lower the stall speed, therefore the touchdown speed, making the landing shorter and safer. The drag of a windmilling prop does nothing for touchdown speeds.

Feathering the prop would be the best way to gain efficiency in a glide. It would allow a longer, shallower descent path at zero power, conserving battery power rather than sacrificing altitude to gain very small recharging. The number quoted in post 178 says that .140 kWh was gained per 100 feet of altitude loss; that's 140 watts per 100 feet, or 0.188 horsepower' worth of power for the same time it descends that 100 feet. Before efficiency losses, yet. That seems laughable to me, compared to a feathered prop and much shallower descent.

Someone good at physics could calculate the horsepower required to climb a 2000-pound airplane 100 feet. It would be a LOT more than 140 watts/.188 HP.
 
Cap'n Jack said:
Why should I?
I was merely explaining how some energy could be captured from the vortices in response to your post:
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Because you would have learned the thesis concluded that your statement "...By taking energy from the vortices, the induced drag is apparently reduced as well..." is incorrect.
 
Dan Thomas said:
Flaps lower the stall speed, therefore the touchdown speed, making the landing shorter and safer. The drag of a windmilling prop does nothing for touchdown speeds.

Feathering the prop would be the best way to gain efficiency in a glide. It would allow a longer, shallower descent path at zero power, conserving battery power rather than sacrificing altitude to gain very small recharging. The number quoted in post 178 says that .140 kWh was gained per 100 feet of altitude loss; that's 140 watts per 100 feet, or 0.188 horsepower' worth of power for the same time it descends that 100 feet. Before efficiency losses, yet. That seems laughable to me, compared to a feathered prop and much shallower descent.

Someone good at physics could calculate the horsepower required to climb a 2000-pound airplane 100 feet. It would be a LOT more than 140 watts/.188 HP.
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No, a 2000 pound object can be raised 100 feet with 0.188 hp. Look up the definition of horsepower.
 
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3393RP said:
Because you would have learned the thesis concluded that your statement "...By taking energy from the vortices, the induced drag is apparently reduced as well..." is incorrect.
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Look at the other references. They were written after the thesis.
The turbine, driven by the vortex flow, reduces the strength of the vortex, resulting in an associated induced drag reduction.
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Just what are you getting at? I never said it was a great idea- here's my post again that started your line of questioning:
Cap'n Jack said:
The most "efficient" of those ideas is to tap into the tip vortices for recapturing energy. You get more gains in efficiency in greatly reducing vortices.
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Tantalum said:
https://www.autoevolution.com/news/...ions-by-95-mit-says-it-could-work-155366.html

Sounds safe. Just 0.6% more gas required... to pollute less..
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Reading their treatise reveals it also requires a large increase in airliner L/D ratio, the adoption of small core turbofans with less than half the thrust of current engines, and blowing engine exhaust through a catalyst device.

I didn't see any estimate of the weight the gas turbine, catalyst assembly, storage tank and urea fluid for particulate capture, electrical generator, wiring, and electric motors that will replace the propulsion turbines of the aircraft. Given that and the efficiency loss in converting jet fuel to electric power to thrust, I'm more than a little skeptical about the claimed less than 1% increase in fuel burn. Of course, greatly increasing the aerodynamic efficiency of the airframe may be of great benefit. How that will be accomplished isn't addressed.

Other than that, they have solved the problem of aviation NOX emissions.
 
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3393RP said:
Reading their treatise reveals it also requires a large increase in airliner L/D ratio, the adoption of small core turbofans with less than half the thrust of current engines, and blowing engine exhaust through a catalyst device.
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Why would they use a turbofan for this? Just use a gas turbine like those used for electrical generation now. A fan isn't useful when used as described in the abstract:
Due to its size, any SCR system will likely need to be housed in the aircraft body, potentially making it most suitable for future hybrid- or turbo-electric aircraft designs.
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3393RP said:
I didn't see any estimate of the weight the gas turbine, catalyst assembly, storage tank and urea fluid for particulate capture, electrical generator, wiring, and electric motors that will replace the propulsion turbines of the aircraft. Given that and the efficiency loss in converting jet fuel to electric power to thrust, I'm more than a little skeptical about the claimed less than 1% increase in fuel burn. Of course, greatly increasing the aerodynamic efficiency of the airframe may be of great benefit. How that will be accomplished isn't addressed.

Other than that, they have solved the problem of aviation NOX emissions.
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I'm not sure they have thought it completely through. It's in interesting starting point.
 
3393RP said:
Reading their treatise reveals it also requires a large increase in airliner L/D ratio, the adoption of small core turbofans with less than half the thrust of current engines, and blowing engine exhaust through a catalyst device.

I didn't see any estimate of the weight the gas turbine, catalyst assembly, storage tank and urea fluid for particulate capture, electrical generator, wiring, and electric motors that will replace the propulsion turbines of the aircraft. Given that and the efficiency loss in converting jet fuel to electric power to thrust, I'm more than a little skeptical about the claimed less than 1% increase in fuel burn. Of course, greatly increasing the aerodynamic efficiency of the airframe may be of great benefit. How that will be accomplished isn't addressed.

Other than that, they have solved the problem of aviation NOX emissions.
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Kind of reminds me of the VW (and others) EPA scandal where they rigged the ECU to meet the parameters of the EPA test even though the vehicle ran cleaner overall in real world operation with their non-EPA programming. But hey NOx emissions were lower on the EPA-programming when at idle, lol. Or ethanol fuel that is "better for environment" because it burns fewer hydrocarbons yet results in lower fuel mileage causing the burning of additional hydrocarbons . . .
 
jsstevens said:
I ran across this today (saw it on slashdot initially). A pump-able paste with "10x the energy density of current batteries". If it's real it could be a game changer:
https://www.fraunhofer.de/en/press/...1/hydrogen-powered-drives-for-e-scooters.html
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Why bother converting to electricity in a fuel cell? This seems like a waste, just burn it. H2O is the waste product, along with heat and mechanical energy. Likely much more efficient than fuel cells which also require rare earth elements.

Tim
 
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