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Electric Islander

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Electric Islander

Old 18th Oct 2018, 13:52
  #21 (permalink)  
 
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Originally Posted by msbbarratt View Post
A lot of these downsides go away or become irrelevant if you consider the electricity to be free (solar, wind, etc). One way or another we seem to be heading kinda in that direction, but it's a long way from free still.
No, we're not heading in that direction, nor will we ever be. Any meaningful measure of the cost of electricity will include the cost of the investment in generation equipment and the operation costs. That isn't ever going to be free.
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Old 18th Oct 2018, 13:55
  #22 (permalink)  
 
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Originally Posted by krismiler View Post
Possibly some energy could be returned to the batteries by windmilling propellors on the descent in the same way electric vehicles can recharge their batteries by using the motor as a brake.
I doubt that those aircraft spend any significant portion of their flights at a power setting low enough that the air is driving the props. Maybe a few seconds as the airplane is in the landing flare.
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Old 18th Oct 2018, 14:14
  #23 (permalink)  
 
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Originally Posted by Chris Scott View Post
Yes. Unless they employed very clever technology, the props on the electric one would be nearly as noisy.
It would be theoretically possible to make the props considerably quieter. Props on direct drive piston engines are noisy in large part because they're frequently operating with the prop tips in the transonic range. With electric motors you could have slower turning props, which would be quieter, much like the prop on a PT-6 powered plane is quieter than a less powerful, direct drive piston powerplant.
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Old 18th Oct 2018, 14:18
  #24 (permalink)  
 
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Originally Posted by DaveReidUK View Post
One way around that would be a quick-change battery module so that they don't have to be recharged in situ.
There was such an experimental road vehicle some years ago, an electric (normal) bus which towed a trailer with the batteries in it, which was swapped every couple of hours for another when the vehicle passed the charging base. Like most other such initiatives, it seems not to have worked out.
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Old 18th Oct 2018, 14:55
  #25 (permalink)  
 
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Originally Posted by Gargleblaster View Post
Regarding this type, this is one of the funniest posts I've read in here: Britten Norman Islander
Back in the 1970s I was a schoolboy in what was then called Rhodesia and is now Zimbabwe. For reasons that escape me I was offered the opportunity to fly from Bulawayo to a mine in the bush about 45 minutes' flight away. There were, IIRC, 6 of us in a BN Islander and, unusually, there was low cloud across the country. In addition, there was a certain degree of terrorist/freedom fighter activity in the area. Consequently we flew low level there and back, ducking in and out of the valleys and around the hills on the basis that before they heard us coming we would have gone. If the Islander was as tough to fly as your pointer implies, I'd guess the flight must have been a great workout for the pilot ...

I'll never forget that flight. It was spectacular.
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Old 18th Oct 2018, 16:58
  #26 (permalink)  
 
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I wonder if this could be for the isles of Scilly route?
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Old 18th Oct 2018, 17:03
  #27 (permalink)  
 
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Originally Posted by rog747 View Post
I wonder if this could be for the isles of Scilly route?
See first post: Orkney islands could get first electric plane service
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Old 18th Oct 2018, 17:08
  #28 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Thanks Dave, I had a reread - I think the Lands End - St Marys maybe stretching the tech electrickery just a tad for now?
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Old 18th Oct 2018, 17:19
  #29 (permalink)  
 
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Originally Posted by krismiler View Post
Possibly some energy could be returned to the batteries by windmilling propellors on the descent in the same way electric vehicles can recharge their batteries by using the motor as a brake.

Electric cars can recharge to around 80% very quickly, it's the last few percent which takes time to trickle in.
Yet another conceptual mistake, such as you find everywhere in the green madness of todays world!

A car driver that approaches a red traffic light at 50 mph and then brakes to stop the car is wasting the kinetic energy that is in the car - he should have started coasting early enough to come to a stop right at the traffic light without any braking. Because this method is impractical in normal traffic, hey, an electric car can use the motor as a generator to convert the kinetic energy back to stored electric power in the battery.

An airplane that descends from cruise level to landing does use the coast technique already, the engines are already just idling, it cannot be done more efficiently. If you want to “brake” by using the propellor to drive the e-motor as a generator, your aircraft will have more drag, thus descend more steeply than the idle glide path. You will have to expend (=waste) energy either before starting descent, by staying level longer, or by flying level at the bottom of the descent.

There is no such thing as a free lunch!
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Old 18th Oct 2018, 20:42
  #30 (permalink)  
 
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Originally Posted by WHBM View Post
There was such an experimental road vehicle some years ago, an electric (normal) bus which towed a trailer with the batteries in it, which was swapped every couple of hours for another when the vehicle passed the charging base. Like most other such initiatives, it seems not to have worked out.
Toyota announced earlier this year a lithium ion battery technology with a solid electrolyte. Because of this the battery can be deeply cycled, rapidly charged, and generally abused a lot more, because the electrolyte keeps everything in its place. They were talking about 5 minutes charge times for cars, coming to a forecourt near you sometime in 2023.

If that's really true, this is going to be close to the peak performance theoretically achievable with lithium ion chemistries. It still won't be as good as petrol in energy per kg or volume, but the nicer characteristics will make them far more useable. No need to swap out the battery, just fill it like you would any other fuel tank.
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Old 18th Oct 2018, 21:17
  #31 (permalink)  
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Old 18th Oct 2018, 21:22
  #32 (permalink)  
 
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Originally Posted by stalling attitude View Post
I think the Orkneys are quite close together. Could just use a long mains extension lead from Kirkwall instead of mucking about recharging batteries
Papa Westray is about as far from KOI as St Mary's (see above) is from Land's End, though admittedly there are more dry bits en route for when the batteries fail unexpectedly.
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Old 18th Oct 2018, 22:24
  #33 (permalink)  
 
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Originally Posted by msbbarratt View Post
A lot of these downsides go away or become irrelevant if you consider the electricity to be free (solar, wind, etc). One way or another we seem to be heading kinda in that direction, but it's a long way from free still.
Oil is just there under the ground, it is as "free" as solar or wind. People have managed to take "ownership" of it and charge for it, but that is an artificial concept, Costs for capital plant and operating costs for extracting, processing and distributing to point of use apply to all forms.
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Old 18th Oct 2018, 22:25
  #34 (permalink)  
 
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They were talking about 5 minutes charge times for cars
By my quick arithmetic, that means a charge current of over 1000A. If the total circuit resistance is just 1 milliohm, that implies a loss of 1 KW. They would need superconducting cables to carry that kind of current without substantial resistive losses. I can just see the average gas/petrol station dealing with liquid helium...
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Old 18th Oct 2018, 22:33
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why not use a boat?
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Old 18th Oct 2018, 22:37
  #36 (permalink)  
 
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Originally Posted by WHBM View Post
Oil is just there under the ground, it is as "free" as solar or wind. People have managed to take "ownership" of it and charge for it, but that is an artificial concept, Costs for capital plant and operating costs for extracting, processing and distributing to point of use apply to all forms.
👏🏼👏🏼👏🏼 Very well said Sir.

Best of luck to the Electric Islander PR stunt crew. Remember, anything is possible if you throw enough cash at it......
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Old 18th Oct 2018, 23:17
  #37 (permalink)  
 
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The propeller tips of an Islander sit only a few inches from the ears of the pilot and front seat passenger, where as most light twins are low wing and the few feet of difference in engine position has a huge effect on interior noise levels.

Can anyone comment on the noise of the turbine version ?
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Old 19th Oct 2018, 06:32
  #38 (permalink)  
 
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I wonder what the flight planning is for fuel Lands End to St Mary's?

We know the weather can be and/or go dodgy at both ends -

If they cannot get in at St Mary's do they plan for returning to Land Ends, plus a hold then diversion fuel to say NQY if Lands End goes out?

Probably would stretch an electric BN islander - but a most interesting concept
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Old 19th Oct 2018, 08:15
  #39 (permalink)  
 
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Originally Posted by lbhsbz View Post
why not use a boat?
In Orkney and Shetland - where this is I think being initially contemplated, the coastlines and waters can be quite treacherous - and routings extremely slow.

I've done Kirkwall to Westray by boat, for example, a commercial service, weaving in and out of tiny little rocky islands - it takes about 90 minutes, and I'm guessing (I'm no sailor) that regularly there are surface conditions that make that very ill advised.

The total distance is about 20nm! So even in an Islander, under 10 minutes - and whilst clearly some conditions, such as heavy fog would be as problematic as for a ship, many other conditions would be fine for the aeroplane but not the boat.

The air ferry around those two groups of islands is most definitely essential to maintaining a decent quality of life for the people who live there.

G
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Old 19th Oct 2018, 11:04
  #40 (permalink)  
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One way around that would be a quick-change battery module so that they don't have to be recharged in situ.
For our 172 project, we discussed this in great detail. There are three practical options for battery location in a 172, and by extension, probably an Islander too: In the wing fuel tank area - great location for best utilization of space, but also the very most difficult place to rapidly swap out batteries. In the cabin, easier to access, and perhaps swap, though handling a many hundred pound load will require a forklift, which will invariably end up accidentally damaging the airframe at some point. This location will use up valuable cabin volume at the C of G, and could be a hazard to occupants. And, my idea was a removable belly pack. Again, it must be at the C of G, and would require a very robust latching mechanism, so lots of airframe mods to carry those loads. The aircraft also has to have adequate ground clearance. But, like changing weapons, it could be done quickly, with the lease risk of airframe damage. All of these were considered major operational obstacles.
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