Electric Islander

[pzu]

https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-45876604

PZU - Out of Africa (Retired)

[Herod]

It makes sense to introduce an electric aircraft on the routes around the Orkneys. A big difference between the short hops with a small aircraft and trying a 737 size on longer routes. My guess is it will work.

[Chris Scott]

So a two-minute sector (or perhaps a couple) followed by how long a recharging period?

PS: Is this thread restricted to septuagenarians? :eek:

[n5296s]

I don't understand how this will work. I thought the Islander was powered by the noise the engines make?

(And no, not quite there yet myself, a few years to go).

[treadigraph]

It makes sense to introduce an electric aircraft on the routes around the Orkneys. A big difference between the short hops with a small aircraft and trying a 737 size on longer routes. My guess is it will work.
We won't charge you if you're wrong...😊

[ion_berkley]

So a two-minute sector (or perhaps a couple) followed by how long a recharging period?

PS: Is this thread restricted to septuagenarians? :eek:

Serious back of the envelope calculation here with a little real world data thrown in:

Islander with 2x 300HP engines = approx 400kW peak power output

Lets assume that the whole 2 min sector is flown at full power to be nice and pessimistic...so 13.3kWh per sector.

Now the complete battery assembly for the Tesla Model3 is pretty representative of the bleeding edge of EV battery technology and it comes in at 168Wh/Kg.
The total mass of the ~75kWh battery pack in a Model3 is approx 470 Kg. Empirically I can tell you that my Model3 charges from say 20% to 80% in about 40 minutes from a DC fast charger.

That passes the smell test for me, it seems very practical for this particularly odd air route.

[pattern_is_full]

Yes, the Islander is a pretty flexible little test-bed. There have been ducted-fan, turboprop and 3-engine mods. And minimal systems power-&-complexity overhead required: no pressurization, retractable gear, spoilers, or such.

[msbbarratt]

I don't understand how this will work. I thought the Islander was powered by the noise the engines make?

(And no, not quite there yet myself, a few years to go).

The noise doesn't come from the engines, their cores are far too small to make that din.

[msbbarratt]

Serious back of the envelope calculation here with a little real world data thrown in:

Islander with 2x 300HP engines = approx 400kW peak power output

Lets assume that the whole 2 min sector is flown at full power to be nice and pessimistic...so 13.3kWh per sector.

Now the complete battery assembly for the Tesla Model3 is pretty representative of the bleeding edge of EV battery technology and it comes in at 168Wh/Kg.
The total mass of the ~75kWh battery pack in a Model3 is approx 470 Kg. Empirically I can tell you that my Model3 charges from say 20% to 80% in about 40 minutes from a DC fast charger.

That passes the smell test for me, it seems very practical for this particularly odd air route.

There are some downsides. The battery is heavier than the equivalent fuel tank. The power cables are heavier than the equivalent fuel lines. The motors are heavier than the equivalent gas turbines, and can't sustain max power for as long either (efficiency in a motor conflicts with cooling it with air). The batteries don't get lighter as they discharge. Charging times are longer than refueling times (but maybe irrelevant given other operational factors).

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.

[Espada III]

Charging also available from wing and fuselage covering of solar cells. This would have a modest but not negligible benefit on range and charging times.

[Capt Fathom]

I thought the Islander was powered by the noise the engines make?

Electric Engines!
​​​​​​​Who would have thought the day would come when an Islander could sneak up on you!

[krismiler]

The 300hp version had fuel injection, there was also a 265hp carburettor varient.

​​​​​​The route could be a proving ground for trying out the new technology which could find its way into simple single engine types.

Obviously at the moment it's not a viable replacement for piston engines though.

[scifi]

Just one question, how would you fly it out to the Islands from the Mainland, if you require 30 minutes reserve capacity..?

edit... Would their nearest engineering base be Aberdeen, to do the initial installation..?

[EDLB]

With 30min VFR or 45min IFR reserve it will become an interesting calculation. Possible, Yes but economic?

[scifi]

Just another snag.... How many airfields have the right PLUG...?

[Pilot DAR]

I was hired to investigate the design and design compliance of a proposed STC modification of a 172 from Lycoming engine to electric motor. Though achievable, the major commercial obstacle was the loss of use of the aircraft while the batteries were recharged - fly it for 45 minutes, and it then sits for many hours recharging. Not good utility, though it seems like this operation has a better than normal opportunity.

For commercial operation, the modification will have to be STC approved (to maintain a C of A). A challenge is that the present basis of certification of the aircraft (and for STC) contains a lot of design standards which would exclude electric motors as powerplants. This should and will change, though a lot of regulatory changes will be needed, and those don't happen quickly.

Electric planes will become practical for some roles, but in the mean time, some battery advancement is still needed. We'll get there on day, and everyone who is trying, is helping.

[Chris Scott]

The noise doesn't come from the engines, their cores are far too small to make that din.

Yes. Unless they employed very clever technology, the props on the electric one would be nearly as noisy. Would they be constant-speed and fully-feathering, or would either of those features be unnecessary?

Unless the aircraft could continue to do the leg to Kirkwall, which seems unlikely with current battery technology, Loganair must be contemplating creating records for lowest average aircraft utilisation per day.

"Hello Madam, welcome to Papa Westray. I hope you enjoyed your noisy flight from Kirkwall. If you wish to continue your journey, please gather your personal items together and accompany me to our quiet, environmentally-friendly, Whispering Dwarf aircraft for the short hop to Westray...." :rolleyes:

[DaveReidUK]

Though achievable, the major commercial obstacle was the loss of use of the aircraft while the batteries were recharged - fly it for 45 minutes, and it then sits for many hours recharging.

One way around that would be a quick-change battery module so that they don't have to be recharged in situ.

[krismiler]

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.

[Gargleblaster]

Regarding this type, this is one of the funniest posts I've read in here: https://www.pprune.org/tech-log/436319-britten-norman-islander.html#post6118466

[A Squared]

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.

[A Squared]

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.

[A Squared]

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.

[WHBM]

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.

[msjh]

Regarding this type, this is one of the funniest posts I've read in here: https://www.pprune.org/tech-log/436319-britten-norman-islander.html#post6118466

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.

[rog747]

I wonder if this could be for the isles of Scilly route?

[DaveReidUK]

I wonder if this could be for the isles of Scilly route?

See first post: Orkney islands could get first electric plane service (https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-45876604)

[rog747]

See first post: Orkney islands could get first electric plane service (https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-45876604)

Thanks Dave, I had a reread - I think the Lands End - St Marys maybe stretching the tech electrickery just a tad for now?

[EMIT]

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!

[msbbarratt]

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.

[pzu]

https://www.pressandjournal.co.uk/fp/news/islands/orkney/1587352/island-electric-plane-service-to-cost-10m/

PZU - Out of Africa (Retired)

[DaveReidUK]

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.

[WHBM]

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.

[n5296s]

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...

[lbhsbz]

why not use a boat?

[Switchbait]

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......

[krismiler]

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 ?

[rog747]

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

[Genghis the Engineer]

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

[Pilot DAR]

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.

[scottish_aviator]

Serious back of the envelope calculation here with a little real world data thrown in:

Islander with 2x 300HP engines = approx 400kW peak power output

Lets assume that the whole 2 min sector is flown at full power to be nice and pessimistic...so 13.3kWh per sector.

Now the complete battery assembly for the Tesla Model3 is pretty representative of the bleeding edge of EV battery technology and it comes in at 168Wh/Kg.
The total mass of the ~75kWh battery pack in a Model3 is approx 470 Kg. Empirically I can tell you that my Model3 charges from say 20% to 80% in about 40 minutes from a DC fast charger.

That passes the smell test for me, it seems very practical for this particularly odd air route.

The math is a little bit out on this one, it's actually better than you calc

300hp = 223 kw, not 400. Also the Loganair BN2s are carb so only 265hp, meaning 197kw.

Assume one of the longer legs, say 15 minutes. You would fly 1 min @ full power, 13 mins @ 75% and 1 min @ 50%. This equates to 14.8kwhr. You could satisfy this + 30 mins reserve with a 50kwhr battery pack, using tesla math is ~300kg.

Very achievable!

Hot swap battery packs on turnaround and charge them while they're not on the aircraft. Keep those sub 5 minute turnarounds going

[DaveReidUK]

300hp = 223 kw, not 400. Also the Loganair BN2s are carb so only 265hp, meaning 197kw.

I think you'll find the poster's 400 kW was for two engines (446 kW rounded down).

Yours (197 kW x 2) comes to 394 kW, so we're splitting hairs here.

[scottish_aviator]

I think you'll find the poster's 400 kW was for two engines (446 kW rounded down).

Yours (197 kW x 2) comes to 394 kW, so we're splitting hairs here.

My bad! I also completely mucked up the calculation, the 15 minute trip would actually require 73.875 kwhr and 30 mins reserve would be 194 kwhr, giving total weight of ~1200kg which is definitely prohibitive.

[DaveReidUK]

My bad! I also completely mucked up the calculation, the 15 minute trip would actually require 73.875 kwhr and 30 mins reserve would be 194 kwhr, giving total weight of ~1200kg which is definitely prohibitive.

We'll let you off.

James Watt will probably forgive you too (by convention, SI units named after real people get a capital letter).

:O

[horizon flyer]

Once batteries hit approx. 3kw per kg then they can replace avgas/petrol even though avgas is approx.12kw/kg IC engines are only 25% efficient and electric motors are 90% approx. Lithium air batteries have in theory 11kw/kg max but difficult to achieve but could make 2.5kw/kg which would be close. So far Li air have only lasted a few recharge cycles on air and needs pure oxygen to last, so not practical but a total rethink by a university research group in the US, with help from a super computer group have come up with one that has lasted 750 recharge cycles and can run directly on air, so the holy grail of batteries may be in sight so I believe recharge time will be critical, not the weight for commercial operation.

[ion_berkley]

My bad! I also completely mucked up the calculation, the 15 minute trip would actually require 73.875 kwhr and 30 mins reserve would be 194 kwhr, giving total weight of ~1200kg which is definitely prohibitive.

OK let's run a little farther with the numbers to test this out some more with a practical configuration.
Seems like 200Liters of fuel is about all you can take with a maximum revenue load out on the conventional Islander so what battery mass would that give us?
Dry weight of an IO-540 is 200Kg. Dry weight of a Siemens SP260D (230kW+ rated) is 50Kg...so *2 (and wildly assuming similar mass add for props/coolant/lube/ancillaries etc) we save 2*150Kg=300Kg on our electric converted Islander, so we get that mass of battery for free to reach the ZFW of a conventional Islander, then another ~160Kg of battery to approximate the mass of 200 liters of fuel and reach MTOW.
Using my original Tesla based 168Wh/Kg number, thats 460*168=77kWh of battery, which doesn't sound close to viable if we assume 75% power for the hold and a conventional VFR reserve.

Will be interesting to see if this is something that the CAA will be willing to get engaged into to starting thinking through operational and regulatory issues associated with electric and hybrid commercial flight.

(All numbers from the internet, no POH data...your milage may vary etc etc!)


FWIW, for those who like to nerd out:
Siemens (incl SP260D) presentation
https://nari.arc.nasa.gov/sites/default/files/attachments/Korbinian-TVFW-Aug2015.pdf

Pipistrel Alpha-Electro - Series production electric aircraft designed around a specific mission with some certification success. Answers some questions about what a modern slippery composite airframe can achieve and also datapoint on in-flight regen and noise.
https://www.pipistrel.si/plane/alpha-electro/overview

[A Squared]

Once batteries hit approx. 3kw per kg then they can replace avgas/petrol even though avgas is approx.12kw/kg

Kw/kg is meaningless gibberish when speaking of a liquid fuel.

[DaveReidUK]

Kw/kg is meaningless gibberish when speaking of a liquid fuel.

And kW/h is equally meaningless when talking about batteries ...

[A Squared]

And kW/h is equally meaningless when talking about batteries ...

Well, actually, KW/hr is meaningless in any context.

[peterperfect]

solar panels = no night flying = win !

[DaveReidUK]

Well, actually, KW/hr is meaningless in any context.

Well if we're going to be pedantic, let's do it properly. :O

KW/hr (more correctly kW/h) is a measure of the rate of change of energy consumption, so I'd be willing to bet that it's a quantity that makes sense to the power distribution companies.

[Loose rivets]

Redesign the Islander so that it's really clean and pointy. Mag-lev it down the runway and up a ramp, both of which point at the destination. At some point c 3,000' with runway in sight, flick the engine's two big toggle switches to the ON position . . . preferably at the same instant.

As with all forms of transport - not needing the power in the first place is the best route to economy.

[WingNut60]

Don't omit or underestimate the weight of required control gear.
These are not ancillaries, they are just as important as the motor and batteries and they tend to be weighty.

Me? I'd be looking to a hybrid as a practical solution in the short term.
Either electric augmented by a smaller engine or vice versa.
In either case I'd pick a single (Caravan?) and not a twin.
Shorter cable runs and no need for duplication.
Motor rotor built into the prop drive shaft passing through stator.
Regen on descent - maybe obviate the need for flaps?

Lotsa possibilities.

[Eutychus]

Regarding this type, this is one of the funniest posts I've read in here: https://www.pprune.org/tech-log/436319-britten-norman-islander.html#post6118466

I skim-read that post yesterday, having flown fairly often in Trislanders, found it hilarious, went back to enjoy it, and now it seems to have disappeared?

[DaveReidUK]

I skim-read that post yesterday, having flown fairly often in Trislanders, found it hilarious, went back to enjoy it, and now it seems to have disappeared?

Try clearing your browser cache - it's definitely (and happily) still there.

[A Squared]

Well if we're going to be pedantic, let's do it properly. :O

KW/hr (more correctly kW/h) is a measure of the rate of change of energy consumption, so I'd be willing to bet that it's a quantity that makes sense to the power distribution companies.

I will have to concede that you have identified a narrow application where kW/h may not be gibberish. Beyond that though ....

[Chu Chu]

Electric motors (at least when fitted with a sufficient mass of control gear ;)) can operate efficiently at a broader range of RPMs than can most combustion engines. I wonder if that characteristic could be use to help mitigate propeller noise (e.g. operating a a somewhat lower RPM and higher pitch at low speeds).

[scifi]

To be even more pedantic, the unit is kWhr.
But as you will get the same result multiplying by 1, as dividing by 1. I suppose it makes no difference.
.

[A Squared]

To be even more pedantic, the unit is kWhr.
But as you will get the same result multiplying by 1, as dividing by 1. I suppose it makes no difference.
.

Ummm, no, kW/hr is something completely different than kWhr

[DaveReidUK]

Glad we've got that settled. :O

[KiloB]

Sorry guys, but until their is a MAJOR tech breakthrough electric aircraft can be catagorised with chocolate teapots.

A case can be made for hybrids, but not pure electric.

[SandyYoung]

I wondered how long it would take before the voice of reason was heard. We are in a time of 'electric mania' but it will pass and something else will excite us.

[n5296s]

A case can be made for hybrids
Go on then...? Hybrid makes a lot of sense for road transport - most of the time only a fraction of the engine's total power is in use, plus you can recycle energy from braking. So you can have a much smaller engine, supplemented with an electric motor and a small battery. But for flying? The engines typically run at around 75% full power for hours and hours, so where do the energy savings apply?

[CRayner]

I think we need more blue sky thinking here. Much of the power is consumed accelerating to rotation. So, a pair of steel main wheels with a longitudinally divided runway, positive on left, neg on right, possibly tricky in a crosswind, but a bit of pilot training should sort that. Then in case of unplanned flight diversion etc. a converted tanker with an enormous battery and a couple of heavy gauge dangling power leads for in flight recharging. Perhaps this could all be augmented by a massive elastic catapult.

[DaveReidUK]

Sorry guys, but until there is a MAJOR tech breakthrough ...

Didn't they say something similar about Wilbur and Orville? They weren't saying it for long.

[Random SLF]

Didn't they say something similar about Wilbur and Orville?

Distant relatives of mine (I'm a Wright too) but we don't like to shout about it. EV manufacturers desperately need the kudos of an actual electric-powered scheduled flight - it'd be publicity gold. I really hope it works.