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Electric Aircraft Propulsion 1

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Next logical step is to use the battery as wing structure.
Maybe four packages that look like the forward or after portion of port or starboard wings, all bolted to a generally planar spar/busbar.

Details are left for the reader...



Mike Halloran
Corinth, NY, USA
 
^I think the opposite. That way it's easy to remove/repair/exchange battery modules to turn the a/c around.
 
The original fuel tanks held 332 US Gallons, and a very well packaged Lithium battery might fit 4000 pounds in that space and carry 400 kWhr. That gets you a 1/2 hour flight but still blows your weight budget.
Click to expand...

And, how much flight did the 332 gallons of fuel amount to? Something like 1070 nautical miles? 1/2 hour flight time is barely 90 nautical miles of range. Landing every 1/2 hr to swap batteries seems to be a bit dubious; like the Pony Express, but batteries instead of horses. That's a lot of infrastructure to support.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
zeppelins anyone ?

another day in paradise, or is paradise one day closer ?
 
Aviation always has been, and always will be, about lightness. Next.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
 
Normally, it can do 180 knots for 5 hours, which carries it about 900 nautical miles (1600 km).
The 1/2 hour flight would only get it 90 miles.
Being from Canada myself, the first thing that makes me think of is that there are a lot of airports here that DON'T have another (paved, long enough) airport within 90 miles.
Harbour Air can get away with it because some of their island-hops really are that short.


 
Hybrid electric with exceptionally efficient turbogenerators… or with exceptionally efficient turboprops...

I think that GA turbine technologies may be evolving fast, under the radar.

The following article came thru a link in an SAE newsletter... an [experimental/evolving] family of small turbine engines with highly evolved internal flow technology for major increases in power/fuel efficiencies.

One version shown is as a classic [tractor or pusher?] 'turboprop' arrangement... engine-to-drive-shaft-to-gearbox-to-prop. Another version is shown as a turbogenerator that could be installed at any remote [buried?] location in the airframe... and could provide in-flight [recharging] power for electric propulsion systems. Not now... but in todays fast evolving world... probably 'soon'.

Bringing Turbine Power to Small Aircraft
TURBOTECH designs, develops and manufactures innovative regenerative turbines & propulsion systems. Combining proprietary heat-exchangers with state-of-the-art turbines, TURBOTECH's recuperated turbines power conventional and innovative aircraft architectures.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
 
the electricity generator (aka turbine/turbo engine) can be co-located with the motor (driving the propeller) or not. Trade-offs may be W&B, reduced nacelle size, weight of copper wiring, etc

another day in paradise, or is paradise one day closer ?
 
Turbogenerators do allow configurations that are not possible or practical otherwise, rotordynes (replacing the ram jets with an unducted fan should greatly improve the noise issue)and the X-57 (basically a completely blown wing without flaps or slats) would be examples of these configurations.
 
Any equipment interposed between the prime mover and the propeller/fan will have to "buy" its way on board. New failure modes will be incremental to existing ones. Maybe the ability to re-route power around a point of failure would partially mitigate the failure severity. Might be wise anyway to default to a direct mechanical connection in the event of failure. Batteries will not offset liquid hydrocarbon fuel storage by their own virtue, since their relative energy storage capacity per unit mass is atrocious by comparison (see above).
Should benchmark an alternative system whereby a purpose-designed multi-engine craft with conventional propulsion shuts down one or more engines for cruise, in order to operate at optimum efficiency. This has been done in the past with military patrol types, though normally for maximum endurance operations, not necessarily maximum range.
Back in the day there was a version of the Hawker Siddeley Trident with an oversize APU that was used to augment take-off thrust, then shut down for the remainder of the flight, if I'm not mistaken. Similar concept arrived at from a different direction. (It's not broken, it's British! [lol])


"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
 
Turbotech. Wow... I just saw the future.
I want one in my RV8!
 
RS... currently in production... close-to right sized for RV8... pricey...

PBS-TP100

BTW, when I was the lead USAF engineer for Cessna O-2... I was shown photos/data on the prototype O-2TT... replaced the [2] small continental 6-bangers with [2] de-rated Allison turbines. A shame that it was never developed.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
 
Pipistrel remains determined:


Pipistrel's E-811 engine produces 57.6 kW of maximum take-off power and drives a three-blade fixed-pitch prop on the Velis Electro. The aircraft has an MTOW of 600 kg, a BEW of 428 kg, a cruise speed of 90 KCAS at 35 kW and an endurance of 50 mins plus VFR reserve.
Click to expand...

Additional data in the type certificate:

This is a light-sport aircraft, of course. Not something to compete with a FAR/CS 23 normal category aircraft, and not equipped to handle anything but the simplest of flying in the gentlest of weather. It's just a start...

Anyway, they managed to get a 57kW motor and 22kWhr of batteries into a 440kg empty weight. I do wonder what it sounds like to hear the prop but not hear an engine.

 
I had mentioned in an earlier post that Pipistrelle had done this. The flight profile is one hour of instruction or solo practice, followed by landing, taxi back to FBO then a battery change out. Fully charged batteries are on standby for the next student, or lesson whatever.
B.E.

You are judged not by what you know, but by what you can do.
 
Hi Folks,

Couple comments to Will's posts.
Small turboprops - PBS engine is quesi-virtual product, i've investigated this little bit and information received from PBS is they will not going to certify this (all application for thi are falling in Experimental category). Generally turboprop engine of this size it is real gas guzzler in compare to piston engine. Except application (like STOL/VTOL) of short hop-weight critical machines turboprop below 350HP is bad solution. I tend not to agree that we have "secret development" of small turboprop engines - physics is against us here. Much bigger chance for this class of power is reinventing piston engine in a form of Diesel cycle powerplant. Im still struggling to understand what may be gain from hybrid technology in A/C propulsion. Only answer are some distributed propulsion layout like this in multicopters or "blown wing". When we are watching on propulsion system efficiency only calculation doesn't looks encouraging at all.
 
Welcome to E-T, jaceb.

My comment... "I think that GA turbine technologies may be evolving fast, under the radar." was never intended to mean 'secret development'... simply work is on-going in engineering offices/labs
to understand/evolve turbine technologies. NOTHING remains static and evolution to revolution doesn't have to make headlines. In my life-time aviation evolution has been astonishing.

You mentioned PBS... which has been around awhile... YEP they won't evolve because certification/liability costs are massively burdensome... but their turbines have flown and found a small/strong niche market.

The issues that I have is with energy storage/density battery technology... which undeniably… is progressing rapidly 'under the radar' in labs all over the world. However EE-EL technologies rely on rare-earth minerals/metals technologies... and in a resource scarce world, this is troubling, to me.

Also, high density electrical power storage and distribution comes with it's own 'scary issues'... maintenance of electrical systems will be paramount due to inherent obvious hazards of arc-spark, bonding-grounding, etc.. and less obvious hazards due to degradation of components... including wiring and electronics... that will affect long-term system health. Lets not forget that in the 'real-world' we are talking about thousands of hours of operation under grueling circumstances... or far-worse... of intermittent service with long stand-down periods. And occasional mishaps/accidents.

Frankly I don't anticipate military applications for all-electric manned aircraft any time in the near future... except for battlefield stealth observation... where every 'radiated signature' is a 'tell'... so elimination/reduction of all signatures is a military necessity.

So my suggestion of an APU assisted/sustained small/compact electrical power-drive system is what I believe to be a viable compromise for NOW.

OH yeah... I do have a 'thing' for the elegant simplicity inherent in turbine power technology... but am NOT really wild-about turboprops. My experience is that turboprop engines are the mating of [2] propulsion systems that are equally complex/failure prone: [1] the turbine power plant... and [2] the mating gearbox/structure/propeller. For instance, my view of a C-130 aircraft is that it really has [8] 'dynamic engines'... 4-engines + 4-propellers/gearboxes.... whereas a C-17 has, simply, 4-turbofans.

NOTE.
My next door neighbor recently had a Generac standby generator installed... powered by home natural gas... I'm impressed with the technology/concept... that is already fairly old. In my next home I will have one installed... probably next generation... as-well-as electrical battery/energy storage from solar and possibly wind energy. I think micro/local electrical power generation is on the horizon... especially considering hazards/inefficiencies of long-distance electrical power transmission.

Just saying... in my rambling fashion...

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
 
oh, the expression "home natural gas" just fills me with, oh I don't know, grade 6 boy humour ?

another day in paradise, or is paradise one day closer ?
 
<tangent>
Our Generac 13kW standby running on propane has so far behaved as expected for almost a year.
I was surprised by the engineering, i.e. the engine is small, but is a 90 degree v-twin, so fairly well balanced, i.e., no ground-borne vibration.
</tangent>

Re fuel consumption:
Ten years ago, I compared the fuel consumption of a small Deere Diesel generator with a high-tech small turbine generator we were selling, both for terrestrial use.
The turbine's fuel consumption almost got down to equivalent Diesel levels, but only because it was equipped with a rotating ceramic recuperator to recover heat from the exhaust flow and use it to preheat combustion air.



Mike Halloran
Corinth, NY, USA
 
Will,
I tend to agree with most of your points. My background is aviation/electromechanics than i think i have pretty good insight on this problematics - and i'm still quite far from sharing world wide enthusiasm, circling around and shouting that we have long waited breakthrough. I think electric propulsion will not replace thermomechanical solutions any time soon.... but instead, this technology is creating new niche (pretty much like helicopters do have its own). In short words new technology, with great development capability but hanging on the promises from battery makers.... well, we will see....
 
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