First Electric Aircraft in Oz

[Derfred]

Petrol (gasoline) has around 50 times the watt/hour capacity of a lithium ion battery, by weight.

However, to be pedantic, this is not energy density.

Energy density is volumetric. With aircraft, we're more concerned with weight, which is termed specific energy.

Internal combustion engines at best convert 20% of their fuel energy to power. (I don't believe the 33% figure from a Piper quoted above, that defies physics.)

Whereas an electric drive can achieve over 90%.

This brings the specific energy "output" comparison down close to a factor of 10 rather than 50.

Lithium batteries are improving rapidly. Gasoline isn't, and neither are ICE's. So the gap can only narrow in time.

Also, other battery technologies are in the wings that could significantly improve upon Lithium in the coming decades.

[B772]

Derfred.

I agree. We are scratching the surface at present with battery technology. I was in China recently and looked at a 18V chainsaw (weighed 3.3 kg) that worked all day and charged overnight. No fuel spill = no risk of fire. Cost of chainsaw in China AUD47 or a decent bottle of red in Aust.

[StickWithTheTruth]

A petrol engine is 12-30% efficient, although similar figures are thrown out there regularly, however for a vehicle this must vary to an aircraft as much power is wasted on drivetrain and accessories. On the flip side, the prop has a loss etc. hard to calculate an exact figure.

[Ultralights]

Originally Posted by StickWithTheTruth

A petrol engine is 12-30% efficient,.

I would imagine an aircraft engine would be on the lower end of that scale, magneto ignition, most are carburettors, or rudimentary fuel injection, no quad valve engines, no constant mixture and timing adjustments via real time computer management systems... etc etc.

[peterc005]

Check out the "Brake specific fuel consumption" statistics; surprisingly, Lycoming engines can be comparable with modern car engines:

https://en.wikipedia.org/wiki/Brake_...el_consumption

[Slatye]

Originally Posted by Ultralights

I would imagine an aircraft engine would be on the lower end of that scale, magneto ignition, most are carburettors, or rudimentary fuel injection, no quad valve engines, no constant mixture and timing adjustments via real time computer management systems... etc etc.

On the other hand, they tend to operate in colder environments (at higher altitude) and use very high-grade fuel - both of which allow for efficiency improvements.

I agree that Piper's figures are probably not quite correct. I'm sure that the fuel consumption figure is right (because people use that for flight planning, and would notice if it was off by 30%+) but nobody really cares what percentage of rated power the engine is producing.

Probably the best person to solve this is mcoates - what is the fuel consumption of the petrol-powered Alpha, at the same weight and same cruise speed as the electric model? And what power is the electric motor using for that cruise?

StickWithTheTruth - prop loss should be the same for electric and avgas models, so it does not need to be considered.

Derfred - absolutely agree, eventually electric (of some form) is going to catch up to ICE. I think mcoates mentioned a fuel-cell aircraft that Pipistrel is working on, a neat stepping-stone between the two in that it uses "fuel" but drives an electric motor.

Give it 10 or 20 years, and I expect that a combination of better batteries and rising fuel prices will mean that electric planes are really giving avgas-powered ones a lot of competition - at least in the GA space. However, for now, avgas (or avtur for those that can use it) remains the only real option for reasonably long range.

[StickWithTheTruth]

My prop comment was when comparing the aircraft engine efficiency to that of a motor vehicle drivetrain.

[Sunfish]

Ultralights:

I would imagine an aircraft engine would be on the lower end of that scale, magneto ignition, most are carburettors, or rudimentary fuel injection, no quad valve engines, no constant mixture and timing adjustments via real time computer management systems... etc etc.

The Rotax 912 iS (electronic fuel injection) does all this ....to replicate exactly what can be achieved by running lean of peak in a conventional Lycoming or Continental fitted with an engine analyser and GAMI precision injectors.

Overhead cams/four valves/adjustable timing, etc. is not warranted on an engine spinning most of its life at 2500 rpm and 75% power. All that stuff does is increase parts count, complexity, weight and probability of failure.

I am currently deep into setting up a 912 iS and the wiring is quite complex. For example, you need seven switches to control the engine plus master switch if you follow the Rotax wiring recommendations. *

* ECU A & B, Pumps 1 & 2, Start Power tie, Start and emergency battery mode.

[mcoates]

This may also be of interest to you guys.

X-ALPHA

We are supporting the introduction of electric aircraft with the world's first commercially available virtual reality simulator. This simulator perfectly matches the aircraft performance and feel because it uses an actual full-size cabin simulator. The virtual reality goggles allow you to have a clear view in any direction including the ability to load topographic information for the area you are flying in.

This seems to be the way aviation is progressing. To be honest this is as close to real flying as I have ever seen, everything is identical including engine and cabin noise which has been recorded from actual flying conditions. It is worth having a look at to get an idea of the future of simulators
.

[Bend alot]

Check out the "Brake specific fuel consumption" statistics; surprisingly, Lycoming engines can be comparable with modern car engines:

wikipedia.org/wiki/Brake_specific_fuel_consumption


RPM is key - the more time you have, the more you can extract with older less advanced gear.

[Ultralights]

Originally Posted by Sunfish

Ultralights:



The Rotax 912 iS (electronic fuel injection) does all this ....to replicate exactly what can be achieved by running lean of peak in a conventional Lycoming or Continental fitted with an engine analyser and GAMI precision injectors.

Overhead cams/four valves/adjustable timing, etc. is not warranted on an engine spinning most of its life at 2500 rpm and 75% power. All that stuff does is increase parts count, complexity, weight and probability of failure.

I am currently deep into setting up a 912 iS and the wiring is quite complex. For example, you need seven switches to control the engine plus master switch if you follow the Rotax wiring recommendations. *

* ECU A & B, Pumps 1 & 2, Start Power tie, Start and emergency battery mode.

exactly, its the reason the rotax is so much more fuel efficient compared to similar power outputs of its continental counterparts. but most GA aircraft run large capacity slow turning old tech carby engines, so their specific efficiency would be on the lower end of the 12 to 30% efficient scale.

[Sam Rutherford]

Interesting thing about noise - for Pipistrel, their is exactly the same amount of noise for the petrol and electric versions. It's the prop that makes the noise...

[StickWithTheTruth]

Aviation needs someone like Dyson to come along and shake things up. If they can do vacuums, hairdryers, hand dryers and fans like no other, then maybe they can do something better than our primitive propellers.

[Goat Whisperer]

mcoates

the sim and the aircraft are fascinating. Thanks for taking the time to explain it all here. As soon as I can get a Perth trip I'll book a flight.

[Sam Rutherford]

Or Musk...

[Slatye]

Originally Posted by StickWithTheTruth

Aviation needs someone like Dyson to come along and shake things up. If they can do vacuums, hairdryers, hand dryers and fans like no other, then maybe they can do something better than our primitive propellers.

I'm not sure that there's much to be gained. Propellers already give about 80% efficiency (ie turning 80% of the power from the engine into thrust).

I can imagine improvements in the power system (eg. better batteries, fuel cells, etc) and airframe (lighter materials, less drag, etc) but I doubt that the propeller itself is going to disappear any time soon.

[Romeo Tango]

Electric aircraft must be the future for cost/reliability/environmental reasons but are probably not a sensible option today unless you want to be very green.

I did say this before, probably still valid.