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I have edited this to one question and thank you for all the feedback .

I am trying to understand if there are any theoretical improvements in range when applying electric propulsion to large commercial craft such as the A380, or if the theory favours smaller commercial turbine powered craft.

A good answer for a Cessna seems to be the specific capacity of the battery = range in nautical miles. However the weight of the fuel in a Cessna is under 10% of its MTOW, whereas an A380 tops 40%. The second good answer asserts that you would design a new aircraft, you don't convert an existing one that has been optimised for chemical combustion at the point of propulsion. The proof here is provided by the Sun Flyer. The third theory is that doesn't matter how big or small the craft is, it's a ratio of battery weight to MTOW.

Whether we decide to convert an aircraft or design a new one, suppose we had to make an all electric commercial aircraft with the greatest possible range, would you start big, such as with an A380 or start with the smallest aircraft and why?

Some A380 facts to use are here: https://web.archive.org/web/20161012152549/http://www.airbus.com/fileadmin/media_gallery/files/tech_data/jetFamily/media_object_file_A380_specifications.pdf Maximum landing weight= 386 tonnes Empty weight=282 tonnes Typical payload=66 tonnes

Thanks for the careful thought on the replies already.

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Let's suppose we had to convert a commercial aircraft to an all electric craft tomorrow and use all the available parts, batteries, thrust devices and airframes becoming available, as well as take off and land on conventional runways, with a typical payload etc, would this thing fly?

This amount of specificity makes what would normally be pretty silly into something that can, if only just, work for a question.

The best aviation-specific electric engines are only somewhat heavier per unit weight (but much less powerful in absolute terms) than the best turbine engines, and will make up for it in using bus bars and distribution boards instead of extensive fuel piping, heating and pumps.

You could not simply stack a lot of small electric engines under the wings, as that would ruin the aerodynamics - the wing couldn't produce any lift due to fast jet air flowing under it. It would either have to be an all-custom design, or the engines would have to replace the turbines directly. Such engines are not currently available, but, with superconducting rotors and stators, are potentially achievable within the next decade.

Per calculations done here based on the Breguet equation, a perfect electric airliner will fly up to 10 nmi for each 1% of its weight that is dedicated to the battery. More precisely it's 9.9 nmi at a 0-100% discharge cycle with 100% efficient fans. A more realistic but still optimistic number is 7 nmi, with less than perfect fans and allowing for a 20%-95% cycle that accounts for degradation and emergency reserves.

At takeoff, the A380 can carry up to 254 metric tons of fuel, but that would only leave 44 tons for the payload, supporting up to 400 passengers, and its maximum landing weight would require less than 100 tons of fuel aboard.

Assuming the hypothetical electric 380 is reinforced for a MLW equal to MTOW (575 tons), and counting on savings from general modernization and removing the fuel system to absorb that reinforcement weight, a more realistic battery weight is 230 tons, allowing for a 68-ton payload, supporting the usual 600-passenger capacity. This makes for a 40% battery weight, and thus approximately 280 nmi or 520 km operational range.

So the short answer is: if electric engines with similar power and size to the Trent 900's cores can be produced, the airplane will fly, but its operational range would be just ~500 km, less than 4% of what the current A380 is capable of.

Practically, you would not use an A380 to fly short distances, due to its complexity in ground handling of the two flight decks. There was the Boeing 747SR, built just for the Japanese domestic market, to save on airport slots. The largest plane you'd use has to be something versatile and quick to load and unload, such as the A350 XWB.

But there are short routes for small aircraft 1that are simply begging to be electrified, and if the legacy factor and lack of infrastructure don't interfere, they likely will.

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  • $\begingroup$ you're missing to factor in that those best electric engines produce a fraction of the power of the engines installed on an A380, so you'd need many more of them. Which makes the equation even less appealing, as it'd likely run out of electricity before even reaching the runway. $\endgroup$
    – jwenting
    Jun 12, 2019 at 9:31
  • $\begingroup$ @jwenting This is under the assumption that all-superconducting engines that can replace the Trent 900's cores within a similar space envelope can be manufactured. It's difficult, but I'd rate it as short of impossible. $\endgroup$
    – Therac
    Jun 12, 2019 at 9:40
  • $\begingroup$ That'd depend heavily on the development of cheap high temperature superconductors, something we're far short of. Theoretically possible, but fantastically expensive. $\endgroup$
    – jwenting
    Jun 12, 2019 at 9:42
  • $\begingroup$ @jwenting "Cheap" was never part of the equation. I'm aware of the development of helium+nitrogen cooled SC-rotor, SC-stator engines based entirely on current HTSC technology. Difficult, but it might be possible. And the gap to cover isn't that wide. The Emrax is a simple glycol-cooled copper-wound motor - it's just scalability that HTSC need to address. $\endgroup$
    – Therac
    Jun 12, 2019 at 9:47
  • $\begingroup$ Considering photovoltaic effect it is totally insufficient due to the ratio of skin area to Weight Using the wings to be filled with batteries cells is non sens for maintenance. Continued on next comment $\endgroup$
    – user40476
    Jun 12, 2019 at 15:45

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