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I've been reading about NASA's experimental GL-10 Greased Lightning tilt-wing aircraft with interest.

My understanding is that this is a diesel-electric hybrid aircraft uses stored electrical energy to satisfy the much greater need for thrust during takeoff (and landing?), but for regular flying runs off fewer propellers powered by the 2x 8hp diesel engines (which presumably also are recharging the Li-Ion batteries for the next takeoff/landing) to achieve better efficiency.

The answers to this question show that diesel engines are generally poorly suited to aero applications, generally due to weight and complexity.

Why then does the GL-10 use diesel fuel instead of more common aero fuels?

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    $\begingroup$ Diesel is much more available world-wide than 100LL, which is currently in research to be phased out at some point in the (distant) future. 100LL is usually only available at airports, Greased Lightning is designed to operate outside of the airport environment. It would be a disadvantage to have to take a tank of 100LL or avgas for this rather than fill up at the local fuel depot. $\endgroup$
    – Ron Beyer
    Jan 3, 2017 at 21:31
  • $\begingroup$ Now that we have better materials to make diesels reasonably light, they are well suited to aero applications and the answers you link to do say that. $\endgroup$
    – Jan Hudec
    Jan 3, 2017 at 23:05
  • $\begingroup$ I know I wrote that modern, turbocharged Aerodiesels are complex, but they can be very simple if you do away with charging and electronic control. If you have ever tried to shut off a model diesel engine you know that these things are super reliable, robust and efficient. $\endgroup$
    – Peter Kämpf
    Jan 3, 2017 at 23:30

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There is a bit of a misnomer here, although the plane runs diesel engines it most likely does not run traditional diesel fuel as you would find at a gas station. Diesel engines can be run on Jet-A which is available far more widely than 100LL at airports outside the US which Ron mentions.

There are even some applications for diesel engines in GA as noted in your linked question the diamond twin star and now the Piper Archer DX have successfully been running diesel engines for some time now.

According to this paper the Cosworth AG engine was considered which the Navy has already been bench testing with JP-5 and JP-8 jet fuel. Presumably the GS motor they chose runs similarly.

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    $\begingroup$ The misnomer in question is calling the fuel “diesel” — a Diesel (compression-ignition) engine will happily run on about anything as long as it burns and has enough lubricating properties. $\endgroup$
    – Jan Hudec
    Jan 3, 2017 at 23:05

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