Gas Hybrid Quad Rotor UAV?

While trying to think of a way to increase the payload capacity, size and flight time of a quad rotor aircraft I had an idea, which may or may not be novel and was wondering if anyone else has entertained it.

Could a combustion engine powered auxiliary power unit (APU) be installed on a quad rotor aircraft that is light and powerful enough to maintain a charge of the main battery that is used to power the motors and avionics?  In other words, could a small engine powering a generator keep up with the electrical demands of the aircraft that would have to carry it and the fuel?  

Here is a link to a company that produces generators for conventional RC aircraft:

Food for thought at least.

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  • What's the flight time of this??

    babak_ea said:

    Hello guy's

    Sergey said:

    Are there any videos from that device:

    Because I really doubt that it works in any way better (mean peaload or flight time) than a clean electric version of this.

  • Hello guy's

    Sergey said:

    Are there any videos from that device:

    Because I really doubt that it works in any way better (mean peaload or flight time) than a clean electric version of this.

  • Hi All,

    The company I work for, SkyFront, has created a gas-electric hybrid multirotor. For those who had any doubt, it is indeed possible to do this, even with the additional weight of the generator/motors and all. And using this setup, it can get over two hours of flight time. In the future it'll very likely get up to 4 hours with a decent sized payload.

    Here's a video of the maiden flight a few months ago: 

    We'll work on getting you all a longer video.



    • That is not a gas quad.

      This is a gas quad.


      • haha--is that yours? it's a beast.

        • Those look like Gluhareff pressure jets if I remember correctly which actually run on liquid propane.

          The reason the stainless steel they are made of is that dark is because they glow red to white hot when under power.

          Also the noise they produce is a deafening scream, they can be heard many miles away.

          Gluhareff Pressure Jet
          The Gluhareff Pressure Jet (or tip jet) is a type of jet engine that, like a valveless pulse jet, has no moving parts. It was invented by Eugene Mic…
    • Awesome job troy!

      The question wasn't whether it could be done or not. It had been done, and we have seen it.

      Instead the question is of practicality. Is it more efficient than one gad engine mechanically linked to 4 Variable Pitch props? Is it more robust? (Arguable... I would say no...). Last but not least, is there a benefit over a conventional gas heli?

      MultiRotors get to a point where they are no longer beneficial. This for example, is more complex (therefore more prone to failures) than a conventional heli, that can already carry the load for the intended flight time....
      • Hi Justin,

        1. I agree with you that the series hybrid drone is less efficient than a gas engine linked to 4 variable pitch props.
        2. But I do think it is more robust in the sense that with a series hybrid there are no belts/gears/axles and that in case of failure of the gas engine, power can easily be supplied by the battery.
        3. The benefits over a traditional helicopter are listed here:
          1. a series hybrid multirotor is actually much simpler. no reciprocating parts (other than the engine, which a heli would also have), gears or tail rotor to deal with. 
          2. redundancy/boost power with a battery, which leads to increased safety.
          3. this is related to complexity, but we built this series hybrid from scratch in a couple of months with no prior experience with multirotors or series hybrids. we would not have been able to do the same with a helicopter. and so, we expect the production version of this system to be much cheaper
          4. less vibration. because of electric, non-mechanical power transmission, you can soft couple the gas engine to the frame of the quadcopter. (i.e., you can isolate the vibrations with tuned rubber mounts.) 
          5. the ease of control of the multirotor is preserved.
          6. we can shroud the propellers for safety. not sure if you can do this with a heli, can you?

        I agree you take an efficiency penalty hit when you convert gas to electricity, but the ease of using electricity vs. dealing with a spinning mechanical shaft, in my opinion, more than makes up for it. if you wanted to hook a sensor payload up to it or add another motor/propeller combo, there would be little additional cost. 

        But that's just my two cents...I'm interested to hear more of your thoughts on this.



        • Troy,

          Are you building and selling them yet?  :)  I'm interested.


  • Someone may have already posted this, but the Director of National Intelligence's IARPA program is actively working on this.

    I spoke with the former program manager and they were making progress but they don't have a functional product despite soliciting major DOD vendors and big R&D budgets.

    That isn't to say it can't be done, just that it is pretty hard to do well. I would agree with Rob that the heli is the way to go for flight time. A gas heli gives you insane flight times without even trying very hard.

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