What are the drawbacks of this compared to coaxial configuration with a turboshaft engine?

  • $\begingroup$ Even on piston engine helicopters the rotors are not directly connected to the engine, they go through a transmission. I don't see why you couldn't, although the O-320 probably wouldn't have enough power to turn two full-size rotors. $\endgroup$
    – Ron Beyer
    Jan 28, 2021 at 17:56
  • $\begingroup$ It is theoretically possible to mount coaxial helicopter rotors on any engine, but it would not be economically feasible on a small engine like an O-320. Turboshaft engines typically have much more power than an O-320. Why would you compare an O-320 engine to a turboshaft engine? $\endgroup$ Jan 28, 2021 at 17:57
  • $\begingroup$ What the hell... Once again a totally legit question here, and someone gives it a minus one. Come on guys/gals... at least have the courtesy of commenting why you think this is a bad question! $\endgroup$
    – Jpe61
    Jan 28, 2021 at 19:06

1 Answer 1


Stan Hiller's earliest helo designs were coaxial and used relatively small 4-cylinder aircraft engines to drive the coax transmission, so it is indeed possible to power a small coaxial helicopter with a relatively small piston engine.

Hiller also found that autorotating a coax main rotor blade setup was difficult and so his later designs used a more conventional single main rotor blade and a tail rotor.

  • $\begingroup$ That's interesting about the autorotation problems. Must've been related to the mechanism he was using to get differential torque for yaw control? $\endgroup$
    – John K
    Jan 29, 2021 at 1:32
  • $\begingroup$ do not know... -NN $\endgroup$ Jan 29, 2021 at 2:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.