So, I was skiing sometime ago, and unfortunately, another skier got injured. So, a heli was flown up to get the injured skier. The rotor blades were stationary, but I still heard some sort of engine like sound. Does anyone know any helicopters capable of doing this sort of thing?


Yes, many helicopters (but not all) can do this. There are 2 main methods:

  • a clutch between engine and rotor system
  • for turbines only: a rotor brake on the engine output shaft. The engine contains a free turbine (i.e. a turbine stage that isn't attached to the compressor) that drives the rotor system. If you brake this shaft, the engine can run without spinning the rotors.
  • $\begingroup$ I can't seem to find any of these of the Bell 412 or AS350 for example. Any documentation? $\endgroup$ – lpydawa Dec 19 '19 at 10:47
  • $\begingroup$ Bell 412 engines: euravia.aero/engine-detail/pt6t-3df $\endgroup$ – Hobbes Dec 19 '19 at 11:00
  • $\begingroup$ Also, is there a term for this method of stopping blades while engine is running? $\endgroup$ – lpydawa Dec 19 '19 at 11:34
  • $\begingroup$ so technically I can run the engines at idle, and apply rotor brake? And does that mean that the 412 has no clutches? $\endgroup$ – lpydawa Dec 19 '19 at 11:35
  • 1
    $\begingroup$ The brake is called a rotor brake. The procedure would depend on the helicopter, but generally, yes I'd expect you can idle the engine and apply the rotor brake. Some rotor brakes are automatic, I see. $\endgroup$ – Hobbes Dec 19 '19 at 11:42

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