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I was wondering, if a pilot uses full input on cyclic and collective, what pitch angle can be achieved for the rotor blades? Is there a mechanical stop to prevent extreme angles of attack? And how would that interact with the blade pitch needed for auto-rotation?

Thanks!

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Maximum pitch angle would totally depend on the type of helicopter you are flying. Each helicopter has its own set of limitations and pitch angles depending on the blade, rpm, etc. The controls include a mechanical stop, and you would hit that limit sooner or later if you put in an overly aggressive control input on the cyclic, or full collective up or down. Think of it as the same way you would hit the outside edge of the control on a video game joystick.

In "real life", the pitch angle numbers are irrelevant to a helicopter pilot. During autorotation, the RPM of the spinning blades is maintained by reducing the pitch angle allowing an upflow of air from the descent to maintain the rotors spinning - similar to blowing air on a fan in order to keep the fan blades moving. The rotor RPM can be adjusted through up and down collective movements, which will in turn increase or reduce the RPM required.

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  • $\begingroup$ Thank you for the answer! What I meant was specifically the deflection of the pitch angle from its neutral position. How many degrees about the feathering axis of the blade can the pitch links induce. It's more about the mechanics of the rotor hub/controls, not the piloting experience side of things. I don't think it would matter whether the engine is on or off for that, or the current RPM. $\endgroup$ – IratePirate Mar 23 at 17:55
  • $\begingroup$ On the Robinson R44 for example (Robinson publishes their maintenance manual so you can reference section 10.122, Page 10.11), full collective down pitch 1-2 degrees down, 11.5-12.5 degrees up. $\endgroup$ – Dan Prat Mar 24 at 15:49
  • $\begingroup$ Perfect! Thank you! $\endgroup$ – IratePirate Mar 25 at 15:38
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Each control (collective, longitudinal cyclic, and lateral cyclic) can provide a specific range of blade root pitch. E.g. the collective may pitch the blade a total of 20 degrees from minimum to maximum position.

The angle of attack (AOA) depends on the flight condition. The same "control blade angle" will result in a different AOA in descent compared to climb. There is no mechanism to explicitly limit this AOA.

Notice above I said the pitch angle range only! The physical pitch angles depend on helicopter-specific mechanical settings. E.g. if a helicopter will be flown in a region of very high air density the maintainer will adjust that 20 degree collective range to be at smaller blade angles (say -3deg to +17deg instead of 0deg to +20deg). See this link for more details.

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