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I'm having a hard time understanding the correlation between the wind gusts (where are they coming from, what are they affecting) and why, in a nose left situation, the stabilator is driven down.

I keep thinking it would make sense for it to go up (e.g. left pedal, more tail rotor torque, tail up, nose down.

sideslip to pitch coupling to reduce susceptibility to gusts. When the helicopter is out of trim in a slip or skid, pitch excursions > are also induced as a result of the canted tail rotor and downwash on the stabilator.

Lateral accelerometers sense this out of trim condition and signal the stabilator amplifiers to compensate for the pitch attitude change (called lateral to sideslip to pitch coupling).

Nose left (right slip) results in the trailing edge programming down. Nose right produces the opposite stabilator reaction.

If the stabilator drives down, this will make the nose go down further.

I know I'm missing something big here but can't put it together.

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    $\begingroup$ Nothing is clear about this question. I have absolutely no idea what you're asking! $\endgroup$
    – Jamiec ♦
    Oct 13, 2016 at 16:29
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    $\begingroup$ This feels like it could be a good question if it is properly edited. Do you have any time to stop by our chat room and maybe explain the question in detail? We may be able to help you rephrase it so you can get a better answer. chat.stackexchange.com/rooms/12036/the-hangar $\endgroup$
    – Jay Carr
    Oct 13, 2016 at 17:35
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    $\begingroup$ @Jamiec Is it then a requirement that everyone should understand all questions or they should be closed? I understand it, and have edited in an attempt to make it clearer for more people but in my view, this is a good question. $\endgroup$
    – Simon
    Oct 13, 2016 at 17:40
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    $\begingroup$ @KorvinStarmast Ah, that makes sense now. I've approved the edit but I don't quite have enough rep for it to stick without another vote. This question also needs to be re-opened, it's ridiculous that it was closed in the first place. $\endgroup$
    – Simon
    Oct 13, 2016 at 18:41
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    $\begingroup$ @Jamiec Perhaps one for meta? "I think we can safely say that a reasonable person, who is reasonably knowledgable with a certain amount of Aviation knowledge should understand all questions, yes" - I meet the criteria, but I do not understand all fixed wing questions, nor do I vote to close them because of this. $\endgroup$
    – Simon
    Oct 13, 2016 at 20:03

1 Answer 1

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The sideslip to pitch coupling is a result of the canted tail rotor and the asymmetry of the main rotor downwash. The tail rotor thrust pushes the tail to the right and upward (pitch down). The main rotor downwash across the tail boom also generates a pitch up motion. The 'static' position of the stabilator is set (stab range is 10 deg up to 45 deg down based on airspeed) to counter this pitch tendency.

A right sideslip condition will result in a reduction of tail rotor vertical thrust resulting in a pitch up motion. The stabilator is programmed downward to counter the pitch up. Conversely a left sideslip will result in increased tail rotor vertical thrust and a pitch down motion. In this case the stabilator will be programmed up to counter the downward pitch.

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