Pitch gauge

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Align pitch gauge
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A pitch gauge in use, showing 10 degrees of collective pitch.

A tool used to measure the pitch angle of the main rotor blades. The pitch gauge is slipped onto a blade, and the top or the bottom of the gauge is aligned visually with the flybar.

There are two ways that the pitch gauge can be used:

  • The transmitter is set to the desired collective stick position, and the pitch gauge pointer is moved until the top or bottom of the gauge is aligned to the flybar. The current blade pitch angle can then be read off the pitch gauge.
  • The desired pitch angle for a stick position can be set on the gauge, and the locking screw tightened. Set the collective stick position, and then change the relevant value on the radio (for example, the collective pitch servo throw, CCPM collective pitch parameter or pitch curve point) until the flybar and pitch gauge come into alignment. The desired pitch angle is now set for that stick position.

While most commonly used to set collective pitch range, it can also be used to set cyclic pitch range, by holding the cyclic control over to one side while making the measurements from zero degrees collective pitch.

Pitch gauges come in a number of sizes, suitable for different blade chords (widths).

There are a number of points to ensure accurate use of a pitch gauge:

  • The flybar should be held parallel to the tail boom, and so at right angles to the main mast (it's not quite in the picture, but this amount of error is acceptable).
  • The blades must be pulled straight out from the blade grips.
  • The pitch gauge must be straight on the blade.
  • Finally, it is important to look straight down the blade, so that the blade, blade grips and the main rotor hub form one line.
  • It can be very awkward to align the top or bottom of the gauge with the flybar (the example here is taken looking significantly up at the rotor disk from underneath); it can be useful to carefully add another horizontal reference line to the pitch gauge.

See also

External links

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