Swashplate leveler

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A mechanical swashplate leveler showing a slightly out of level swashplate.
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A swashplate leveler is a device for ensuring that the swashplate is perpendicular to the main mast. By ensuring that the swashplate is 'flat' it reduces the need for trim (assuming perfect weight balance), and makes setting up the head much easier.

In general, the head (except for the swashplate) must be removed to use the leveller.

Swashplate levelers take two forms:

  • Bubble level
Two bubble levels at right angles are attached to a disk with a hole or slot cut in it, allowing it to rest on the swashplate. Assuming the mast is exactly vertical, any deviation of the swashplate from horizontal will be show by the bubble levels. Bubble level levellers do not have to be made precisely for each different size helicopter.
  • Mechanical level
A disk or cone slides closely over the main mast, and rests on the high points of the swashplate (usually where the servos attach). Any deviation from level will be seen as gaps between the leveller and the swashplate.

A mechanical swashplate leveler can be improvised by wrapping a piece of solder to the top of the mast (or a hex key attached to the mast with cable ties or rubber bands), and aligning it to touch one of the linkage points on the swashplate. The mast can then be rotated to compare and adjust the other points. Alternatively, changes in the pitch angle of a paddle as the helicopter is rotated will indicate an out of level swashplate.

In use, the transmitter is set for a zero degrees collective pitch position (with no trim!). First the pushrod lengths are adjusted to bring the swashplate close to horizontal (perpendicular), and then subtrim can be used to fine tune the swashplate to level. The collective can then be raised to full positive and negative, and CCPM interactions reduced by adjusting the servo throws.

There is a final sort of leveler that fits between the body of the helicopter and the bottom of the swashplate. This allows the swashplate zero-degree collective pitch position to be set and levelled in one operation, but doesn't help remove CCPM interactions. It also risks overheating and destroying cyclic servos if one or more servos are pulled too low and bind against the leveller.

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