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indication toward north; deceleration causes an indication toward south. 

## Oscillation Error 

Oscillation is a combination of all of the errors previously mentioned and results in fluctuation of the compass card in relation to the actual heading direction of the aircraft. When setting the gyroscopic heading indicator to agree with the magnetic compass, use the average indication between the swings. 

## The Vertical Card Magnetic Compass 

The vertical card magnetic compass eliminates some of the errors and confusion encountered with the magnetic compass. The dial of this compass is graduated with letters representing the cardinal directions, numbers every 30°, and tick marks every 5°. The dial is rotated by a set of gears from the shaft- mounted magnet, and the nose of the symbolic aircraft on the instrument glass represents the lubber line for reading the heading of the aircraft from the dial. [Figure 8-38] 

## Lags or Leads 

When starting a turn from a northerly heading, the compass lags behind the turn. When starting a turn from a southerly heading, the compass leads the turn. 

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## Eddy Current Damping 

In the case of a vertical card magnetic compass, flux from the oscillating permanent magnet produces eddy currents in a damping disk or cup. The magnetic flux produced by the eddy currents opposes the flux from the permanent magnet and decreases the oscillations. 

