A static line blockage means that the static pressure in the VSI instrument capsule and case via the metering unit both remain a constant value. Therefore, the VSI display will read zero at all times regardless of any actual change in the aircraft's rate of climb of descent (ROC/ROD). The actions for a blocked static line causing an unreliable VSI reading would be

1. To ensure that the pitot static probe anti-icing heating (pitot heat) is on, if applicable.

2. To use an alternative, such as a static source or an air data computer, if applicable.

3. To use a limited flight panel, i.e., altimeter, if available.

4. To fly correct attitude and power settings.

For climbs and descents, calculate rate of climb or descent (ROC/ROD) either from the altimeter or from approximates given known aircraft attitude and power performance.