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What will be the effect on the VSI if, during a steady climb, an aircraft experiences a blockage in the static pressure system?
  • A
    The rate of climb indicated on the VSI freezes at the indication when the blockage occurred.
  • B
    The rate of climb indicated on the VSI decreases.
  • C
    The rate of climb indicated on the VSI increases.
  • D
    The VSI indication slowly moves to zero.

A barometric type Vertical Speed Indicator (VSI) uses the rate of pressure change to give the rate of climb or descent indications. Vertical speed indicators are supplied with static pressure from the static ports.

The VSI is supplied with static pressure only, and thus is only affected by blockage of the static port of leakage of the static pressure line.

  • A blockage of the static port makes it impossible for pressure changes to enter the static line and traps the pressure that existed at the moment when the blockage occurred. Since no pressure changes are transmitted to the capsule, the generation of a differential pressure over the capillary is impossible, and the conventional VSI indicates zero independently from the vertical rate.

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