blockage error-VSI

blockage error—VSI

An error in a VSI (vertical speed indicator) in which the static source is blocked. Since there is no differential pressure in the system when the aircraft climbs or descends, the VSI will continue to show a level flight even when the aircraft is climbing or descending. In the case of partial blockage, the VSI will underread, and there will be more than usual lag when the aircraft levels out.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved