What feature of a vertical speed indicator is designed to correct indication lag?

The vertical speed indicator (VSI) is designed to provide pilots with information about the rate of climb or descent. One of the challenges with traditional VSI designs is indication lag, which is the delay in the instrument's response to changes in altitude.

The feature that addresses this issue is the internal lead, which incorporates a calibrated element that anticipates changes in altitude. Essentially, the internal lead accelerates the response of the VSI by adjusting the indication slightly in advance based on air pressure changes. This pre-response helps provide a more accurate and timely representation of the aircraft's vertical speed, reducing the lag that pilots might otherwise experience when making altitude changes.

In contrast, other options like external sensors, clock mechanisms, or pointer adjustments do not portray the same function of correcting the inherent response time of the instrument. External sensors typically relate to other measurement systems, clock mechanisms do not affect indication lag, and pointer adjustments focus on calibration rather than responsiveness.