To correct altitude discrepancies of less than 100 feet, which measure should be used?

To correct altitude discrepancies of less than 100 feet, the appropriate measure is to use half bar width on the altitude indicator. This approach is based on the fact that the standard altitude indication on the altimeter is marked by specific increments. When a discrepancy is noted, adjusting the aircraft's altitude by half the bar width allows for a precise and controlled correction, ensuring that small discrepancies are efficiently managed without overshooting the target altitude.

Using half bar width provides a balanced approach, allowing the pilot to make gentle adjustments and closely monitor the resulting changes in altitude. This level of precision is particularly important in maintaining altitude during instrument flight, where minor deviations can have a significant impact on safety and navigation. It helps maintain a smooth control of the aircraft and reduces the chances of altitude overshoot or oscillation around the desired altitude.

In contrast, options that suggest using full bar width or other fractions would not provide the same level of accuracy needed for small corrections, which is why they are less suitable for addressing discrepancies of this magnitude.