variometri

A variometer is an instrument used in aviation to indicate the rate of climb or descent of an aircraft. Also known as a vertical speed indicator (VSI), it measures the change in static air pressure over time. As an aircraft ascends, the surrounding static air pressure decreases, and as it descends, the pressure increases. The variometer detects these subtle changes and translates them into a visual indication, typically on a dial or a digital display.

The instrument works by comparing the ambient static air pressure with a reference pressure that is allowed to change only very slowly. This is usually achieved through a small, calibrated leak into a reservoir within the instrument. When the aircraft's altitude changes, the ambient static pressure shifts immediately, while the pressure in the reservoir lags behind. The difference between these two pressures causes a diaphragm within the variometer to deflect, moving a needle on a gauge. A climb is indicated by a positive reading, while a descent is shown by a negative reading. Most variometers are calibrated to display vertical speed in feet per minute or meters per second.

Variometers are essential for pilots to maintain a desired altitude, execute precise climbs and descents, and to detect stalls or other aerodynamic anomalies. They provide crucial information for navigation, fuel efficiency, and passenger comfort. While modern aircraft often integrate this function into more complex glass cockpit displays, the fundamental principle of measuring pressure change to indicate vertical speed remains the core of the variometer's operation.