variometer

A variometer is an instrument used in aviation and soaring sports to measure the rate of altitude change, i.e., the vertical speed of the vehicle. It indicates whether the aircraft is climbing or sinking and how quickly, and many models also provide altitude or altitude gain over a period. Variometers are common in gliders, sailplanes, paragliders, and hang gliders, where understanding vertical airflow is essential for efficient flight and cross-country navigation. They may be used with audio outputs to provide continuous feedback without requiring continuous visual attention.

Principle and types

Traditional variometers relied on mechanical, pressure-based systems. An aneroid capsule expands or contracts with ambient air pressure; the mechanical linkage translates this into a deflection representing vertical speed, sometimes with a clockwork or pneumatic integrator to show altitude changes. Modern variometers are electronic and typically use a barometric pressure sensor to estimate altitude and its rate of change, processed by a microcontroller to display vertical speed. Some systems fuse GPS-derived altitude data with barometric measurements to improve accuracy and reduce drift in varying weather conditions. Variometers may be purely visual, purely audio, or offer both, with audio variants producing tones or bursts that rise with lift.

Uses and considerations

Pilots use variometers to locate thermals and rising air, optimize glide performance, and maintain situational awareness during flight. They are valued for real-time feedback and the ability to gauge thermal strength and persistence. Limitations include sensitivity to pressure changes, temperature, and GPS signal availability in electronic variants. Proper calibration and understanding of the specific instrument are important for accurate readings.

See also: vertical speed indicator, altimeter, glide computer.