Which instrument helps a glider pilot determine vertical speed?

The variometer is the instrument specifically designed to help a glider pilot determine vertical speed. It measures the rate of climb or descent of the glider, typically expressed in feet per minute or meters per second. By detecting changes in air pressure as the aircraft ascends or descends, the variometer provides pilots with crucial information on their vertical movement, allowing them to optimize their flight path, find lift, and manage their glide performance effectively.

Unlike the altimeter, which indicates altitude rather than the rate of climb or descent, or the airspeed indicator, which measures horizontal speed, the variometer focuses solely on vertical performance. The magnetometer, while useful for navigation by indicating heading based on the Earth's magnetic field, does not provide any information relevant to vertical speed. Thus, the variometer is the essential instrument for glider pilots to gauge their vertical speed accurately.