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pilot values in front and dual pilot values for the second seat instrument. Marked for specific aircraft, some may have empty ballast and full ballast values. 

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Variometers are sensitive to changes in pressure altitude caused by airspeed. In still air, when the glider dives, the variometer indicates a descent. When the glider pulls out of the dive and begins a rapid climb, the variometer indicates an ascent. This indication is sometimes called a stick thermal. A glider lacking a compensated variometer must be flown at a constant airspeed to receive an accurate variometer indication. 

## Total Energy System 

A variometer with a total energy system senses changes in airspeed and tends to cancel out the resulting climb and dive indications (stick thermals). This is desirable because the glider pilot wants to know how rapidly the air mass is rising or descending despite changes in airspeed. 

A popular type of total energy system consists of a small venturi mounted in the air stream and connected to the static outlet of the variometer or simply as a slot or pair of holes on the back side of a quarter inch vertical tube. When airspeed increases, more suction from the venturi moderates (offsets) the pressure at the static outlet of the variometer. Similarly, when airspeed decreases, reduced suction from the venturi moderates (offsets) the pressure at the static outlet of the variometer. If the venturi is properly designed and installed, the net effect is to reduce climb and dive indications caused by airspeed changes. To maximize the precision of this compensation effect, the total energy probe needs to be in undisturbed airflow ahead of the aircraft nose or tail fin (the "Braunschweig tube", the long cantilevered tube with a kink in the end that can be seen projecting from the leading edge of the tail fin on most modern sailplanes.) [Figure 4-27] 

Another type of total energy system is designed with a diaphragm-type compensator placed in line from the pitot tube to the line coming from the reference chamber (thermos or capacity flask). Deflection of the diaphragm is proportional to the effect the airspeed change has on pitot pressure. In effect, the diaphragm modulates pressure changes in the capacity flask. When properly adjusted, the diaphragm compensator does an adequate job of masking stick thermals. [Figure 4-28] 

## Netto 

A variometer that indicates the vertical movement of the air mass, regardless of the glider’s climb or descent rate, is called a Netto variometer system. Some Netto variometer systems employ a calibrated capillary tube that functions as a tiny 

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