User manual

Discus Glider X
Aerosoft GmbH 2009
42
or ridge flying a needle pointing upwards is generally a good thing,
while the needle rapidly rotating anti-clockwise around the dial
heading towards the negative lower half is a sign that you should
speed up and get out of the sinking air you are in.
Total Energy Compensated variometer
The mechanical ‚Winter‘ variometer in the Aerosoft
Discus below and to the right of the SDI C4 has been
configured to continuously display your ‚Total Energy
Compensated Climb Rate‘. This is the traditional
value that has been relied upon by glider pilots for
over fifty years, giving the climb rate of the glider
after removing the effects of the pilot pulling or
pushing on the joystick. Pulling back on the stick causes the glider to
climb, but also to decelerate, and by reading both the static air
pressure (altitude) and the pitot pressure (airspeed), the effect of the
joystick movement can be compensated for, hence „Total Energy Com-
pensation“. If your airspeed is not changing, the Total Energy climb
rate will equal your true climb rate.
This reading is far more useful than the simpler true climb rate, as the
information that glider pilots really need to stay in air is the change in
energy stored in the aircraft, either in kinetic (altitude) or in potential
energy (speed). If he is low and fast he can exchange speed for
altitude, if he is high and slow he can exchange altitude for speed.
Excluding the loss of energy due to drag for simplicity, the total energy
stays the same. What the glider pilot needs to know is if he losing or
gaining Total Energy. If he is in a thermal and gaining altitude without
pitching up he gains energy (in the form of altitude), if he is in
descending air he is losing energy.
The Total Energy Compensated variometer provides that information
„It shows the vertical speed while effects of aircraft maneuvers are
eliminated. For a mechanical vane vario this is achieved by using
special static pick-up nozzles which combine static pressure and pitot
pressure“.