119
edits
Changes
From CUGC Wiki
→Variometer (gliders)
=== Variometer (gliders) ===
You hopefully have realised from the discussions above that a variometer on a glider is not different from a vertical speed indicator on a powered aeroplane. Indeed, the instrument themselves are identical, the only difference is that a gliding variometer has its input connected to the total energy probe. In this way, the variometer tracks the change of the total energy of a glider rather than the change of altitude solely. "Stick thermals" are thus suppressed and a reliable indication of the natural lift in the atmosphere becomes available.
On a glider, normally two variometers are fitted. There is a mechanical one and an electronic one. The mechanical one does not require battery power to function, so it is operational even if the battery goes flat, which is a possibility in a very long decent soaring day. The disadvantages being:
#A mechanical variometer is usually quite sluggish in its response: it can take several seconds before the actual change of trend is accurately displayed, during which time there is a good chance that the glider has flown beyond the best bit of a thermal.
#You need to actually look at the variometer to get a reading. While this is not a huge problem in normal flight because most of the instruments you have to look at to read, due to the special interest of the variometer reading in a soaring flight, pilots can very easily get so distracted that their lookout significantly deteriorates.
It is not acceptable under any circumstance (with perhaps the exception of flying under IFR, which a glider does not normally do) to cease to look out properly and direct too much attention on the instruments, otherwise the flying safety is at stake. To help the glider pilots to read the variometer without directing the attention to the panel, electronic variometers can be introduced. These are more responsive and they sound an audible tone whose pitch depends on the variometer reading. Normally a continuous tone indicates the total energy is decreasing, while a discontinuous beep means the total energy is increasing.
[[Category:Theory]]
