The vario used in gliders is different in many respects than the simple VSI fitted in most light aircraft. The most common glider varios are compensated by also having a pitot source in addition to a static feed. This goes someway to eliminating sudden and short term changes to the indication which may also be caused by the pilot making pitch changes. A vario with an associated capacity flask is another method amongst others used. The gliding vario is also calibrated in knots rather than feet per minute.
The glider pilot seeks a constant upward rise in an air mass and similarly needs to be aware of a downward trend. Short term fluctuations are of little value to the glider pilot, but this is also true for powered pilots although for a different need. Because of it's limitations a simple VSI should be observed over a period of time to interpolate a trend. In light aircraft the altimeter is good enough to do this and fits within a normal instrument scan technique.
Power + attitude = performance in the first instance, not power + altimeter. Having set the power and attitude for S+L it is the stable airspeed that confirms you have done this correctly. Only when the speed has stabilised should the altimeter be assessed. Particularly important in the climb of course.
Last edited by Fl1ingfrog; 14th Feb 2018 at 12:57.