PRINCIPLE AND OPERATION VARIOMETER
INTRODUCTION:
we are going to see another flight control instrument it gives the vertical speed
The VSI is a vertical speed indicator.
It allows to fly the plane to climb speed or especially for blind approaches to a fixed rate of descent.
It is also used for flights landing.
2. OPERATING PRINCIPLE:
2.1. SCHEMATIC DIAGRAM:
If the static pressure decreases, the capsule pressure will tend to decrease while the orifice lets through a thin net insufficient air to instantly restore balance.
Then there is deformation of the capsule which is maintained during the whole time of the pressure variation, therefore the variation in altitude. 
2.1.1. HORIZONTAL OR FLIGHT LEVEL
P = P, the capsule remains at rest, the indication is zero.
2.1.2. FLIGHT UP (CABRE):
P <P because P decreases instantly and P, with a slight delay due to the orifice in the capsule contract indicating an upshift.
2.1.3. VOL DOWNHILL:
P> P because P increases instantly and P, with a slight delay due to the orifice: the capsule expands indicating a descent rate.
خارج الموضوع تحويل الاكوادإخفاء الابتساماتإخفاء