atmospheric pressure as though the aircraft were
standing still in the air. The static line applies this
outside air to the airspeed indicators, the
altimeter, and the vertical speed indicator.
Airspeed Indicators
Readings from an airspeed indicator are
useful. They are used to estimate ground speed
and to determine throttle settings for the most
efficient flying speed. These readings also provide
a basis for calculating the best climbing and
gliding angles. They warn the pilot if diving speed
approaches the safety limits of the aircraft's
structure. Since airspeed increases in a dive and
decreases in a climb, the indicator is an excellent
check for maintaining level flight. Figure 6-4
Figure 6-3.-Pitot-static system.
indicator calibration allows various air pressures
to cause different readings on the dial. The
purpose of the airspeed indicator is to interpret
pitot air pressure in terms of airspeed in knots.
Generally, static air vents (fig. 6-3) are small
calibrated holes in an assembly mounted flush
with the aircraft fuselage. Their position is in a
place with the least amount of local airflow
moving across the vents when the aircraft is flying.
Static means stationary or not changing. The
static part of the pitot-static system also introduces
Figure 6-4.-(A) Airspeed indicator; (B) maximum allowable
outside air. However, it is at its normal outside
airspeed indicator.
