To establish proper airspeed in straight-and-level flight, which instrument is primary?

The primary instrument for establishing proper airspeed in straight-and-level flight is the airspeed indicator. This instrument displays the speed of the aircraft relative to the surrounding air, which is essential for ensuring safe and efficient flight operations. Maintaining the correct airspeed is crucial for various phases of flight, including takeoff, cruise, and descent. It helps pilots avoid stalling by ensuring the aircraft is flying above the minimum speed required for controlled flight.

In straight-and-level flight, the airspeed indicator provides immediate and direct feedback to the pilot regarding their current speed. By monitoring this instrument, pilots can make necessary adjustments to the throttle or pitch attitude to maintain their desired airspeed and ensure optimal performance of the aircraft.

The manifold pressure gauge, attitude indicator, and vertical speed indicator, while important for various aspects of flying, do not directly measure the aircraft's airspeed. The manifold pressure gauge is used primarily in piston-engine aircraft to assess the pressure within the intake manifold, while the attitude indicator helps pilots maintain the aircraft's orientation relative to the horizon. The vertical speed indicator shows the rate of climb or descent, but none of these instruments provide the direct airspeed information needed for maintaining proper flight parameters in straight-and-level flight.