What initial cockpit indications may a pilot observe when encountering a change from headwind to calm wind?

When transitioning from a headwind to calm wind, the pilot will notice a decrease in indicated airspeed. This phenomenon occurs because headwind contributes to the aircraft's effective airspeed through the atmosphere, essentially "adding" to the speed as perceived relative to the ground. When the headwind is removed, the aircraft loses this additional relative speed, causing the indicated airspeed to decrease.

As the indicated airspeed declines, the aircraft's behavior in pitch and altitude also changes. Typically, the aircraft will pitch down slightly due to the reduced lift generated at lower airspeed. In terms of altitude, the decrease in airspeed can lead to a descent unless corrective actions, such as adjustments to the throttle or pitch attitude, are taken by the pilot.

The combination of these factors leads to a scenario where indicated airspeed decreases, the aircraft pitches down, and the altitude also decreases, accurately reflecting the aircraft's response to the change in wind conditions.