What should a pilot do during a power off stall recovery?

During a power-off stall recovery, the appropriate action involves pitching the nose down to gain airspeed. This step is crucial because during a stall, the aircraft has lost lift due to insufficient speed; decreasing the angle of attack by pitching the nose down allows the wings to regain airflow and thus generate lift. By gaining airspeed, the pilot can recover the aircraft from the stalled condition more effectively.

In the context of the other options, increasing throttle immediately would not be appropriate during a power-off stall because the engine power is typically reduced during such a scenario, making it less relevant. Maintaining altitude until stabilized could lead to further increase in the stall condition, as the aircraft needs to be allowed to descend to regain speed safely. Performing a standard rate turn is not suitable during recovery from a stall, as it could exacerbate the loss of control and further complicate recovery efforts by increasing the load factor on the wings.

Therefore, pitching the nose down is the correct response to initiate recovery from a power-off stall.