What is the primary function of the attitude indicator in a helicopter?

The primary function of the attitude indicator in a helicopter is to indicate pitch and roll attitude. This instrument is crucial for pilots as it provides real-time information about the aircraft's orientation relative to the horizon. The attitude indicator helps pilots maintain control of the aircraft by showing how the helicopter is positioned in three-dimensional space, specifically in terms of its nose-up or nose-down pitch and its bank angle during turns.

Understanding the pitch and roll is essential for flying safely, especially in conditions where visual references may be limited, such as in poor weather or at night. By monitoring the attitude indicator, pilots can make informed adjustments to maintain controlled flight, ensuring that they do not inadvertently enter into an undesirable flight attitude, such as excessive bank or pitch.

The other options, while related to helicopter operation, do not reflect the primary function of the attitude indicator. Engine RPM, altitude changes, and airspeed changes are monitored by different instruments specifically designed for those purposes. Therefore, the correct answer focuses on the essential role of the attitude indicator in ensuring a stable and safe flight by displaying the helicopter's orientation.