Under what condition will the indicators of a magnetic compass be accurate?

The indicators of a magnetic compass will be most accurate in straight-and-level unaccelerated flight. This condition minimizes the errors associated with the Earth's magnetic field, the effects of acceleration, and the influence of the aircraft's banking during turns.

In a straight-and-level flight, the compass can accurately reflect the magnetic direction without interference from the aircraft's movement or aerodynamic forces. When the aircraft is in a turn, especially if it exceeds 30 degrees of bank, the compass may show a temporary turn error due to induced magnetic dip, which can lead to inaccurate readings. Similarly, during takeoff or landing, the varying airspeed and changes in pitch can cause the compass to fluctuate or lag behind the actual heading, further impacting its reliability.

Therefore, for navigation and ensuring accurate heading information, straight-and-level unaccelerated flight conditions are the ideal environment for the magnetic compass to provide reliable indications.