Instrument Flight Rules Practice Exam 2026 – Complete Test Prep

When making a standard rate turn to the left from a west heading in the Northern Hemisphere, the magnetic compass should indicate the approximate correct magnetic heading. This occurs because the compass responds to the aircraft's movement and the changes in magnetic field and inertial forces.

As you initiate a left turn, the compass will initially lag due to the centrifugal force acting on it which leads to a phenomenon known as "compass lag." However, this effect is generally transient.

In most situations, as you maintain the turn and the aircraft steadily rolls into the left turn, the compass will gradually begin to show a heading consistent with your new direction. Eventually, the compass aligns with the actual magnetic heading you're flying towards. This is why it can be said that the compass will indicate the approximate correct magnetic heading after a brief moment of adjustment.

This behavior is aligned with the known dynamics of magnetic compasses, especially in terms of their expected performance during turns in the Northern Hemisphere. The compass's tendency to show less accurate readings initially and then stabilize is an important consideration for pilots, but during the completion of a standard rate turn, it typically reflects the new heading closely.