What angle should you place the bearing pointer on the compass to correct back to the arc when one mile outside the assigned arc?

The bearing pointer on the compass indicates the aircraft's current heading in relation to the desired course. When you find yourself one mile outside the assigned arc, you need to make a correction that accurately brings you back toward the arc line.

Setting the bearing pointer 20° above the 90° index is typically the recommended adjustment because it strikes a balance between making a significant enough course correction without oversteering. This increment allows for the necessary adjustment to redirect the aircraft effectively without causing excessive movement that could lead to overshooting the arc.

In navigation, precision is key, and this 20° adjustment provides a calculated yet efficient means to return to the intended flight path, taking into account the dynamics of the aircraft and the factors at play when approaching the arc. Making smaller adjustments at this point is also critical, as it allows you to maintain smooth control and avoid abrupt maneuvers that could lead to additional corrections and complications.