Turn Radius

This formula gives the radius of the path an aircraft follows in a steady, level turn when the turn is coordinated, meaning the lift is tilted so it provides both upward support and the sideways force needed to curve the flight path. A higher speed increases the required turning radius because the aircraft has more forward momentum to bend, while a larger bank angle decreases the radius because more of the lift points sideways. The result comes from balancing the centripetal force needed for circular motion with the horizontal component of lift.

Use this when you need to estimate how tightly an aircraft can turn at a given airspeed and bank angle, such as in flight planning, maneuver analysis, or aviation training problems. It is most appropriate for steady, level, coordinated turns rather than climbing, descending, or slipping/skidding turns.

• Using indicated airspeed instead of true airspeed when the problem specifically requires true airspeed
• Forgetting that the bank angle must be in tangent form, not sine or cosine
• Applying the formula to non-level or uncoordinated turns where extra lift or side force changes the result