How does the radius of turn change for an airplane in a coordinated turn at a constant altitude?

The correct answer illustrates that when an airplane is in a coordinated turn at a constant altitude, maintaining both the rate of turn and the radius of turn is stable for a given angle of bank and airspeed. This means that for a specific combination of these parameters, the pilot can achieve a consistent turning flight path without making adjustments to maintain that turn radius or rate.

In a coordinated turn, the forces acting on the airplane, including lift and weight, establish a specific relationship between the turn's geometry and the aircraft's speed and bank angle. When the angle of bank and airspeed remain constant, the airplane will turn at a uniform rate and maintain a consistent turn radius, adhering to the principles of circular motion.

Although the rate of turn can increase with higher bank angles or decrease with lower airspeeds, in this context, assuming a constant bank and airspeed means that there will not be any changes in the turn dynamics provided these factors remain fixed. Thus, option A accurately captures the essential dynamics of a coordinated turn in stable conditions.

Understanding this aspect of aerodynamics is critical for pilots, as it helps them maintain control and predictability in their turns, enhancing overall flight safety and effectiveness in maneuvering the aircraft.