Final answer:
The slowest airspeed to fly in clean configuration is the aircraft's minimum controllable airspeed or stall speed, which varies by aircraft. The drag coefficient is not directly related to the minimum speed but is a dimensionless quantity that represents resistance to flow and impacts fuel efficiency.
Step-by-step explanation:
The slowest airspeed that should be flown in the clean configuration is known as the minimum controllable airspeed or stall speed. It is the minimum speed at which an aircraft can maintain level flight without stalling. This speed varies for different aircraft and depends on factors such as the aircraft's weight, configuration, and the condition of the atmosphere. To determine the precise speed for a specific aircraft, one would reference the aircraft's flight manual or pilot operating handbook.
Drag plays a critical role in flight dynamics, affecting fuel efficiency and speed. According to the given information, drag coefficient is a dimensionless quantity that represents the drag force resistance an object encounters in fluid flow and can be assumed constant here. While an aircraft's drag coefficient doesn't directly tell us the slowest airspeed for a clean configuration, understanding drag is important for efficient flight operation. During periods such as the 1970s oil crisis, when fuel efficiency was paramount, understanding and optimizing for drag coefficients became more critical for vehicles, leading to regulations such as the 90 km/h (55 mi/h) speed limit on highways to save fuel.