Which instrument is mandated by FAR 91.205 for VFR flight?

The airspeed indicator is mandated by FAR 91.205 for VFR (Visual Flight Rules) flight because it is essential for pilots to monitor how fast their aircraft is moving through the air. This instrument plays a crucial role in ensuring safe and controlled flight, particularly during takeoff, landing, and while maneuvering. Despite the importance of other instruments, the regulation specifically identifies the airspeed indicator as necessary for VFR operations, highlighting its critical role in maintaining awareness of the aircraft's performance and adherence to safe flying speeds. Other instruments listed, while useful in VFR flight, are not required by the regulation, reflecting that the airspeed indicator holds foundational importance in flight safety and pilot decision-making.