Which instrument is required for flight under IFR?

Flight under Instrument Flight Rules (IFR) requires specific instruments to be on board to ensure safe navigation and operation in conditions where visual references are limited. One of these requirements includes having a clock with a sweep-second pointer or a digital presentation. This instrument is critical for pilots to accurately monitor time, which is essential for calculating rates of navigation, holding procedures, and ensuring compliance with specific time-based regulations during flight operations.

The presence of a second hand allows the pilot to measure time precisely, which can be used for tasks such as timing procedures designated by air traffic control or holding patterns. Accurate timekeeping is also crucial for navigation along airways and maintaining separation from other aircraft.

Other instruments may be useful for navigation and operations, but they are not strictly mandated for compliance with IFR regulations. For instance, while a GPS navigation system can be extremely helpful, it is not an essential requirement, as IFR can be conducted using traditional navigation aids. Similarly, while an autopilot can enhance flying capability and reduce pilot workload, it is not a required instrument for IFR. A radar transceiver, while beneficial in certain airspace, is also not a mandatory instrument for navigating under IFR. Thus, having a clock with the required characteristics is vital for the safety and legal