Which unit's failure during an IFR flight requires an immediate report to ATC?

During an IFR flight, the failure of the GPS unit requires an immediate report to Air Traffic Control (ATC) because the GPS is a critical navigation system that assists pilots in maintaining situational awareness and navigating accurately. When operating under Instrument Flight Rules (IFR), pilots rely on various instruments and systems to ensure safe flight, especially in conditions where visual navigation is not possible.

Failure of the GPS can significantly impact a pilot's ability to determine their position and navigate to their destination. Since modern IFR operations often depend heavily on GPS, its failure directly affects the safety of the flight, necessitating a prompt communication with ATC to inform them of the situation. This allows ATC to provide support, such as vectoring the aircraft or providing additional navigation assistance.

In contrast, while the failure of an engine on a multiengine aircraft does complicate the flight, it may not always require an immediate ATC report if the remaining engine is operational and can maintain safe flight. Similarly, while airborne radar is useful for traffic avoidance, it is not a critical system like GPS; many aircraft can still navigate safely without radar. The autopilot, although helpful, is not essential for controlling the aircraft, as pilots are trained to fly manually if necessary.