Which code is used for a situation where a pilot declares an emergency while being radar identified?

When a pilot declares an emergency while being radar identified, the appropriate transponder code to use is 7700. This code is universally recognized by air traffic control and indicates that the aircraft is experiencing an emergency situation.

The use of 7700 alerts controllers to the urgency of the situation and helps prioritize the aircraft's needs for assistance and safe separation from other traffic. In an emergency context, this code enables controllers to effectively manage the aircraft and ensure that necessary support is provided as quickly as possible. The declaration of an emergency could involve a range of issues, including engine failure, medical emergencies, or other critical situations requiring immediate attention.

The other codes serve different purposes: 1200 is the standard VFR (Visual Flight Rules) code, 7600 is used when an aircraft experiences radio communication failure, and 7500 indicates a hijacking. Each of these codes conveys specific information to controllers, but only 7700 designates an emergency declaration.