Which airspace requires a 4096-code transponder with encoding altimeter as part of its equipment requirements?

• A. Being in Class A, Class B (and within 30 miles of the Class B primary airport, and Class C)
• B. Any Class E airspace
• C. In all Class G airspace
• D. Only in military airspace

Answer: (A)

Radar-based air traffic control relies on transponder data, and having a transponder that can squawk a discrete 4096-code and report altitude allows ATC to identify your aircraft and know how high you are. This combination is required in airspace where ATC separation and surveillance are needed: Class A, Class B (and the portion within 30 miles of the Class B primary airport), and Class C. In these areas, the altitude-encoding transponder helps controllers manage traffic safely, especially in busy environments or where precise altitude information is essential. Outside of those areas, such as most Class E and Class G airspace, an altitude-encoding transponder isn’t universally required for VFR operations.