Certified Flight Instructor - Flight Instructor Airplane Practice Exam

Which altitude range requires an altitude reporting coded transponder?

1. All airspace below 10,000 feet MSL

2. From the surface to 18,000 feet MSL

3. At and above 10,000 feet MSL below Class A floor

4. Below 5,000 feet MSL in Class B airspace

The correct answer is: At and above 10,000 feet MSL below Class A floor

An altitude reporting coded transponder is required in controlled airspace to accurately relay an aircraft's altitude information to air traffic control and other aircraft. This is particularly essential for maintaining safe separation in busy airspace. The specific requirement for altitude reporting transponders applies at and above 10,000 feet MSL, but this does not extend to all airspace in that altitude range. Instead, it particularly applies below the floor of Class A airspace (which begins at 18,000 feet MSL). Thus, while an altitude reporting transponder is indeed necessary when flying at and above 10,000 feet MSL, it is particularly highlighted in this context as a requirement for the airspace below the Class A floor. Other altitude ranges mentioned do not uniformly require altitude reporting transponders in the same manner. The airspace below 10,000 feet MSL, for example, does not generally necessitate a transponder unless specified, and while a transponder is required in Class B airspace, the altitude reporting aspect is not specifically tied to those lower altitudes. Hence, the answer points to the correct operational rule regarding altitude reporting transponders concerning Class A airspace.