When Must an Aircraft Have a Transponder? A transponder is not required unless an aircraft is operating: In Class A, Class B, or Class C airspace. Above 10,000 feet Mean Sea Level (MSL), excluding airspace below 2,500 feet Above Ground Level (AGL).
People Also Ask
You may fly without ADSB under the Class B or Class C shelf provided you remain outside of any Mode C veil. §91.225 tells you where you cannot fly. It says you cannot fly within the lateral boundaries of the Class B or C airspace or above the airspace.
Pilots can easily make a misstep by turning off their transponder, and there are very limited circumstances which allow a pilot to do so.” Civilian aircraft can turn off their ADS-B Out only if specifically instructed to do so by ATC, or if they are the non-lead aircraft in a formation flight, Duke said.
However, if you wish to operate in class A, B, or C airspace, or at an altitude of over 10,000' MSL, or within a 30 nautical mile radius of the primary airport in class B airspace, you will need a transponder and altitude encoder (commonly referred to as "mode C").
While you don't need an operable transponder to fly below a Class C shelf, you will need one to fly above Class C airspace. As you approach a Class C airport, you'll contact that airspace's approach control. Call ATC on the radio before you're in Class C airspace and make sure to tell them: Your position.
Regardless of weather conditions, an ATC clearance is required prior to operating within Class B airspace. Pilots should not request a clearance to operate within Class B airspace unless the requirements of 14 CFR Sections 91.131, 91.215, and 91.225 are met.
A Squawk 7700 indicates an emergency. This can be an emergency of any kind. Pilots may input it into the transponder themselves – or when instructed to do so by ATC. As a result, ground control will know that the aircraft is dealing with a serious issue and needs help.
In the 1900s, Hungarian physicist Theodore von Kármán determined the boundary to be around 50 miles up, or roughly 80 kilometers above sea level. Today, though, the Kármán line is set at what NOAA calls “an imaginary boundary” that's 62 miles up, or roughly a hundred kilometers above sea level.