What is the radio reply frequency for a Class 1A transponder during testing?

The correct answer is that the radio reply frequency for a Class 1A transponder during testing is 1090 ± 1 MHz. This frequency is essential for the operation of transponders, which are critical components in the surveillance and tracking of aircraft. The standard operating frequency for secondary surveillance radar (SSR) transponders is 1090 MHz.

During testing, it is important that the transponder operates within the specified tolerance of ± 1 MHz to ensure proper communication and avoid interference with other equipment. This specification enables accurate signal transmission and reception, critical for maintaining safety and the integrity of AIR traffic management systems.

Understanding the specific frequency ranges and tolerances is crucial for A&P mechanics and inspectors, as it pertains to regulatory compliance and safety standards in aviation operations.