No, We’re Not Asking About An Exotic Pet Bird…This Is About Your ATC Transponder

As a recreational pilot that flies VFR all the time and seldom uses any type of tower controlled airspace, it’s common to just leave your transponder set to 1200 and not think much about it. However, it’s important to understand that your transponder must still meet testing requirements even though you’re just boring holes in the sky. Let’s take a look at the transponder, its background, and why the heck it “squawk’s.”

As the story goes...In World War II, the allies invented an electronic device named “Identify Friend or Foe (IFF)” that would transmit a secret code when hit by a radar signal. This code would tell the friendly radar that this plane was a “good guy.” IFF got the nick-name of “parrot” because it responded to a radar interrogation and “talked back.” This led to the IFF reply being referred to as a “squawk.” The “squawk” terminology stuck with us and is still in use today.

For your transponders to be legal to use in any flight and in any aircraft, it must have been tested and inspected within the last 24 calendar months by an appropriately rated FAA aviation technician or repair station. This requirement holds true for all transponder equipped aircraft, including those certificated as experimental and special-light sport. We’ve even heard of an ultralight with a transponder, and it also falls under these rules even though the ultralight is not a certificated aircraft.

A common mistake made by recreational flyers is to think the transponder inspection is accomplished at the same time as an annual inspection. While there is nothing to prevent it from taking place every 2 years during the annual inspection, the aircraft inspector can sign the airplane off as meeting the inspection requirements without the transponder being tested. Don’t assume the annual inspection includes transponder testing.

Don’t expect to find the transponder inspection requirement in the airplane flight manual, maintenance manual, operating limitations, or ASTM industry light sport standards. The inspection requirement for transponders is listed in FAR 91.413. Without this testing and inspection you are not legal to activate your transponder, even if squawking the standard 1200 code for VFR flying.

In the early days of transponders, too many transponder equipped planes in a small amount of airspace would mess up the controller’s radar display. When this happened, the controller would start asking planes to turn off their transponders. It was not uncommon to hear them say, “Strangle your parrot.” That request made sense at one time.

(Image of Trig TT-31 transponder from file)

FMI: www.faa.gov/regulations_policies/