The “T” in HAT
The last letter in the HAT check acronym is T, for transponder set to altitude. I know that many of our vintage aircraft might not even have a transponder, and some of you that have one don’t like to use it. However I make a point of turning mine on if for no other reason than the fact that it might give a heads up of my presence to one of the many pilots who are zooming around in their glass paneled aircraft, hardly ever looking outside of the cockpit. With their TIS systems at work displaying all the transponder replies on one of their big glass
screens, hopefully my blip will appear there, and even if they don’t see me out the window, as they fly by, they will be aware of my company, and avoid me.
Another reason for insuring that the transponder has been set to altitude prior to takeoff, when departing into Class C or B airspace, is to avoid having departure control ask you to “recycle your transponder” (there nice way of saying: “turn it on, dummy”).