D. Patrick Caldwell on The Joys of Flight

I've spent a little time in some older airplanes. Sure, I really like all the fancy avionics in newer airplanes, but sometimes if I'm just hopping over to KAHN for one of those awesome burgers at Clocked, I don't need to spend 150 bucks on a DA-40 when I can rent an old warrior for 95. In fact, that trusty old airplane has taken me on several 100+ mile cross countries. VFR or IFR, it's a great plane and it's fun to fly.

In fact, I don't really notice much of a difference insofar as functionality is concerned. On a long IFR trip, I'm still just keeping the needle centered whether I have a Garmin 480 or an old analog radio. There is, however, one major difference that's worth mentioning. A little extra care must be taken when working with analog transponders.

As you probably recall, general aviation aircraft use the transponder codes 7500, 7600, and 7700 to indicate various emergencies. When we tune these in and the Air Traffic Control Radar Beacon System issues a Mode A interrogation, our transponder shoots the signal over and any scope that is covering your area will issue an alarm. As I'm sure you can imagine, controllers don't really care much for false alarms.

That's why on the newer fancier digital models, your new transponder code doesn't take effect until you enter all four digits; however, on the older analog models, if you receive an interrogation half way through setting your transponder code, you could wind up inadvertently squawking an emergency code for several minutes depending on frequency congestion.

Keeping in mind that 7500, 7600, 7700, and 7777 are reserved for emergency uses, we should do our best to avoid inadvertently squawking these codes. For example, if you're currently assigned 6777 and are told to squawk 0325, you should tune the 325 in before tuning the 0. Why? Well, if you're spinning that knob just as fast as you can from 6 to 0 and the Mode A interrogation comes in during that split second when your first digit is at 7, then you'll have a lot of explaining to do when they ask why you're involved with a military interception. Another alternative is to turn the first knob away from 7 (i.e., 6-5-4-3-2-1-0 rather than 7-0).

Tuning the last 3 digits to get out of emergency range before rotating the first knob will keep you from making some embarrassing mistakes. If, for some reason, you have to go from say 5500 to 0700, you might just consider turning the knob the long way just to avoid transitioning through the 7000 range.

Have fun. Be safe. Happy Piloting.