Yesterday, exactly one week after receiving my instrument rating, I filed an IFR flight plan from Gaithersburg to Lancaster, intending to give this “single pilot IFR” thing a try. It was a severe clear kind of day, so there wasn’t going to be any actual attitude instrument flying; instead, it was a chance to test out my ability to obtain, follow and understand clearances and other important elements of the instrument flight rules system. Plus, it was a great opportunity to take a solo flight under IFR – something you don’t get to do until after your instrument rating is complete.
It was also an opportunity for me to experience my first true in flight systems failure.
En route to Lancaster, Potomac Approach reported to me that my altitude readout had stopped reporting, and asked me to recycle my transponder. This was not the first time this had happened; it happened a few times before that and always resolved itself after turning the transponder off and then back on. However, in this case, the Mode C readout continued to fail and return intermittently, for the whole flight.
Altitude readout is important because IFR separation is dependent upon knowing the altitude of each aircraft. It’s especially important in controlled airspace (at the time I was well within the bounds of the Baltimore Class B airspace), since planes are closer together and controllers need to have every inch of available airspace. Potomac advised me to have the unit checked, and I promised that I would. Though a transponder failure is a problem, it’s not an emergency, and I continued on the flight being watchful of my altitude.
Arriving in Lancaster, I stopped into my avionics shop and discussed the problem. Though they couldn’t resolve the issue right then and there (right parts, nobody to do the work), they were able to offer me some suggestions. Knowing that the outside air temperature was the likely cause of the failures, I picked up my IFR clearance to return and headed out, with no failures between Lancaster and Gaithersburg.
The complexity of airplanes makes it increasingly likely that some component will fail on any given flight, which is why the majority of instrument training is not training for what to do when all systems are working, but what to do when systems are failing to work properly. It’s why we study partial panel operations, why we shoot approaches without the use of our GPS, and why we practice for comms and electrical failures.
Next Thursday I’m scheduled to head back to Lancaster to have the transponder repaired. A new encoder will solve the problem, and keep me in the skies safely.