The Sounds of Silence - Part 2

This last weekend, Thing 1 was unusually free, there not being a football game scheduled (she is in the band).  We had promised Thing 2 a trip to Sea World if she scored all A's and B's throughout 6th grade, and since she delivered, we had to as well.  The stars were aligned for a trip to San Antonio.

At 3:30 Friday afternoon I arrived at the airport, and having pre-flighted the Bonanza, taxied over to the fuel pumps for a fill up.  At 4pm, Sally arrived with Thing 1 and Thing 2, and we blasted off through the muggy afternoon, IFR with a clearance via Waco and Austin VORs.  Once south of Love Field, I was cleared up to 8,000, which put us in a layer of clouds, so I requested, and was cleared to continue the climb to 10,000ft.  With a GPS ground speed of 150 kts (17 knot headwind), we landed and shut down the engine just before 6pm. The FBO (Millionaire) had the rental car on the ramp, and helped us load it up, while I made arrangements at the desk.

After spending the whole day at Sea World, we arrived back at the FBO at 6:30pm. While San Antonio had high overcast, a check with Flight Service and looking at the radar, showed a line of strong thunderstorms near Waco, and heading north east towards Dallas.  I didn't fancy single pilot IFR at night under those conditions, so we made a reservation at a local hotel, and spent the night.

Early the next morning, San Antonio was wet.  Over half an inch of rain had fallen at the airport, and the ceiling was 300 feet.  Dallas was clear, and the cloud overcast thinned out around 50 miles north.  With my clearance in hand, I taxied to the active runway and ran my checks.  I switched the tower frequency, and then I noticed that my transmit light was flickering, and the #1 radio (a Garmin 430W) was also showing "Tx", which meant I was transmitting non-stop.  I switched radios, and found that the same thing happened with radio 2 - I had a stuck microphone transmitter switch.

Of course when transmitting, you can't receive.  In a recently well publicized case, two Southwest Airline pilots had a stuck mic, and transmitted their innermost and not very flattering thoughts to the whole world.  I don't think I said anything bad, except to insist that Thing 1 should wear her headset for take off.  I may have blocked the frequency for a few minutes.

I transmitted in the blind that I had a stuck mic, and was returning to the FBO, but I actually just went to the nearest, Landmark.  There they tried to find a mechanic, but being Sunday, no-one was working and no-one answered the on-call phone number.  So I decided to rent a car and drive home that day, so that the girls would not miss school, and come back the next day.  In the meantime, I asked them to put the Bonanza inside so that it could dry out, if the rain and damp was the cause.

The next morning, I got up at 5am and drove the 5 hours to San Antonio airport.  After returning the car and paying the hangar fee, I got into the Bonanza and turning on the radios.  I found I still had the same problem, but that if I put the audio panel intercom switch into "isolate", effectively turning off everything except my own headset and mic switch, the problem went away.  So I departed VFR, and arrived at my home airport 1 hour and 45 minutes later.

Once on the ground, I set the audio panel selector to first "crew" and then "all", and had no problems with a stuck mic.  I suspect that I was correct - the heavy rain and/or 100% humidity caused either the audio panel, or the co-pilot's push-to-talk switch to short out.  Getting into the dry air and running the radio stack and cooling fans dried it out.  So it was in the end fortunate that no mechanic was available early on Sunday, I saved a lot of money.  I did have to rent a car for a day and spend money on about 10 gallons of fuel each way, but now everything and everybody is where they are supposed to be.

Any lessons here?  Not really, I had a stuck mic and I found it on the ground before it became a big problem.  I made the right call in not attempting the night IFR flight on a stormy evening.  I spent $140 on a hotel room, $30 for a car and $60 for gas, plus $50 for a hangar rental.  But the first hotel was free, thanks to frequent traveler points, and it's only money.  Better to be safe, and alive to pay the bills, than to be sorry.