By William W. Bennett, EAA 1246774
The trip was to be a vacation with my wife from McKinney, Texas (KTKI), in the Dallas/Fort Worth area, to Albuquerque, New Mexico (KAEG), for lunch and fuel stop, then on to Monument Valley, Utah (UT25). The weather looked to be fine for this mid-April trip. I had filed IFR from McKinney (KTKI) to Albuquerque Double Eagle II airport (KAEG) for the first leg.
My wife and I loaded the TB20 Trinidad and took off on runway 18. We were in the air at 8:49 a.m. CDT. ATC route had been filed as KTKI with KING3.SPS V114 CDS ACH RUINS ABQ KAEG at 8,000 (climb later to 10,000). It would take us about 3:45 to get to KAEG in the Trinidad.
The weather was forecast VMC with a layer of clouds in some areas. McKinney METAR reported calm wind and clouds broken 4,700. Takeoff in VMC from Runway 18. We were vectored by ATC over DFW Airport as usual for a western departure on the Kingdom 3 Departure Procedure.
All this went as planned, we have been on this route many times before. We could see multiple streams of airliners flying into DFW Airport and Dallas Love Field on ADS-B and out the window. Regional Approach (DFW TRACON) NE sector can be very busy. As we pass over DFW airport at 4,000 we were told to contact Regional Approach (DFW TRACON) NW sector.
We made the initial call, “Regional Approach, Trinidad 67RL level 4,000.” Soon after this is when the PTT (push-to-talk) switch started to go bad. It would transmit and block all radio traffic in DFW NW sector. I could see the “TX” message pop up and the sounds change in the headsets. Oh no, that is me!
At least the NW sector of DFW is not quite as busy as the NE sector. What is going on?
I could tug on the switch, and it would stop, but would start transmitting again a few minutes later. Of course, the DFW NW TRACON people loved me! I admitted to ATC the problem and said I was working on it.
As we flew, they moved us to the Fort Worth Center frequency and then I blocked them off and on. After twisting, pulling, pressing, you name it, I decided it was a 99% chance that it was the PTT switch, not the radio and not the wire to the radio.
We were now above an overcast and everything else was fine.
I am very glad we were in VMC above a layer and had the autopilot because I was busy in debug mode. As time went on, the problem of unintentional transmit got worse, blocking the frequency for miles around. We do have a good transmitter! At least as we headed west there was less and less traffic than in the DFW area.
Looking at possible solutions, it occured to me to use the “audio panel.” We have an older KMA-24 audio panel as shown below.
Top row of push buttons (Labeled 3 – 10) send sound to cabin speaker.
Bottom row of push buttons (Labeled 3 – 10) send sound to headphones (Headsets).
Knob at far right (labeled 12) sets which radio to transmit on. (Usually set to COM 1 or COM 2
Normally, I would set the knob 12 to “COM 1” for Radio #1. (Transmit and receive). Then the proper frequency in Radio #1.
When I want to listen to ATIS for example on Radio #2, I would press the button Labeled #5 (lower button) and it would receive transmissions from “COM 2” or Radio #2 and send it also to the headsets, thus, listening two Radio #1 and Radio #2 at the same time.
Temporary Fix to Receive:
My temporary work around for the stuck PTT, was to press “COM 1 Headphone button” (Labeled #4 lower), then move knob #12 switch to “TEL.” (TEL is not used on my airplane).
Now the PTT is sending a “transmit now” message to “TEL.” Therefore, not transmitting on the radio, thus not blocking everyone else. I can hear ATC (or whoever) because I have “receive” set to “COM 1.” Yeah! No blocking everyone else!
Temporary Fix to Transmit:
When I get a call and need to respond, I switch the #12 to “COM 1” and speak as the PTT was stuck on. (I press the PTT too as it is scratchy on/off unless I press it fully). As soon as I finish transmission, I return #12 to “TEL.”
This is so much better! We continue our flight, and we don’t mess up everyone else along the way.
Radio #1 is an Avidyne IFD 540 which displays “RX” and “TX” message. It also notes stuck mike and disables transmit after 30 seconds. When it is on/off/on/off it restarts the timer, so I never hit the 30-second cutoff.
The use of the KMA 24 works, but it is not ideal. The intercom in the airplane does not work well with the TEL selected. Not a big deal in this case, but less communication with others on the airplane. Possibly I could have turned off Radio #2, switched to COM 2 rather than TEL, and the intercom would have worked. I did not test this.
Other Options:
- Use the hand-held mike and hope it would override the PTT, mine did not.
- Pull out my handheld radio, it is battery-powered and has limited range and limited life.
- Stop at a nearby airport. What services would they have? This area, while it has airports, may not have very many repair shops?
- Go back to my home shop but that would have put us back in the DFW area, though I could have done that VFR once below the cloud deck.
- Continue on as we were going to a GA-friendly airport with lots of services.
- Use a multipurpose tool to disassemble the switch. I did not as I decided that was a bad idea. It might work, might make it worse.
- Continue with the workaround, using the KMA24 being the transmit switch.
- Continued to look for other options. The Foreflight document search of the POH and Avidyne manual was fast and easy, but found no better solutions in this case.
As we reach the Albuquerque area, I’m quite happy to be landing at an airport with services. Maybe I would be able to get the PTT repaired while there. We are transferred to Albuquerque Approach, then Double Eagle II Tower for a visual approach and land on runway 4 at 12:35 p.m. CDT which was local 11:35 a.m. MDT. All is well!
We are marshalled into parking space next to Bode Aero Services FBO. The Bombing Range Café, located upstairs at the FBO, is closed on Monday. The avionics shop on the field has gone to lunch. We took the crew car to get a sandwich as well and on the way I called my mechanic back home in Texas about the stuck PTT switch. He suggested we try some contact cleaner on the switch. We purchased some at an auto parts store next to the sandwich shop.
Even better news, upon returning to the airport, the avionics shop guys were back. I walked over to Air One Systems and spoke with David Espinosa, the owner. Of course, he was quite busy, but he took the time to look at our Trinidad. He said the contact cleaner might work, but said it would be better to put in a new one. The spring in the old one looked to have given up so not sure the contact cleaner would have done any good. He had a PTT in stock and installed and tested it in about an hour! A huge thank you to Air One Systems and David!
Meanwhile, we had some coffee at the FBO and watched a few airplanes take off and land. The repair was completed, with only a slight delay, and we were now ready for the next leg to Monument Valley (UT25).
I usually plan trips to stop at airports with services, both ATC services and mechanical services. I know some pilots like to pick stops based solely on fuel price, that is fine but not what I do. Some of those low-cost fuel airports have little in the way of services if needed. Picking airports with more services has worked out well for us over the years.
What is the most-used switch on your airplane? Master switch? No. Electric fuel pump? No. Landing gear lever switch? No. If you have a radio, it is probably your push-to-talk switch (PTT). No pilot likes radio problems! Usually when we think about radio issues we think radio failure — NORDO, light signals, etc.
My airplane is a SOCATA TB20 Trinidad, the radio equipment usually works very well. There is nothing unusual about the radios or how they are installed. The culprit on this flight was unexpected. The PTT never displayed symptoms until it went bad.
Post trip note: Our trip on to Monument Valley, Grand Canyon National Park, Bryce Canyon National Park, and Zion National Park went well. We had a great time. Upon our return to Texas, I sent a gift basket from Berdoll Pecan Farm to David for his kind assistance to a pilot in need away from home.
I hope you never have a stuck PTT or other radio problem, but if you do you may want to think about your radio panel configuration in your airplane and see what could work for you if a PTT does get stuck one day.
William Bennett received his private pilot certificate in 1988, he now has over 1,100 hours flying and an IFR rating. He has owned his SOCATA TB20 Trinidad for about 14 years. He is the author of the book, Flying the SOCATA Trinidad, Tobago and Tampico.