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Summertime Radio Troubleshooting

Two-way communication radios can be very frustrating, but there are some reasons that things get worse in the summertime.Two-way communication radios can be very frustrating, but there are some reasons that things get worse in the summertime. Here is your radio troubleshooting guide to help you transmit and receive with minimum problems.

It's Not The Humidity...
When you begin an airplane preflight inspection on a hot summer day, open the airplane doors and then, if you dare, look at the Outside Air Temperature gauge. If the airplane has been sitting out in the sun all afternoon that temperature gauge will read 130 degrees F or hotter. Most radios have an upper heat threshold of about 125 degrees, so your radios are already hotter than their maximum temperature -- and you haven't even turned them on, yet.

Keeping Your Cool
Airplanes all have some method of cooling the radios so that they will work properly and not get damaged by the heat. In some small airplanes the radio 'cooling system' is nothing more than a tube that leads from a scoop on the side of the fuselage to your radio stack. When the airplane radio “stack” gets taller (and, therefore, more expensive), a cooling fan is installed. You can check the cooling fan operation during the preflight inspection by turning on the Master Switch and listening for it. If you are not sure of its operation, consult a maintenance technician – but don't fly the airplane unless the radios are protected from the heat.

Remember: The radios can be the most expensive part of the airplane!

Failure To Communicate
Often the cause of radio failure is not the radio at all. There are many links in the radio communication chain and many parts to suspect. When troubleshooting a radio failure...

  1. Check the audio panel if the airplane has one. Especially with rental airplanes, the toggle switches and push buttons on an audio panel could be left in many different conditions. If the pilot before you did not use a headset, the toggle switches will be set on 'speaker' instead of 'phones.' It is good practice to 'preflight' the audio panel and have all the proper settings selected even before turning on the master switch.

    Note: Most toggle switches also have a neutral center position that will switch off everything. Accidentally bumping the toggle to neutral can be real embarrassing.

  2. If the radio is not working, place your thumbs on the lower corners of the radio box and push. The radio slides into the panel on a track. Only when the radio is completely pushed in will it 'plug-in' to both the power and the antenna connections -- that goes for the transponder, too.

    Inside Information: Even if the radio is not connected to the antenna, you probably will be successful getting a local radio check from across the ramp. However, after departure, you will *not* be able to transmit many miles to the controller.

  3. When transmitting, the microphone is your weakest link. It is great to have a headset, not just because it reduces noise but also because it has its own microphone. The airplane probably also has a manual microphone so you have redundancy. Headsets and push-to-talk switches can, themselves, create communication failure if they are not properly hooked up and functioning. Check the jacks and make sure all the obvious connections are secure.
Considering External Factors
The antennae can also be the cause of communication failure. Antennae must be grounded to the airplane to work properly and after years of enduring temperature extremes, these ground connections can crack. The absolute best (and cheapest) way to determine if a radio problem lies in the radio or the antennae is to switch the radio box to another airplane. Of course, they must be similar type radios that can slide out of one airplane and into another. Borrow a long skinny screwdriver from the technician and insert it into the small hole in the front of the radio to remove and slide out the radio. If the problem moves to the new airplane, then the problem is in the radio. If the radio works in the new airplane and the problem remains with the original airplane, then the problem is the antennae. You can spend a lot of money needlessly by sending a working radio to the shop when the problem was the antennae all along.

Defensive Measures
You should also 'preflight' the airplane's antennae -- this becomes even more important for instrument flight. Do you know which antenna goes to which radio?

  • Two-way radio communications radio antennae are usually on top ...
  • VOR/ILS antennae on the tail ...
  • An ADF has two antennae. One is a box that is mounted on the belly, and the other is the 'clothes line' that runs from the top of the fuselage to the top of the tail. Sometimes Glide Slope antennae are co-located with the VOR/ILS, but others are mounted in the front windshield – sometimes hidden by sun visors.
  • Transponder, DME and Marker Beacon antennae are on the bottom. The transponder antenna is often shielded by a plastic cover that looks like a big shark’s tooth on the belly of the airplane. Unfortunately, this is also where dirt and oil accumulate.
Hint: If a controller tells you that your transponder is not being received – clean off the shark's tooth and I'll bet it will start working again!

BOTTOM LINE: Get more familiar with what is attached to your airplane, the radio cooling system and all the links in the radio chain. Troubleshooting and preventive preflighting can avoid radio failures, dangerous situations, and unnecessary repair bills. Besides, the better you know your airplane, the better pilot you can be.

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About This Author:
Paul A. Craig is a Gold Seal Multiengine and Instrument Flight Instructor. He currently holds a total of 11 Flight Certificates including his ATP. Craig is a previous winner of the North Carolina and Tennessee Flight Instructor of the Year award, the NCVT Outstanding Teacher award and has served as the regional representative of the National Air and Space Museum. Craig is an FAA Aviation Safety Counselor and the author of eight books, including Pilot In Command, The Killing Zone: How and Why Pilots Die, and Controlling Pilot Error: Situational Awareness (all from McGraw Hill).
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