Capflyer

Capflyer

Well Known Member
Question for the avionics techs out there.

Seems a problem from last summer has re-appeared this summer. When it gets hot out my GTX-327 transponder stops transmitting my squawk & altitude. This is a huge problem for me since I fly from an airport in the DC SFRA. Last week I had trouble getting back in to fly home.

Installing an avionics fan is a little overkill but I can easily install a blast tube off of my cabin vent line. The question is, where should I end it to blow the cooling air on the transponder. I'm guessing on the back where it looks like the tray back plate is a huge heat sink but just want to be sure.
 
I'm no expert but the install manual says forced air would be best if aimed at the rear heat sink.
 
Summer heat vs avionics

On my 6A, the Dynon has gotten so hot it wouldn't start up until airborne. That was when it was canopy closed on a 100 degree day. I have a computer fan blowing under the panel.

The RV-10 Garmin 530 would not start up on the ramp in Little Rock this week. Plane on the ramp, doors closed. Passing 3000', it started. Same computer fan under the panel.

Garmin 696 has sputtered a time or two also.

Plan: going to install a real avionics fan when 1" ducts to each device.

It's hot!

__________________
From Garmin's Newsletter. . .

It's a good time to go over the care and ongoing maintenance of these units so that you can maximize
the flight hours and reliability of your GNS series product.
First and most importantly for keeping the unit looking good, make sure that you only clean the
display with non-ammonia based cleaners or a very mild detergent using a clean, lightly
moisturized cotton or micro-fiber cloth. There are anti-reflective coatings on the display that will
easily display finger oils and other debris. These coatings can come off if the display is not
cleaned properly, reducing the viewability of the unit.

Secondly, be sure that you have good forced-air cooling. While the GNS 530/430 series units
have a very wide operating range and can function without it, forced-air cooling will add years of
life to any of your avionics equipment. It is very rare to find an aircraft that does not have some
type of forced-air cooling installed. To check your cooling system, turn on your avionics and listen
for the cooling fan before you put on your headset. Depending on the aircraft, you may find
additional kits available to increase the airflow behind the avionics stack.

Another key item to watch is the quality of the air coming into the unit. In-line air filters
incorporated in your avionics cooling system can help to reduce dirt and dust contamination in
some operating environments.

“Ram Air” cooling is never acceptable for avionics as it allows
moisture and contaminants direct, unfiltered access to your avionics and will actually reduce the
overall life of the units. See your local avionics shop for air filtering and cooling options for your
aircraft.
 
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Cooling

I was told by Stein that the Garmin stack gets HOT! A multi port fan did the job, lucky for me there was an extra port, because the 696, will shuts down when it overheats. A blast tube on the back and the 696 problem was solved as well. Once again thank you Stein.
Hope that helps.
 
The Garmin GTX-327 has a 1" dia tube flange built into the rack case. All you need to do is connect/clamp your 1" SCAT tube to this flange.

The install manual indicates that forced air cooling reduces the high heat induced reduced PRF (Pulse Repetition Frequency) in areas where very high traffic is involved. This keep the unit from overheating.

The TxPonder was designed to handle a constant 450 PRF, short periods of 1200PRF. Longer periods above that will cause the unit to go "overspec" and the PRF will be reduced.
 
Capflyer said:
but I can easily install a blast tube off of my cabin vent line. The question is, where should I end it to blow the cooling air on the transponder.
Click to expand...

Make sure you have a way to block the air in the rain, or you'll be injecting water into the avionics.
 
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