R

Rainier Lamers

Well Known Member
A case of extreme behind the panel temperatures has come to my attention some time ago and as a consequence I have started investigating a few aircraft.
What led to this was a report by a V10 COM radio owner that reported that the radio was reporting internal temperatures close to 100 degrees C on a hot day (OK, really hot day - but you get them here often).
Well, no matter how well any electronics is designed - this kind of thing is extremely damaging and can only reduce the life expectancy of an electronic device. No matter who builds it or what it is.
This tends to happen on typical panels - closed at the top, often black material. No ventilation of any sorts, no airflow. Combined heat from instruments (no matter how little - it all adds up) warms the air behind the panel and that air rises and stays behind the panel. Additional heating from sun only adds to this.
Simply cutting a few slots into the top of the dash, filled with some nice mesh makes a dramatic difference to the temperatures behind the panel. A big difference. 20-30 degrees in cases. Simply by allowing the hot air to get out and drawing in cooler air from underneath.
Yes, installing a small 12V computer fan is certainly not a bad idea to keep the air circulating but in many cases just a few well placed slots to allow the air to circulate by convection is all that it needs.

Rainier
CEO MGL Avionics
 
This should not be a problem in a tip-up. But a natural flow cockpit vent would be nice when parked in the sun with the canopy locked.
 
Ranier,
It even happens in certified aircraft. The early S/N Cirrus were notorious for the Garmin stack going on the fritz esp the transponder. Easy solution was the aviation cooling fans that were less than $200 I believe. As you said a little moving air behind the panel goes a long way
 
Great point, Rainier. That's one of my biggest building regrets, since it gets really hot behind my panel and it would be a huge pain to cut holes now. I have an avionics fan ducted to my GNS-430 and Lightspeed ignition box, but it's still blowing hot air.

-Rob
 
Yes, it might be hot air but chances are that it is cooler than the air it is replacing - and that counts.

Rainier

RV10Rob said:
Great point, Rainier. That's one of my biggest building regrets, since it gets really hot behind my panel and it would be a huge pain to cut holes now. I have an avionics fan ducted to my GNS-430 and Lightspeed ignition box, but it's still blowing hot air.

-Rob
Click to expand...
 
Rainier,
this is a point that I have also thought of when my plane is tied down on the tarmac at Carson City or Bermuda Dunes. The interior temp is well over 100 as well as when in operation. I live in the NW and am hangared so it did not seem needed here, although it does just make good sense.

For the above, tied down on the tarmac and baking in the sun, scenario I may try the dash slots for the passive movement of air therefore avoiding temp buildup. Good point. Sounds like a no brainer now that you have mentioned it.
For use when operational it looks like a simple and practical resolution. It may save some $$ on the lifespan issue.

Thanks.
 
Better Cooling Can't Hurt

I flew a CT210 for many years. The plane had a full stack of King equipment that went from the bottom of the panel to the top- and the 210's got a very tall panel. At the top was the switch panel, which had the small metal flip toggles. Noticed right away that those toggles got so hot that you couldn't hold onto them if you wanted to. No problem as I was just "bumping" them to activate. No problem that is, until I fried one of the radios. lots of other problems before that. Had a remote avionics fan installed (type with multiple tubes going to the stack), and all of the problems vanished. Didn't fry another radio over the next 20 years, and couldn't feel ANY heat thru the toggles. Cheap fix.
Terry, CFI
RV9A N323TP
 
solar fan for hot days

This would be more for a plane parked in a hot climate, but I remember reading about a solar powered fan for cars that you rolled up in the window so you could still lock your car. The collector hung on the side of the window and powered a small 12v fan that circulated the air in the car.

It always looked like a good idea when we lived California, Placerville area. I never saw one in person, so I don't know how well they worked. I did a search and found them available at amazon. Since I am waiting for my empannage kit to arrive, I have no idea if one of these type of fans could be adapted to work in parked airplanes in hot climates. They are pretty cheap - $20+-. My guess is if you cut vents to the back of the panel, when you are parked after the flight, the heat from the panel will increase the heat of the cockpit. Having a secure way to vent that without using airplane power would be nice. Maybe a vent - hole could be cut in that the solar fan could sit over when needed and screwed shut when not.

Here is a link to the fans if interested.

http://www.amazon.com/Autocool-Solar-Power-Car-Fan/dp/B005NKO3D2
 
Heat issues

My 6A and RV-10 have both had their heat issues in spite of fans under the panel, gaps between radios, etc.

The Dynon's have failed to work a time or two and the 696 has had a few issues.

The 10 has the screen wire vent cut into the dash.

The multi-port avionics fans with ducts to each device seems to work well.
 
Most of the electronic devices used in radios and EFIS devices are "commercial grade". This is one up from "consumer grade" which, I think, few avionics manufacturers will consider.
Consumer grade devices are specified from 0-70 degrees C generally while commercial grade are -30 to +80 degrees C in most cases.
Aerospace qualified components tend to have similar ranges to commercial specs but are more resistant towards radiation (or at least certified to that - they are mostly commercial grade anyway). These are seldom used in our environment due to cost and difficulty in obtaining reliable supply. Also, no ready supply of modern devices.

This is however only one side of the story. More relevant is the PCB that holds the components and the soldering methods used. This is a huge field with many rules and specification levels for manufacturing standards.
Regardless of the standards used however, large temperature fluctuations will stress solder joints and current lead free technology (forced by the environmentalists) is still much worse than the old leaded solders in this respect. Modern LCC packages are perhaps the worst I have ever seen in this regard - but they are getting common as they are cheap to make.
Temperature fluctuations also stress PCBs - in particular through-hole plated connections and worse if multi-layer boards are used (4 or more track layers).
Lastly - connectors. Solderless connections. Often dissimilar metals are used and temperature and slight movement due to expansion can assist in creating oxides between the contacts, also helped by DC current flow (galvanic corrosion).

Bottom line: Temperature changes are bad. Also temperatures that are very low or very high are bad.

The easiest way to fix this is ventilation by whatever means behind the panel, either forced cooling or convection. This helps the electronics dramatically and is absolutely worth it. Nevermind much increased reliability for software driven systems which tend to be more sensitive to this kind of thing due to vast hardware complexity. Many "hangups" simply go away if temperatures are kept within reason and designed limits.

The idea to use a small solar driven fan has great merit and I like it very much. This would be most useful for typical hot climates like ours. We do not need a large airflow, just a little is quite enough.

Rainier
CEO MGL Avionics
 
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