Avionics Cooling

wa4jr · Post by **wa4jr** » Fri Feb 07, 2003 5:01 pm

I am into my avionics refit now, having pulled the Apollo loran out as well as the old KX-145. Playing with my new KLN-88 on the test bench has been a blast. I have found that the unit gets quite warm after an hour or so. I am concerned that the unit will get even hotter in the panel on top of a KX-170B...especially during the summer flying season. Do any of you have an avionics cooling fan? With the KLN-88 running so warm, and a new KX-155 that may run warm as well, I purchased an Ameri-King AK-950 two port cooling fan. If you folks are running cooling fans, where do you mount it? I have thought the only good place is on the bottom of the glove box. The firewall has an insulation blanket that makes it difficult to work there, and I would not want there to be any chance of the fan ingesting insulation fibers and blowing into my radios. Also odd that the "approved aircraft" list that came with the fan lists Cessna 120/140 and then skips to the 172. The 180/185 is not listed either. I'll call and ask, but am not going to worry too much about it since any fan is better than no fan...and if it can go in a 120/140 it can certainly go in a 170. Thoughts and comments from those that have been there before???

doug8082a · Post by **doug8082a** » Fri Feb 07, 2003 5:19 pm

I could have sworn that George had posted something in the past about cooling a KLN-88, but danged if I can find it. If I remember right, he installed a small air scoop of sorts to provide ram air cooling for the unit. At least, I *think* I'm remembering this right......

Have a go a the search utility on the forum, maybe you will have better luck than I.

funseventy · Post by **funseventy** » Fri Feb 07, 2003 11:47 pm

My 54 B model has a scoop on the left side of the boot cowl. It is hidden under the side panel, but it has two tubes for hoses to attach and supply blast to two radios. I took mine out and patch the skin since I don't have any hot radios. I still have it I believe and it would be available if you wanted to return that expensive fan.

Kelly

zero.one.victor · Post by **zero.one.victor** » Sat Feb 08, 2003 1:25 am

My ragwing has a little scoop on the LH boot cowl also. Ihave never looked under the side kick panel to see what it does inside the airplane. Probably ought to,just for curiosity's sake.

Eric

funseventy · Post by **funseventy** » Sat Feb 08, 2003 1:38 am

And Eric, if you are not using it take it out. Its weight!! A light airplane comes from a lot of critical looks at the airplane and removal of all the unneeded.

K

doug8082a · Post by **doug8082a** » Sat Feb 08, 2003 2:00 am

Aha! Found it! But it wasn't on this site, it was on George's "other" site. Yes, folks, for those of you who may not be aware, we are not the sole recipients of our beloved moderator's wisdom. Alas, he has "another life"

, but I like to think that we hold a special place in his heart as fellow 170 owners.

I hope I'm not stepping on any toes by doing this, but here's the link to his post regarding the KLN-88 with a paragraph on cooling (and he does use a ram air scoop).

http://www.globalair.com/discussions/me ... orum&m=376

wa4jr · Post by **wa4jr** » Sat Feb 08, 2003 3:37 am

Thanks for the tips! I can't recall seeing any ram-air cooling provision on my '54 B but perhaps I am not looking in the right place. I know the C-150 my dad had was equipped with a little ram-air scoop on the side of the fuselage. Boot Cowl? OK...educate me. The boot on a British car is in the back, but I don't think the scoop would be back there. My bet is that it would be along side the aircraft just aft of the fire wall??? Was the ram-air scoop standard from the factory...if so I can find the patch and reverse engineer something. If that scoop is still surplus to your needs, Kelly, how about sending it my way??? The fan was $149 from Spruce...the price of a current database cartridge for the KLN-88!

doug8082a · Post by **doug8082a** » Sat Feb 08, 2003 1:45 pm

The scoop was added for avionics cooling. I don't believe a scoop was ever a factory option or provision. I think the KLN-88 can be cooled either by an air scoop or a cooling fan, but take this with a grain of salt as I'm definitely NOT an avionics guy.

Post by **GAHorn** » Sun Feb 09, 2003 8:23 am

The KLN88 requires 4 cfm of cooling air. The install manual specifies a cooling fan (by King, of course) and does not recommend a cooling scoop. (Presumeably there is no cooling air when stationary.) I installed my scoop on the left side in the location that many 172's had factory scoops. This places it in the prop slip-stream and assures air flow even sitting on the ground if the engine is running, and avoids adding another electrical device to the system. I also installed a piece of polyester screen material (found at hardware stores, called synthetic hardware cloth, for screen doors) in the cooling system to keep insects out.
The CRT display generates a lot of heat, and the KLN 88 should not be run without cooling airflow for more than a minute or two, or you'll shorten the CRT tube life.

funseventy · Post by **funseventy** » Mon Feb 10, 2003 3:57 pm

I will try to get to the airport tonight and see if I can find the scoop. I can also send you a digital picture of the placement of it. Mine was installed on the left side like George mentioned. Send me an e-mail so I have your address and I'll see about dropping this in the mail.

Kelly