DA-40 Defroster

[smoss]

Flying a few days ago I had an interesting frosting experience. At 11,000 MSL or so, essentially clear sunny day, -13 C outside, flew through this tiny isolated wispy cloud and the front canopy instantly frosted over inside. Nothing on the rear windows, or even the rear sides of the canopy. Not sure if the moisture made it inside, or if the temp just dropped enough there to cause the frost over. I tried wiping it off with a rag, but it was hard frozen on there. Cranked up the defrost to full, but as others have noted, my pilot side defrost vent puts out less than the right side, and while the right side cleared up pretty fast, my side didn't budge. I hadn't thought to try and increase EGT to peak, it was at about 1370 range. Ultimately, I turned off the 'defrost' and moved the heat selector to floor, and then it cleared up pretty quickly. It seems the defrost, at least on my plane, really restricts the total heat output. I have checked the hose connections, etc. in the past and they are all fine. Anyhoo, I had a bottle of TKS in the back and was about to try wetting a rag with it and then wiping down the frost when it cleared up by itself. Has anyone ever tried to wipe down the interior with TKS to prevent/remove frost, and if so, how big of a mess is it to remove afterwards?

[Chris]

Flying a few days ago I had an interesting frosting experience. At 11,000 MSL or so, essentially clear sunny day, -13 C outside, flew through this tiny isolated wispy cloud and the front canopy instantly frosted over inside.

Strange experience! I haven't encountered that phenomenon, but I suppose the front canopy interior would be slightly colder than the rest of the interior surfaces due to the airstream, and the humidity increase and ambient temp drop going through the cloud was enough to create the frost. Essentially indoor freezing fog.

If you have a dry absorbant cloth towel, TKS fluid cleans up reasonably well, IMO. I don't think a paper towel would cut it, though, due to the viscosity. I don't think you'd want to apply it ahead of time since it would probably just bead up on the canopy.

[Colin]

TKS is rather unpleasant and no fun to clean up. I wouldn't use it in the air on the inside of the plane.

[smoss]

Colin, unpleasant in what way? I tried it on my airport fridge freezer frost, and it seemed to work well and wipe out easily afterwards, but then of course, I wasn't trying to look through it.

[Steve]

I would be careful about using TKS fluid inside the cockpit. These Safety Data Sheets can be somewhat overdramatic, but the components of TKS do exhibit acute and chronic toxicities:

https://www.cav-systems.com/wordpress/w ... t-2017.pdf

I would be especially concerned about residue remaining on the canopy interior surfaces, and being volatilized by the warm defroster airflow. Susceptible individuals could experience blurred vision, tearing, and corneal epithelial toxicity from exposure. It often doesn't take much of an exposure in a relatively closed environment to cause trouble. I had a patient who had significant corneal toxicity from anti-fog agent on the interior of his face mask while SCUBA diving. He had used this chemical many times previously without difficulty, but almost always diving in cold water. This time, he was in the Gulf of Mexico, used a bit too much, didn't rinse thoroughly, and I postulated that the warm water increased the volatilization of the anti-fog agent.

Just my 2 cents...

[Colin]

I found it a little caustic on my hands when I was filling once. And when I have cleaned it off the plane thinking it was water (I had run the FIKI but didn't realize at first how much keeps coming out after it is shut off and how the stuff sticks to the plane).

[jwx96]

Can anyone (Rich?) comment on the effect of a PowerFlow exhaust on the amount of cabin heat produced in a pre-2004 DA-40? I am considering upgrading when I do my engine overhaul. Thanks.

[Rich]

Can anyone (Rich?) comment on the effect of a PowerFlow exhaust on the amount of cabin heat produced in a pre-2004 DA-40? I am considering upgrading when I do my engine overhaul. Thanks.

The PF does produce hotter air for the cabin than the original exhaust system. The original system has an extra metal sheet around the muffler as a safety barrier against possible CO leaks. It has the effect of inhibiting heat exchange between the muffler surface and the intake air. I can't quantify the actual difference, though.

[Lance Murray]

Have you pulled the cover off of the panel and looked at the hose? Is the hose kinked or damaged? I am pretty sure that is the only difference between the let and right sides of the defrost. They come from the same manifold. Check the hose from end to end.

[Lance Murray]

Have you pulled the cover off of the panel and looked at the hose? Is the hose kinked or damaged? I am pretty sure that is the only difference between the let and right sides of the defrost. They come from the same manifold. Check the hose from end to end.