Time for TKS to Coat Wings

[MichaelM]

I have been using the TKS system at least once a month. On a recent trip, I had used it on the outbound flight. About 10 days later, I was on a long trip and was just going to run it for a few minutes, since I thought that plane might be sitting for a while. It took about 15 minutes for me to get the TKS system to actually wet the right wing all the way to the edge. I was getting nothing on the right wing for about 7-10 minutes.

I was getting low-pressure warnings (as if often the case). All in all, it took about 15 minutes of switching pumps, hitting the windshield button multiple times, moving between normal and high, flipping the big alternate button, etc. To get the system fully on and working. Burned through about 4L over about 15 of TKS fluid before all surfaces were actually coated.

This seems unreasonable for a system that is being operated regularly.

What are others experiencing?

[ememic99]

I can give you data for DA42 only. If turned to MAX, both wings are completely wet all the way to the winglet until the end of MAX session (2 min). If turned to NORM, it takes few on/off periods to get the same result. HIGH takes some more time than MAX to get the same result - approximately 5 min.

[Chris]

Is this the first time the right wing was slower to get wet? I'm not sure if the plumbing is completely symmetric or if the LH wing has a shorter path from the pump(s). My DA42's RH wing might take a little longer than the LH wing, but not that much longer.

I've started using the HIGH setting (not MAX) for the first couple of minutes to get the system primed up before switching to NORM. That seems to reduce the variability and long wait times. I think NORM only runs the pumps on a 25% duty cycle, so you can imagine the fluid taking two steps forward with the pumps on, and one step back as the pumps cycle off for 90 seconds (IIRC).

It's also possible that one of your pumps isn't working as well as the other. Consider tracking which pump you use and how long it takes to get fluid to the wings whenever you use it to see if there's a pattern.

[Boatguy]

My experience is like Michael's, lots of low pressure warnings if I start up on Normal. Chris is right about the duty cycle and that explains the long start up time in Normal. Emir's approach of starting in Max, then dialing back once they are coated sounds wise.

[ememic99]

DA62 has longer wings, so obviously more work to be done. I don’t know if the pumps are the same as in DA42.

[thommy152]

Low pressure warning lights and about 5 mins before total coverage of the wings. I’ll turn it on well in advance of icing so everything is primed and ready when needed.

[ememic99]

I’m puzzled with this low pressure warning. Is it normal/expected behavior or it happens just occasionally on some aircrafts?

[Pehu]

For my DA62 it also varies from time to time. Two days back I flew and all panels worked nicely as should be. Today, on return trip, left wing was missing couple of panels. Some days its been vice versa on wings.

When I initially got the plane, I tried to run all panels wet and once it took a looooooong time. And I was still missing one panel. I used 20-30 litres of fluid. The next day, it worked instantly, all panels were wet.

I think there might be some "blocking" and just pushing TKS fluid in will melt it shortly. Nowadays I am not worried about missing a panel when doing the runs, it will work the next day. The same goes for the front TKS pray, sometimes it trickles and the next day it's gushing as it should be.

TKS works in mysterious ways.

[Pehu]

I’m puzzled with this low pressure warning. Is it normal/expected behavior or it happens just occasionally on some aircrafts?

It tends to happen sometimes. Then it goes away. But panels work.

Also keep in mind if OAT is over 20C this will happen too. It's mentioned in the plane's manual. Warm fluid makes this happen.

[Boatguy]

When I initially got the plane, I tried to run all panels wet and once it took a looooooong time. And I was still missing one panel. I used 20-30 litres of fluid. The next day, it worked instantly, all panels were wet.

At the risk of thread drift, how do you deal with the dripping TKS fluid in the hangar for weeks after their last use.