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Icing season is in full swing, which means you're seeing a lot of charts that look like this:
If you're not familiar with the chart, it's called a Current Icing Product (CIP). It displays icing severity in the blue areas - the darker the blue, the more severe the icing potential. It also means that if your plane doesn't have ice protection and your flight is supposed to take you through one of the blue areas, you're going to be grounded for awhile.
So how can small aircraft keep from icing up when the OAT drops below freezing? One of the more common ways is with something called a TKS system (Tecalemit-Kilfrost-Sheepbridge Stokes). It's sometimes referred to as a "weeping wing", but a TKS system protects a lot more than just your wings. But, we need to start somewhere, so let's talk about the wings first.
No, this wing leading edge isn't crying tears of joy because it got featured on Boldmethod. It's dripping an ethylene glycol based liquid out of thousands of tiny holes to prevent ice from forming on it. Here's how it works:
For aircraft certified for flight into known icing conditions (FIKI), TKS coats the the wings, horizontal stabilizer, vertical stabilizer, propeller and windscreen with anti-icing fluid.
It all starts with the fluid reservoirs. The reservoir tanks hold the TKS fluid. From there, a pump (or pumps) forces the fluid through ducting and to the titanium leading edges of the aircraft. The leading edges have thousands of tiny holes drilled in them, which let the fluid drip out at a controlled rate. Air flowing around the aircraft disperses the fluid across the leading edges, and rolls it back across the aircraft's surfaces, coating your plane in a protective film that won't let ice adhere to it.
But what about your prop and windscreen? Obviously, neither one of them are made of titanium with tiny drilled holes (it would be pretty hard to see out your windscreen if it were).
Propellers use something called a 'slinger ring'. The pump forces fluid through a tube and onto the inside of a grooved metal ring, right behind the propeller. Because the ring is spinning as fast as the prop, the fluid 'slings' through holes drilled in the ring, then through the tubes called discharge pipes, and out across the leading edge of the propeller. By providing a constant flow of fluid, the propeller stays coated in glycol, and ice can't adhere to it.
The last item is important for you to be able to see: the windshield nozzles. Two nozzles, similar to your car's windshield washer fluid nozzles, are placed at the base of the windscreen. When you turn the nozzles on, fluid sprays out of the nozzles and onto your windscreen. But in most cases, the windshield nozzles aren't necessary: your interior windshield defrost can get the job done.
There are several advantages to using a TKS system over booted or thermal deice/anti-ice systems, but two of the biggest advantages are reliability and fluid runback. Plus, TKS systems only have one moving part: the pump. And because the glycol fluid flows back across the wings, tail, and everything behind the propeller, it gives you better coverage than booted or thermal systems.
But there is one real disadvantage to TKS: time. Because you have limited fluid in your reservoir, you have a limited amount of time you can sit in the clouds. That amount of time varies by aircraft, and what flow mode you're using (TKS systems can pump a little or a lot of fluid, based on your needs). But it usually ranges between 1-3 hours of endurance, which is good, because you should be finding your way out of ice as soon as you can. Manage your time, and you're good to go. Otherwise, you could become an ice cube in the sky.
Colin is a Boldmethod co-founder and lifelong pilot. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed the development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.