A New Approach to Ice Protection
Pneumatic de-icing systems have been the standard for general aviation aircraft for many years. Their utility and reliability have been taken for granted by pilots and maintenance personnel alike. Yet, the boots require a level of maintenance that is sometimes undesirable.
A company cal
led Aerospace Systems and Technologies, Inc. (ASandT) began introducing an alternative to general aviation aircraft in 1987, and as the company gains a foothold in the industry, you (the technician) may be called on to repair, service, or troubleshoot it — so take note!
The system, which it calls TKS, achieves ice protection by mounting laser-drilled titanium panels to the leading edges of the wings, horizontal and vertical stabilizers. Secondary fairings or structures such as wing lift struts can be protected in a similar manner. Propellers are protected with fluid slinger rings, and windshields are provided with spraybars.
The basic system is not really new. According to TKS, fluid ice protection started in the 1930's as companies experimented with methods of introducing de-icing fluid at the leading edges of wings. The TKS system was first developed during World War II as a method of providing ice protection for armored leading edges. The concept evolved through the 50's and into the early 60's when TKS ice protection was applied to the HS-125 business jet. Since then, every 125 produced has been equipped with TKS ice protection. Then, in the early 80's, laser-drilled panels were developed and first applied to the Cessna Citation SII as standard equipment.
What is new is the introduction of this systems to the single engine, general aviation market. TKS received its first STC for the Beech Bonanza in 1987. Since 1987, a handful of additional STC have become available to customers .
According to ASandT, TKS ice protection offers a level of ice protection unsurpassed by any other method. It has the major advantage of providing anti-ice capability, as opposed to de-ice capability. The end result is an ice protection system that keeps ice off of the aircraft, maintaining aircraft performance in the icing environment. This level of protection, coupled with the ease of use of the system, provides effective, simple ice protection.
The TKS ice protection method is based upon the freezing point depressant concept. An antifreeze solution is pumped from panels mounted on the leading edges of the wings, horizontal and vertical stabilizers. The solution mixes with the super-cooled water in the cloud, depresses its freezing point, and allows the mixture to flow off of the aircraft without freezing.
The system is designed to anti-ice, but it is also capable of de-icing an aircraft as well. When ice has accumulated on the leading edges, the antifreeze solution will chemically break down the bond between the ice and airframe, allowing the aerodynamic forces on the ice to carry it away. This capability allows the system to clear the airframe of accumulated ice before transitioning to anti-ice protection.
A valuable side-effect of TKS ice protection is the reduction of runback icing on the wings and tail. Once fluid departs the panel on the leading edge of the surface, it flows aft, over the upper and lower surfaces, and departs the aircraft at the trailing edge. This runback effect keeps ice accumulation in check aft of the panels, from runback or from impact of larger water droplets. This side-effect is a positive benefit in today's environment of concern for ice protection during large droplet encounters.
A full tank of ice protection fluid provides up to 2.5 hours of continuous ice protection.
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