Advantages of Aircraft Deicing and Anti-icing System
Aircraft that operate in weather conditions where ice is likely to form must be provided with ice protection technology. This protection may be in the form of anti-icing systems, or deicing systems. An anti-icing system prevents the formation of ice on the airplane, while a de-icing system removes ice that has already formed. In this blog we will focus on deicing boots and TKS fluid systems.
A de-icing system has two pertinent advantages. First, it can utilize a variety of means to transfer energy used to remove the ice. This allows the consideration of mechanical (principally pneumatic), electrical, and thermal methods. The second facet is that it is energy efficient, requiring energy only periodically when ice is being removed, with some mechanical designs requiring relatively little energy overall.
A deicing boot
is involved in removing ice from the exterior of an aircraft. It is a type of ice deterrent system that enables mechanical deicing while an aircraft is in flight. They are installed on the outer edge of a wing, where the likelihood to accumulate ice is much greater. A buildup of ice can significantly impair the aerodynamics of aircraft, leading to safety risks. Its design consists of a thick rubber surface that is then installed over a specific area of the wing, similar to a rubber membrane. As ice accrues, compressed air fills the boot, dislodging ice that has accumulated. From there the air travels through a pressure regulator, followed by a flow control valve. The ice is then blown away naturally and the boots are deflated to their normal shape. Deicing boots are operated manually or by a timer that is controlled by the pilot of the aircraft.
Anti-icing systems reverse the paradigm of deicing boots. They prevent the formation of ice continuously, resulting in a clean wing with no aerodynamic stressors
. An anti-icing system must have means of continuously delivering energy, or chemical flow, to a surface in order to prevent the bonding of ice. The typical thermal anti-icing system does this at a significant energy expense. The concept is not viable for aircraft that do not have the requisite excess energy available during all flight phases. An exception to this is the use of a chemical system such as the Tecalemit-Kilfrost-Sheepbridge-Stokes system (TKS).
TKS systems dispense an ethylene glycol-based fluid with a freezing point below minus 70 degrees F through porous titanium panels attached to the leading edge of the wing and empennage. The fluid is released through thousands of the laser-drilled holes, which are not much larger than the size of a human hair. As air flows over the wing and empennage, it disperses the fluid, coating the surfaces, and preventing the formation and adherence of ice. TKS systems also employ slinger rings to prevent ice accumulation on the propeller. As these metal rings spin right alongside the prop, they fling TKS fluid onto the propeller and consequently reduce the freezing point of the moisture in the area. In certain aircraft, nozzles also spray TKS fluid onto the windshield. Depending on the flow rate, TKS systems can provide anywhere between one to three hours of protection to allow for a safe exit from icing conditions.
Posted on August 19, 2019