For the leading edges of aircraft's flight surfaces, there are a few more common deice and anti-ice methods available. What are the most common systems? What are the alternatives? Is there any research going into alternatives where new technology might provide better or more cost effective solutions?
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$\begingroup$ See: How do large airliners de-ice in flight and AOPA Aircraft Deicing and Anti-icing Equipment. Does it fully answer your question? $\endgroup$– minsOct 9, 2015 at 16:31
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1$\begingroup$ I'm familiar with that questions and I have that AOPA flyer in my CFI notebook. These questions cover the first part of my question, but I also wanted to put together a question that would result in an answer that also covered emerging technologies. The Wikipedia page for ice protection actually provides a good overview of existing, less-common and emerging technologies. I may use that as a basis for writing my own answer to the question. $\endgroup$– ryan1618Oct 9, 2015 at 16:37
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$\begingroup$ Okay. Just in case this is not already in your search results, a couple of ideas: How to De-Ice a Drone using Carbon Nanotubes, also Poison dart frog inspires new way to de-ice planes and older Zdobyslaw Goraj's article on the topic $\endgroup$– minsOct 9, 2015 at 17:01
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$\begingroup$ @mins Thanks for those references! $\endgroup$– ryan1618Oct 9, 2015 at 17:11
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3 Answers
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In general, deicing (removal of ice after it had formed) and anti icing (prevention of ice formation) methods used are:
Image from GKN Technology: Leading the way toward more efficient aircraft
- Mechanical which simply pushes the ice off the leading edges. An example is the pneumatic deicing boots, which is the oldest method used where an inflatable rubber boot is used for removing accumulated ice from the leading edges.
Source: quora.com
"Deicer (PSF)" by Pearson Scott Foresman - Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation→This file has been extracted from another file: PSF D-240001.png.. Licensed under Public Domain via Commons.
- Heating In large aircraft, the wing (and tail) leading edges are heated by engine bleed air (electro-thermal heaters in case of Boeing 787) for anti-icing and de-icing.
Image from Aircraft Anti-Icing Systems by Leslie Mehl and Annie Parsons
Chemical de-icing systems use dry or liquid chemicals designed to lower the freezing point of water (various salts or brines, alcohols, glycols); or by a combination of these different techniques.
Fluid de-icing systems which use de-icing fluid from a storage tank and fed through micro-filters to a number of porous metal distributor panels. As the fluid escapes, it breaks the adhesion between the ice and the wing and the airflow carries it away, creating the so called 'weeping wing'
There are a number of other de- and anti- icing methods are also available/under development, such as:
Electro-impulse method used high-voltage capacitors, which are rapidly discharged through the coils installed just inside the skin of the aircraft leading edge, resulting in a electromagnetic repulsive force (on the aircraft skin), throwing ice in all directions. However, the electromagnetic interference and structural fatigue associated with this method limits its application.
Electro- Expulsive Separation System An electric current runs through parallel layers of flat, copper ribbon. When a large pulse of current is passed, a repelling magnetic field is created, causing the upper conductor to jump less than a twenty-thousandth of an inch. The resulting high acceleration causes the the ice to break into tiny particles that fall from the airplane's surface.
Electro-Expulsive Separation System shatters and ejects ice from a wing model in a wind tunnel test from ipp.nasa.gov
- Electro-Mechanical Expulsion Deicing System, whose principle of operation is given by the developer as,
A microsecond duration high current electrical pulse delivered to the actuators in timed sequences generates opposing electro-magnetic fields that cause the actuators to change shape rapidly. This change of the actuator shape is transmitted to the erosion shield of the LEA causing it to flex and vibrate at a very high frequency. This rapid motion results in acceleration-based debonding of accumulated ice on the erosion shield.
Image from An Overview of the Deicing and Antiicing Technologies with prospects for the Future by Zdobyslaw Goraj
Ultrasound Some research is also going on into vibrating the wings using ultrasound to remove ice formed.
Shape memory Alloys have also been proposed to be utilized for deicing and anti icing, with their shape changing properties being used for ice removal when required.
Image from An Overview of the Deicing and Antiicing Technologies with prospects for the Future by Zdobyslaw Goraj
There has also been some research into usage of carbon nanotubes for this purpose.
answered Oct 9, 2015 at 17:48
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$\begingroup$ Do any of these systems address the problem postulated in American Eagle flight 4184 where supercooled water can freeze past the icing boots? $\endgroup$– TomMcWOct 9, 2015 at 19:58
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$\begingroup$ @TomMcW -- runback (or aft of leading edge) ice has not been seen as a concern with thermal anti-ice/deice systems so far; weeping wings are presumably protected by deice fluid running back along the wing upper surface. $\endgroup$ Oct 10, 2015 at 2:04
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This depends on the plane but generally speaking there are,
De-Ice Boots which work by allowing ice to build up and then they are inflated, thus cracking the ice off the leading edge.
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Heated Leading Edge Relatively self explanatory but it simply heats the leading edge either electrically or via hot engine bleed air.
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Weeping Wing (Chemical) is a technique used on some small planes where de-ice fluid is pumped through small holes in the wing leading edge to prevent the ice from building up. This presents 2 separate problems that the other systems don't suffer from. Aside from the weight toll you take for the system its self de-ice fluid is heavy and imparts another useful load toll. You also run the risk of using up all your fluid while in flight.
(source)
The FAA has a nice briefing on it you can find here which outlines all the various types of systems and the risks that come from icing. Their official list of icing prevention is
- Heating surfaces with hot air
- Heating by electrical elements
- Breaking up ice formations, usually by inflatable boots
- Chemical application
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There are four common forms, and not all are available to all aircraft:
- Heating the leading edge of all surfaces. This is done either by bleed air or electrically, and both will reduce engine thrust. Due to the high energy demand, electrical heating is mostly used on air intakes or propeller roots.
- Inflatable rubber boots. They are more economical, but must be operated correctly. If activated too early, the thin ice will not break off, if activated too late, the thick ice will prevent them from inflating.
- De-icing fluid: This requires fine holes in the leading edge through which a de-icing fluid is squeezed to break the bond between ice and structure. Some Beech Starships used titanium leading edges with laser-cut holes. Earlier systems, like that on the BAe-125, used sintered metal sheets which had tiny pores.
- Fly faster: Military jets don't need anti-ice, they use the stagnation heat generated by a higher flight Mach number. Generally, flying Mach 0.9 or above is enough to avoid trouble in light icing conditions.
Concerning future means: It is difficult to make predictions, especially about the future.
answered Oct 9, 2015 at 17:39