The growth of aviation prompts the need for all-weather solutions. One such weather-related problem is the icing of aircraft leading to dangerous consequences. Supercooled water droplets strike the leading edge of aircrafts as they soar through the clouds, this results in those very water droplets freezing and creating ice sheets on aircraft surfaces that must be removed. Some hazards of water droplet freezing and icing of aircraft surfaces, as Dr. Kamel Al-Khalil mentions in his report on deicing systems, are reduction in lift, increase in drag, and the disruption of aircraft airflow. As a response, in conjunction with companies and organizations such as NASA, COX Inc., the IDI company, FOX, Goodrich, Airtech, and AEROSPACE anti-icing and deicing technologies have been developed to combat this issue in aviation engineering. At the same time, the organizations and companies mentioned remain on a mission to innovate anti-icing and deicing technologies into the realm of hybrid technologies that account for mechanistic and user support.
To begin, a review of the major terms to be utilized within this writing is needed. Anti-icing targets the prevention of ice build-up on sensitive areas of aircraft during flight. What anti-icing technologies target is prevention of icing when icing conditions are detected either before or during flight. While De-icing systems target the removal of ice buildup on aircraft. Once ice accretion is detected deicing methods are utilized to remove the ice build-up. Some types of modern deicing and anti-icing technologies available are the following: Electro-Mechanical Expulsion Deicing Systems (EMEDS), Pneumatic deicing boots, Sonic Pulse Electro-Expulsive Deicer, The Electro-Impulse Method, and the Electro-Expulsive Separation System. Each of the systems mentioned will be discussed briefly herein.
The Two Major Categories of Deicing Technologies
The two important technologies available within the anti and deicing categories are modern technology Electro-Mechanical Expulsion Deicing Systems (EMEDS) and traditional techniques such as Pneumatic boots. The erosion surfaces for modern EMEDS are metal while the boots are elastomeric. The surface life of using EMEDS is for the life of the aircraft while boots last only a few months or years depending on aircraft wear. The drag increment induced by EMEDS is zero on the aircraft while boots cause a measurable increase in drag. Regarding the actual deicing performance, EMEDS can work efficiently with layers of ice as thin as 0.12 cm with no upper limit for ice thickness. Unlike EMEDS, Boots work best starting at 0.6 cm. The weight and cost of EMEDs are considered equivalent while for boots it is baseline. EMEDS, however, do require .7kW of power per 12 m span while boots require none.
Pneumatic deicing boots are the more traditional approach to deicing technology. Interestingly, unlike the modern technological uses of electromagnetic wavelengths or vibrations, the Pneumatic boots simply use a thick rubber membrane on the leading edge of aircraft surfaces that are most likely to develop ice and when ice build-up occurs the membrane is inflated which causes the ice buildup to shatter and come off the aircraft surface. Unfortunately, in cases of severe icing boots, over the years, have not proven to be sufficient for aircraft usability. Hence the introduction of more effective modern technologies such as EMEDS highlighted previously.
With EMEDS a high current electrical impulse is delivered to actuators which generate opposing electromagnetic fields causing the surface to flex and vibrate in a very high frequency causing acceleration based debonding of accumulated ice. The critical features cited with this approach to deicing is the efficiency with cost and weight of this method which also uses a fraction of the power that other similar deicing mechanisms require and is designed with an erosion resistant surface. The development of EMEDS has not only been helpful for commercial aircrafts but also smaller private aircrafts.
Other Modern Deicing Techniques and Technologies
Also known as SPEED, the Sonic Pulse Electro-Expulsive Deicer has evolved from the Electro-impulsive deicing method. SPEED uses acceleration to deice aircraft and was first used in NASA’s Lewis and ARPA’s SBIR program. Electrically operated, SPEED utilizes actuators in conjunction with a heater near the leading edge of the aircraft skin to shed ice into an airstream off the aircraft. SPEED can also work autonomously when IDI sensors are applied to the aircraft to continually provide support against icing for the aircraft. In addition, speed requires very little power consumption while not limiting aircraft performance. SPEED does, however, have icing impingement limits for its use which means that the deicing of surfaces can become limited after a certain point on the aircraft surface unless further actuators are installed to account for areas where the impingement limit occurs.
Another modern deicing technology is the electro-impulse method. Utilizing high voltage capacitors which activate coils right underneath the aircraft skin electromagnetic repulsive force results causing the scattering of built-up ice. There are negatives associated with this method including the risk of electromagnetic interfering which can cause the loss or malfunction of this system, and the loud noise created with this method. The electro-impulse method has only been tested and verified for use in aircraft tails and smaller aircrafts which limits its impact for commercial carriers.
Furthermore, Electro-expulsive separation system or EESS uses a combination of controllers and boots to shatter ice on aircraft surfaces. Utilizing two layers of conductors this system for aircraft deicing is a combination of the traditional and modern method approaches to aircraft deicing by utilizing boots as well as ice sensors. The major point to note with this method is that it can remove ice build-up of any thickness and works continually without the need for consistent user monitoring.
Other anti-icing and deicing technologies to note are the electrical heating of aircraft surfaces, Ultrasound Technology (UT), ice protection systems based on leaking fluid, and Shape Memory Alloys (SMA). These technologies are utilized by certain aircraft types today however, due to the lure of modern technologies such as EESS and SPEED, like Pneumatic deicing boots, the use for these technologies are less common. Technologies like SMA specifically can add surface tension or weight to the aircraft due to the onboarding of deicing fluids which decreases the efficiency of the aircraft. At the same time of note is the fact that technologies like the UT method are cost effective and environmentally friendly by simply using sound waves to break ice layers from building up on aircraft surfaces. There is a give and take for each of these methods however the use and implementation of them had been varied over different aircraft and flight specifications.
The Next Steps for Deicing and Anti-icing Technology
The primary point of innovation still left to complete is the combination of both deicing and anti-icing technologies to create a system which can both prevent and react to all-weather conditions. As Zdobyslaw Goraj states, this overarching effort is called the “DEICING” research project which will attempt to satisfy future industry demands on the subject of icing in response to some of the innovations highlighted above that are used today. The future of deicing technologies lies not just in the technologies presented above but also in alterative surface substances, materials, and innovations in aviation engineering which can reroute the issues faced by traditional aircrafts today as a result of icing.
To highlight how the future of aircraft deicing engineering is changing, as an interesting innovation, Katie Cottingham mentions in her report for the American Chemical Society, the development of self-lubricating organogels or SLUGs which promote a very slick aircraft surface which can prevent the buildup of supercooled water droplets during flight. The slick SLUG substance would be applied to aircraft surfaces and create a hydrophobic barrier preventing the build-up of ice on aircraft surfaces. The SLUG method is still in its formative testing years and will take some time to develop, however it is a deicing technology that can reduce the technical malware needed for aircrafts to prevent icing. At the same time this substance can be used for a plethora of aircrafts both large and small which removes the sizing issue often faced with deicing technology utility.
The hybrid approach and creation of deicing and anti-icing technologies is the continuation of what is to come with aircraft technology. While the development of EMEDS and other modern deicing technologies such as SLUGS aid in the progress of aviation innovation there still remains more to discover as the efforts behind aircraft performance in all-weather conditions continues.
- Al-Khalil, K. Thermo-Mechanical Expulsion Deicing System – TMEDS . New York, NY: AIAA conference, 2007. Print.
- Cottingham, K. “New material could make aircraft deicers a thing of the past ” American Chemical Society (2016): 1. Online.
- Goraj, Z. “an Overview of the Deicing and Antiicing Technologies with Prospects for the Future ” INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES 1.1 (2004): 11. Print.
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