Article: 9084 of rec.aviation.misc Path: newshost.ncd.com!ncd.com!olivea!nntp.msstate.edu!gatech!swrinde!cs.utexas.edu!not-for-mail From: DCOLEMAN@UPS.EDU Newsgroups: rec.aviation.misc Subject: Ethylene Glycol: ITs use as a Aircraft De/Anti-Icing Fluid Date: 8 Mar 1994 11:43:45 -0600 Organization: UTexas Mail-to-News Gateway Lines: 223 Sender: daemon@cs.utexas.edu Message-ID: <940308093611.64a7@UPS.EDU> NNTP-Posting-Host: cs.utexas.edu NOTE: This short paper was written at 2'oclock in the morning. It has numerous mistakes as is just plain simplifiied. It was written for my General Chem (CHEM 101) class, so it really doesn't matter anyway. Besides the biblography is probably the most interesting thing anyway! Take care and no flames please, this is just something I am doing for your interest! David Coleman March 6, 1994 Chemistry 11 BA Anne Wood Ethylene Glycol :Its Use as a De/Anti-Icing Fluid For Aircraft Ethylene Glycol is the simplest member of the Glycols, which are basically organic compounds belonging to the alcohol family. Ethylene Glycol is one of the most widely used and versitile chemicals today. It is used in a variety of household and industrial settings, from pen ink to explosives to glue. This variety of usage helped make ethylene glycol the 30th highest-volume chemical produced in the U.S. in 1991.1 Ethylene Glycol is very a simple compound. With two hydroxyl (OH) groups attached to separate carbon atoms the formula is C2H6O2, or CH2OHCH2OH. It can be derived in four basic ways; (1) Air oxidation of ethylene followed by hydration of the ethylene oxide formed, (2) Acetoxylation, (3) From carbon monoxide and hydrogen from coal gasification, and (4) Oxirane process.2 Among its properties, ethylene glycol is a clear, colorless, and syrupy liquid, which is odorless and hygroscopic. It is soluable in water, acetone, and alcohol, and can lower the freezing point of water substantially.3 One problem with ethylene glycol is that it is considered a toxic chemical and a spill could cause human health problems and environmental damage. Yet, the benefits of using this chemical is still considered to outweigh its costs, especially as a de/anti-icer for aircraft. One of the many important products which ethylene glycol is used for is as a aircraft deice, or anti-icer. We have seen grusome pictures that the affect of icing can have on aircraft performance. For Example, in the winter of 1981, an Air Florida 737 departing Washington National Airport enroute to Florida plunged into the icy Potomac River, the NTSB cited icing as one of the primary causes. In 1990, a Northwest DC-9 went off the edge of the runway into the Hudson River, struggling to depart La Guardia Airport. One of the causes was found to be wing ice. Wing ice kills aircraft performance. Normally, on a clean wing, the airflow will be laminar, or very close to the wing. This laminar flow keeps the small cushion of air, called the Boundary Layer, which is between the flowing air and the surface of the wing, to a minumum. However, when a obstruction to the laminar flow is present, such as with wing ice, the thickness boundary layer increases dramatically, changing the flow of the wind, and changing the shape of the wing. (It is very similar to the way hair will effect the performance of a swimmer.) This can create a whole new ball game for the pilot, whom expects the aircraft to perform a certain way under a certain set of variables. But with ice, the pilot must be able to fly the aircraft when the varibles become unknown, or are too great to compensate for, sometimes ending in tradgedy. We have known about the effects of ice, and for years, the Federal Aviation Regulations Stated, RNo person may takeoff an aircraft when frost, snow, or ice is adhereing to the wings, control surfaces, or propellers of the aircraft.S Yet tradgedy still occurs. Very Recently, after the Northwest crash occured, the FAA decided to change the regulations on Air Carrier aircraft. Before, aircraft would be deiced at the terminal and sent on there way, often being delayed for 45 minutes to an hour, waiting for departure slots. During this time, enough snow or ice could accumilate, radically altering the aircrafts performance. Now, the new regulations give the pilot a time limit from teminal to runway, in order to make sure that the aircraft is not contaminated. This time limitation is based on the performance of the de-icing fluid, with its prime component being ethylene glycol. There are, two types of ethylene glycol derived solutions currently in widespread use in North America. The first is called Type 1 fluid, which is described mostly as a de-icer, and the second is called Type 2 fluid, which is described mainly as a anti-icer. The differance between Type 1 and Type 2 is primarily viscosity.4 Type 1 is a mixture of ethylene glycol, and water that is warmed to 180F and applied under pressure to clean ice and snow off the wings and stabilizers.5 Enough ethylene glycol is included in the mixture to keep the solution itself from freezing. Type 1 fluid provides about 15 minutes of holdover protection in steady snowfall, and only 3-5 minutes in freezing rain.6 Type 2 fluid is also a ethylene glycol and water mixture but includes a polymer as a thickening agent.7 The fluid, which has the consistency of molasses, is not heated before it is applied. It adheres to the surface rather than running off.8 Treatment of the wing with Type 1 fluid must be done prior to treatment with Type 2 fluid, because type 2 fluid is strickly a anti-icing fluid, and will persist in the presence of ice and snow.9 During the takeoff roll, the shear force caused by the air moving across the wing will blow the fluid off, leaving a clean and smooth surface. After 45 minutes of steady snowfall, however, Type 2 protection can be diluted to the point where the surface becomes contaminated.10 The use of Type 2 fluid only became widespread in the U.S. recently, due to the change in regulations and the lowering cost of its use. Before, its was used mainly at major airports where aircraft would frequently sit in line waiting for a departure slot, and where the special equipment needed for its application could be found. Now, Type 2 is a luxury, even being used on aircraft expected to remain overnight at an airport where freezing precipitation is forecast, making the aircraft easier to clean in the morning.11 The use of both Type 1 and Type 2 fluids comes with its associated costs, both monetarily and environmentally. Since the fluids are applied in highly different fashions, seperate systems must be used for there application which can be very costly, in the beginning. Yet, over time the cost will undoubtedly decline, and the benefits of using both types of fluids at once will accrue. The environmental cost of using these types is twofold; one being the actual costs of regulation, and two being the destructive affects these fluids may have on human health and water supplies. With tighter and tigher regulations, the monetary costs of meeting these regulations will increase, unless alternative solutions to disposal such as chemical recycling are used. Things to consider are the fact that runoff should be expected due to the size and nature of aircraft deicing, yet a relese of 1 lb. or more of ethylene glycol must be reported to the EPA as a toxic spill.12 Even with proper recovery systems at hand such as, holding tanks below the tarmac, the fluid must be treated before leaving the field. One alternative, which is present at the new Denver International Airport, is to have a on site treatment plant which hastens the degradation of Glycols.13 The best alternative however, would be to recycle the used fluids into saleable materials such as polyesters or automotive anti- freezes, but this is still under development. The relese of ethylene glycol into the environment could cause serious damage, to the health of our nations waters. Because ethylene glycol, and other glycols for that matter, are alcohol derivatives, they tend to consume large amounts of aerobic bacteria and absorb oxygen at high rates. This can pose problems to our sewage treatment facilities, but most importantly, large releases could devastate marine life in our waterways.14 If ingested by humans ethylene glycol can cause irreprable kidney damage, or death, if enough is ingested (approximately 100 mL).15 The OSHA requires that ethylene glycol be handed with goggles, gloves and a respirator, and if handled indoors, mechanical exhaust systems would be required.16 Thus it is easy to see that the use of ethylene glycol is a trade-off, between flight safety, and the environment. The use of ethylene glycol as a de/anti-icer for aircraft is probably the most noble of all of its uses. It keeps the flow of aircraft traffic from coming to a halt while providing for a safe passage. Although the costs associated with its use, including monetary and environmental costs can be quite high, its benefits still outweigh the costs. Suitable environmentally safe chemicals which are non-toxic and biodegradable will surely be seen in the future, but today the use of ethylene glycol is standard, and will remain so. End Notes 1Lewis, Richard J. Sr., Hawleys Condensed Chemical Dictionary, 12th Edition, Van Nostrand Reinhold:NY, 1993 p. 487. 2Lewis, Richard p. 487. 3Lewis, Richard p. 487. 4Hughes, David, Aviation Week and Space Technology, v136 p. 29, March 30, 1992. 5Hughes, David, p. 29 6Hughes, David, p. 29 7Hughes, David, p. 29 8Hughes, David, p. 29 9Hughes, David, p. 29 10Hughes, David, p. 29 11Hughes, David, p. 29 12Aviation Week and Space Technology, v138 p. 44, January 11, 1993. 13Aviation Week, p. 44. 14Aviation Week, p. 44. 15Lewis, Richard J. Sr., Hazardous Chemical Desk Referance, 3rd. Edition, Van Nostrand Reinhold:NY, 1993 p. 577. 16Lenga, Robert E. The Sigma Aldrich Library of Chemical Safety Data, 1st. Edition, Sigma Aldrich Corp.:USA, 1988, p. 904. Bibliography Hawleys Condensed Chemical Dictionary, 12th Edition, Richard J. Lewis Sr. p. 487, Van Nostrand Reinhold:NY, 1993. CRC, Handbook of Chemistry and Physics, 72nd Edition, David R. Linde, Editor, CRC Press: USA, 1991. LangeUs Handbook of Chemistry, 19th Edition. John A. Dean, McGraw-Hill:USA, 1992 Hazardous Chemical Desk Referance, 3rd. Edition, Richard J. Lewis Sr., Van Nostrand Reinhold:NY, 1993 p. 577. The Sigma Aldrich Library of Chemical Safety Data, 1st. Editon, Robert E. Lenga, Sigma Aldrich Corp.: USA, 1988 p. 904. REuropean-Developed Anti-icing Fluid Expected to Gain Acceptance in U.S.S Aviation Week and Space Technology, David Hughes, v136, p. 29, March 30, 1992. RRecycling offers Disposal SolutionS Aviation Week and Space Technology v138, p. 29, March 30, 1992. RSearch Underway For Efficent FluidsS Aviation Week and Space Technology v138, p. 29, March 30, 1992. REPA to Address Disposal of Deicing FluidS Aviation Week and Space Technology, v139 p. 32, September 27, 1993. RLarge Aircraft Ground De-icingS Flying Safety v49:8, p. 6, August, 1993. RAerodynamic Effects of Deicing and Anti-icing FluidsS NASA Technology Brief, v18:2 p. 95, February, 1994. RAircraft Deicing....Why the Aircraft Should be Kept CleanS Flying Safety, v49:11 p. 14, November 1993. RAerodynamic Effects of Aircraft Ground Deicing/Anti-icing FluidsS Gill, E.G., Zierten T.A., Journal of Aircraft, v30:1 p. 24, January 1993. end -------------------------------------------------------------------------------- Dave Coleman - DCOLEMAN@UPS.EDU * Cadmus Corporation Commercial/ Multi/ Instrument * Suite 525 N1PC / N150P / N150CP * One Northfield Plaza PZL-150A KOLIBER "Hummingbird" * Northfield IL. 60093 (H) 206-761-1372 * 708-446-2644 (F) 708-446-2749 "The Differance between Driving and Flying: You drive a Car with a yoke, you fly an Airplane with a Stick!" 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