Aircraft Deicing Research Articles

Snow Nowcasting Using a Real-Time Correlation of Radar Reflectivity with Snow Gauge Accumulation

This paper describes and evaluates an algorithm for nowcasting snow water equivalent (SWE) at a point on the surface based on a real-time correlation of equivalent radar reflectivity (Ze) with snow gauge rate (S). It is shown from both theory and previous results that Ze–S relationships vary significantly during a storm and from storm to storm, requiring a real-time correlation of Ze and S. A key element of the algorithm is taking into account snow drift and distance of the radar volume from the snow gauge. The algorithm was applied to a number of New York City snowstorms and was shown to have skill in nowcasting SWE out to at least 1 h when compared with persistence. The algorithm is currently being used in a real-time winter weather nowcasting system, called Weather Support to Deicing Decision Making (WSDDM), to improve decision making regarding the deicing of aircraft and runway clearing. The algorithm can also be used to provide a real-time Z–S relationship for Weather Surveillance Radar-1988 Doppler (WSR-88D) if a well-shielded snow gauge is available to measure real-time SWE rate and appropriate range corrections are made.

Studies of the environmental fate and effect of aircraft deicing fluids: Detection of 5‐methyl‐1H‐benzotriazole in the fathead minnow (Pimephales promelas)

This paper presents the results of a number of field and laboratory studies to evaluate the environmental impact of aircraft deicing and anti-icing fluids (ADAFs) on aquatic systems. Both 5-methyl-1H-benzotriazole (5-MeBt) and 4-methyl-1H-benzotriazole (4-MeBt), known additives to ADAFs, were found in whole-tissue extracts from minnows placed downstream of an effluent outfall that receives ADAF contaminated runoff from General Mitchell International Airport (Milwaukee, WI, USA). Neither of these compounds was detected in tissues from minnows placed upstream from the airport. A toxicity assessment of water collected during the minnow exposure studies utilizing Hyalella azteca, Pimephales promelas, and Ceriodaphnia dubia showed greater toxicity in a secondary airport outfall containing ADAFs when compared to upstream non-ADAF-contaminated samples. In two 28-d static renewal tests using 5-MeBt laboratory-fortified waters, 5-MeBt was detected in whole-tissue extracts of minnows at all concentrations tested. In studies using laboratory water fortified with 5-MeBt, the median lethal concentration (LC50) of 5-MeBt for P. promelas was found to be 22.0 mg/L. The LC50 for C. dubia to 5-MeBt laboratory-fortified water was found to be 81.3 mg/L. The 25% inhibition concentration (IC25) of 5-MeBt for the green alga Selenastrum capricornutum was 23.2 mg/L, and the average median effective concentration (EC50) for Microtox was 4.25 mg/L. The results of these field and lab studies indicate that additives, other than glycols, used in aircraft deicing fluids can be found in aquatic systems and may be of greater risk than previously believed.

Nitrification Inhibition Using Benzotriazoles

ABSTRACT The common corrosion inhibitor, 1H-benzotriazole (Bz), found as a component of glycol-based aircraft deicers, and its derivatives such as 5-chloro-1H-benzotriazole (CBz), 1-hydroxy-benzotriazole (HBz), and 5-methyl-1H-benzotriazole (MBz), are all potential nitrification inhibitors. The inhibitory effect on the nitrification of urea-N fertilizer in agricultural soils was examined over a four-week period. All the compounds tested, except HBz, have the ability to inhibit the nitrification of urea-N fertilizer effectively. Their inhibitory capabilities depend on the structural components of the soil, particularly organic matter (O.M.). In the soil with the largest percent of O.M. (2.3%), inhibition by all the benzotriazole derivatives was considerably decreased. In the soil with least O.M. (0.3%), even HBz, the poorest of the inhibitors, showed signs of inhibition. For Bz, MBz, and CBz, in the range of 90% inhibition was observed in the soil with the lowest O.M. content during a four-week treatment period. On a mass basis, Bz had the greatest inhibitory effect followed by MBz and CBz, whereas HBz showed little inhibition of the nitrification of ureaN in soils with >0.5% O.M. If the inhibitory effects were looked at on a molar concentration basis, there would be little variation in inhibitory potency for MBz, CBz, and Bz. It was concluded that all three are effective nitrification inhibitors with urea-N fertilizer. The incorporation of benzotriazoles as inhibitors could help economize N fertilizers by helping prevent leaching and denitrification. However, the environmental fate of these compounds has not been determined, and they may produce toxicity to plants and other organisms.

Technical Note — The Use of a Very Large Constructed Sub-Surface Flow Wetland to Treat Glycol-Contaminated Stormwater from Aircraft De-Icing Operations

Abstract All of the pollutants found in stormwater runoff at airports, including surface and aircraft de-icing/anti-icing glycols, can be treated and removed to low levels in well-designed sub-surface flow (SSF) constructed wetland systems. There are two common forms of constructed wetlands used for pollution control: those where water flows over the surface among wetland plants (free water surface or marsh type wetlands); and SSF types where the wastewater flows below the normally dry surface of a gravel substrate in which the wetland plants grow. SSF wetlands have no open water to attract waterfowl and are particularly suitable for use at airports. Of the glycol used at Edmonton International Airport (EIA), 80 to 90% eventually entered surface runoff. Edmonton International Airport's operator, the Edmonton Regional Airports Authority (Edmonton Airports) evaluated a number of glycol management options, including constructed wetlands. As a result, a very large SSF wetland system was installed to handle glycol-contaminated stormwater. This paper reviews results of a feasibility study carried out to define design parameters and scale up kinetics for this wetland system, the detailed design that resulted, the SSF wetland's construction, and the start-up of the Edmonton facilities in August of 2000. It also compares the Edmonton wetland system with a similar facility at Heathrow Airport in the United Kingdom.

Anaerobic co-digestion of aircraft deicing fluid and municipal wastewater sludge.

At many airports, aircraft deicing fluid and precipitation mix, becoming aircraft deicing runoff having a 5-day biochemical oxygen demand (BOD5) of 10(2) to 10(6) mg/L. Publicly owned treatment works can be used for aerobic biological treatment; however, it may be more economical to use anaerobic digesters to codigest a mixture of aircraft deicing fluid and sludge. The objectives of this investigation were to determine benefits and appropriate propylene glycol aircraft deicing fluid loadings to anaerobic codigesters. Results demonstrate aircraft deicing fluid can be successfully codigested to produce methane; supernatant BOD5 and Kjeldahl nitrogen concentration were not higher in codigesters compared to a conventional digester. Aircraft deicing fluid loadings as high as 1.6 g chemical oxygen demand (COD)/L x d were sustainable in codigesters, whereas system fed only aircraft deicing fluid with nutrients and alkalinity achieved a loading of 0.65 g COD/L x d. The sludge used increased digester alkalinity and provided nitrogen, iron, nickel, cobalt, and biomass required for methanogenesis. The deicer provides organics for increased methane production.

Best management practices for airport deicing stormwater

With the advent of new regulations concerning aircraft deicing and management of spent aircraft deicing fluids (ADFs), many airports now face the dual challenges of simultaneously maintaining public safety and protecting the environment. This paper provides a theoretical assessment of the potential environmental impact of stormwater runoff and offers detailed current information on alternative deicing fluid application methods and materials, collection and treatment practices.

Fate and toxicity of aircraft deicing fluid additives through anaerobic digestion.

Benzotriazole derivatives are widely used corrosion inhibitors and their fate during wastewater treatment processes is unknown. The purpose of this research was to study the toxic effects and fate of the two commercially significant benzotriazole isomers used in aircraft deicing fluids (4-, and 5-, methylbenzotriazole [MeBT]) during anaerobic digestion. Experiments were executed in microcosms using mesophilic anaerobic biomass co-digesting wastewater sludge and propylene glycol. Sorption of MeBT to digesting solids could be approximated with a Freundlich model, and no anaerobic breakdown of either MeBT isomer was detected. Digesters fed more than 300 mg/L MeBT responded with a significant decrease in methanogenic microbial activity and volatile solids production and a concomitant increase in accumulation of volatile fatty acids. Direct microscopic measurements using fluorescent phylogenetic probes applied to digesting biomass revealed that members of both Archaea and Bacteria domains were sensitive to MeBT. Granular activated carbon (GAC) (volatile solids: GAC = 10%) reduced the apparent toxic effects of MeBT; GAC addition nearly restored the baseline activity of digesters fed MeBT (500 to 1000 mg/L).

High force density eddy current driven actuator

Intense pulsed magnetic fields can be developed by closing a switch and discharging a bank of capacitors through pancake coil. Eddy currents that flow in an adjacent conducting part constrain the magnetic fields to a thin gap, resulting in intense magnetic pressure. A recoilless 7-kg robotic high force actuator is described that can generate a 65-kN force pulse while returning just 600-N recoil force to the robot arm. The resulting gap induction is in excess of 5 Tesla. The system impedance characteristics have been adjusted to take advantage of low voltage. A similar low-voltage system has been proposed for the deicing of aircraft. The pancake coil is held adjacent to the wind leading edge, and the discharge of capacitors through the coil raps the leading edge, dislodging accumulated ice. >

Computational technique for eddy current driven actuator

The magnetic analysis of a new class of eddy-current driven impulse actuators is considered. Driven by capacitor discharge, these actuators generate synchronized force pulses in excess of 100 kN with under 1 kN of recoil force transmitted too the positioner. This technology is being applied to low-payload industrial robots and mechanical impact deicing of aircraft lead edges. These applications are difficult to duplicate experimentally, so there is a demand for computer simulation. The high speed and transient motion of these actuators result in a significant but not constant contribution from velocity-coupled Faraday terms that is not accounted for in conventional finite-element simulation routines. A new computational technique is presented and verified experimentally. >

Keep them out of the deepfreeze with Jefferson Aircraft De-Icing Fluid WD-20

keep them out of the deepfreeze with Jefferson Aircraft De-Icing Fluid WD-20

The adhesion and strength properties of ice

This paper describes a study of the adhesion of ice to various solids. If water is frozen on to a clean metal surface the interface is stonger than the ice and fracture occurs within the ice itself. The detailed behaviour depends on the stresses developed near the interface. If tensile stresses are high the failure is brittle and the breaking stress is temperature independent. If the tensile stresses are below a critical limit the failure is ductile, and the breaking stress increases linearly as the temperature is reduced below 0°C. Ductile failure appears to be determined by the onset of a critical creep rate and the variation of breaking stress with temperature may be explained in this way. This view is supported by the observation that small quantities of dissolved salts which increase the creep rate of ice produce a parallel reduction in the adhesive strength. Surface contaminants on metals reduce the adhesion by a very large factor and it is suggested that this is due primarily to a reduction in the area over which strong metal/ice adhesion occurs. The adhesion of ice to polymeric materials differs from the adhesion to metals. The inter­facial strength appears to be less than the strength of ice and failure occurs truly at the interface. Friction experiments carried out with clean and lubricated metals and polymers sliding on ice provide a measure of the shear strength of the solid/ice interface. The results show a marked parallelism with those obtained in the adhesion experiments; this again emphasizes the close connexion between the friction and adhesion of solids. This study has some bearing on the de-icing of aircraft and of ships sailing in polar seas. The results suggest that ice layers may be removed most readily if brittle fracture can be achieved. Constraint of the ice inhibits brittle fracture and the forces to produce ductile failure are considerably greater. These forces may, however, be reduced by adding small quantities of suitable salts, since these reduce the resistance to ductile flow if the system is above the eutectic temperature. Finally, hydrophobic materials show a very low adhesion; this is particularly marked in the adhesion of ice to polytetrafluoroethylene.