Deicing demystified

Understanding the value of pretakeoff spraying.

Many airports and air carriers use a third-party provider, such as Integrated Deicing Services, shown here deicing an Airbus A320, to perform deicing services. These entities are trained to the requirements of FAR 121.629, which outlines the requirements of an approved deicing program.

Furthermore, the times given in the HOT tables for Type I deicing fluid assume the fluid is heated, and the holdover time at anything below the temperature specified in those tables becomes an educated guess.

Type II fluid is similar to Type I in the sense that it too is heated for deicing applications. It is more viscous and, when used as an anti-icing fluid, is applied unheated to clean aircraft. Due to its viscosity, it generally has a longer holdover time than Type I fluid in most weather conditions.

This thickness aids in lengthening HOT, but it is of extreme importance to pilots that it should only be applied to aircraft with a rotation speed above 100 kts. Type II fluid is designed to adhere to the surfaces of an aircraft until approximately 100 kts, at which time, through aerodynamic sheer forces, it begins to depart the aircraft.

Hence, Type II is often not available at FBOs, since it has less applicability to varied aircraft types than Type I, which can be used on large and small airplanes alike. Type III fluid, which is used even more rarely than Type II, is considered a middle ground between Type I and II deicing fluids.

In fact, it is so rarely available or applied in the US that FAA only dedicates 1 page of its 43-pp HOT table document to Type III fluids. Typically, Type III fluid is more viscous than Type I, but less so than Type II. Type IV is often used as a complement to Type I fluid at FBOs offering both deicing and anti-icing services.

Green in coloration and more viscous than Type I, Type IV is used exclusively as an anti-icing fluid. In general terms, FBOs carrying both Type I or II deicing and Type IV anti-icing fluids, are less frequently encountered than those carrying only Type I.

Yet, when this combination is found, or if the FBO minimally carries 2 wholly different types of fluids-say Type I and IV-chances are that FBO is a veteran in the field of deicing, and thus well-prepared for major winter events.

Air carrier airports

Another indicator of winter weather prowess may be an FBO's deicing contracts with Part 121 air carriers. While operations to and from airports with airline service may be undesirable due to associated congestion-related delays, FBOs at these airports are often the contracted deicing company to these airlines.

In some cases, there may even be a third-party deicing company that provides deicing services for the entire airport. In either case, these contracts can be advantageous to a Part 91 or 135 operators for many reasons.

Due to the clear structure of, and stringent training requirements for, an approved deicing program as outlined in FAR 121.629, FBO personnel tasked with deicing Part 121 air carriers are highly trained in the field of aircraft deicing.

These FAA-approved deicing programs require recurrent training of personnel and must instruct these personnel on the use of HOT tables, aircraft deicing and anti-icing procedures, including inspection and check procedures, communication procedures, aircraft surface contamination and critical area contamination, how contamination adversely affects aircraft performance, types and characteristics of deicing fluids, cold weather preflight inspection procedures and techniques for recognizing contamination on the aircraft.

Without question, these approved deicing programs are thorough. In retrospect, it's interesting to consider that, at many US FBOs, the same personnel fueling or towing aircraft on a hot summer day are also the deicing experts the industry turns to when winter is in full swing.

Another benefit to operators encountering FBOs with airline deicing contracts is the availability and redundancy of deicing equipment. Deicing equipment and trucks, supplied by manufacturers such as FMC, Premier and Trump, represent a major investment by an FBO.

As with any business, demand must exist in sufficient quantity to justify the capital associated with such an investment. While airports without air carriers may have 1 or 2 mobile deicers, at airports with air carrier service the sheer numbers of aircraft operated by the airlines often warrant double-digit numbers of mobile deicers.

This redundancy in equipment at the FBO can be especially helpful during major winter events. However, that knife can cut both ways, and crews and schedulers are wise to call ahead to the FBO.

Because of the nature of the deicing agreements at these locations, some FBOs may be contractually obligated to provide deicing services to a Part 121 carrier first, effectively nullifying the benefits of equipment redundancies.

Let it sleet, let it ice, let it snow

Air carrier airport or not, it is the local and regional weather patterns that tend to predetermine the type of frozen precipitation that may be encountered at any airport. In the mid-Atlantic states, for example, a cold front will often wedge underneath an approaching low-pressure system, itself carrying warm, moist air from the south.

When that precipitation begins to fall, it starts in the form of freezing rain and sleet and subsequently-after the cold front is firmly entrenched-snow. On unprotected surfaces, such as aircraft parked at an airport, a thick, crusty layer of ice is hidden underneath a heavy snow.

By contrast, in areas of extreme cold, such as the Dakotas and the Rockies, the frozen precipitation may only come in the form of light, powdery snow. It is these varying types of frozen contamination-and their significance-that will dictate the amount of fluid used and the time required to deice properly.

Whatever the weather scenario, airports and FBOs alike tend to handle isolated weather events and continuing weather events differently. To awaken one morning to clear skies and a light snowfall on the airplane is an entirely different experience than finding snowfall continuing and increasing in intensity.

In an isolated weather event, airports may allow an FBO to simply deice the aircraft where it sits. Usually, these arcane rules are found buried in an airport's storm water management plan.

Yet procedures may change entirely in a continuing weather event, where the airport may require aircraft to taxi to a specific location, such as a deicing pad adjacent the runway. When the frozen precipitation is still falling, a review of the HOT tables should be part of the immediate pre-departure planning.

Although winter weather can be a stressful event for pilots and groundcrews alike, it is universally agreed that a deicing bill is always cheaper than an accident.

While often unmentioned, deicing can also be a worrisome procedure for passengers, who may not fully understand the significance of frozen contamination on aircraft performance, but are likely aware of its extreme consequences.

With proper planning and a call ahead to understand the FBO's capabilities and the airport's local procedures, any uncertainty regarding deicing operations quickly melts away.

Douglas Wilson started as a lineman at JGG (Williamsburg VA). An active pilot, he now serves as director of line operations and customer service for Galvin Flying Services at BFI (Boeing Field, Seattle WA).


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