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precipitation conditions for the entire airport by measuring generation of a cost-benefit model; and (4) the design and
precipitation intensity simultaneously at different sites at an conduct of experimental tests.
airport. A significant number of airport and aircraft operators are
Data were collected over two winter seasons, 200708 and still not familiar with this procedure, and training, lack of
200809, at four airports during 15 snowstorms. Data collec- qualified individuals to make assessments, and asymmetrical
tion site separation distances varied from 4,167 ft to 28,500 ft. application are obstacles to its use. The cost-benefit model
Data also were collected during lake-effect snowfall to exam- and presentation aids prepared in this project give operators
ine its effect. tools to assess the benefits of implementing spot deicing for
Measured precipitation rates produced between-site differ- frost removal and consequentially encouraging its use. Guid-
ences in holdover time (HOT) ranging from zero to greater ance material for spot deicing for frost removal based on the
than 50%. It was concluded that differences in HOT in the results of this project will soon be available in SAE ARP 4737.
order of 20 to 30% are of potential operational interest, and The results, findings, and conclusions developed in the
between-site differences greater than 30% are of definite spot deicing study are presented in Chapter 4 of this report.
interest.
The longest separation distances showed a considerably
Increased Use of Aircraft De/Anti-Icing
higher frequency of occurrence of large between-site differ-
Fluid Dilutions
ences in HOT. The differences in HOT generated from dif-
ferent sites begin to impact operations when the sites are sep- In Task 4 of Phase II the use of ADAF dilutions was as-
arated by mid-range distances and have a definite impact at sessed to determine the potential for reductions in the use of
long separation distances. glycol for deicing and anti-icing aircraft.
There is considerable variance in the snow intensity and The objective was to examine current practices and regu-
HOT values derived from test data and from METAR lations related to the use of fluid dilutions and to document
sources. the opportunities, limitations, obstacles and potential bene-
The results, findings, and conclusions developed in the fits associated with their usage. This encompassed (1) a re-
HOT study are presented in Chapter 3 of this report. Appen- view of current government and industry regulations, guid-
dices A through C are available through links on http://apps. ance material, and standards related the use of fluid dilutions;
trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=122. (2) a survey of airlines and deicing service providers; and (3) the
development of a cost-benefit model.
The study concluded that the majority of users do not em-
Increased Use of Spot Deicing
ploy ADAF dilutions, despite the facts that (1) adequate reg-
for Aircraft Frost Removal
ulations and guidelines for their use exist and (2) their use can
In Task 3 of Phase II, an investigation was conducted to be shown to be cost beneficial for many operations. This lack
substantiate the spot deicing for frost removal methodology, of use is likely related to a poor understanding that the finan-
a procedure used to deice small frost-contaminated spots on cial savings to be gained in many cases much outweigh the ad-
aircraft wings in lieu of deicing the entire wings. The objec- ditional costs of introducing dilute fluids into an operation.
tive was to better understand current practices and regulations A cost-benefit model and presentation aids were developed to
for this procedure, quantify its potential benefits, identify po- give operators the tools they need to assess whether imple-
tential obstacles to its use, and provide tools for decision menting the use of ADAF dilutions would be beneficial for
makers to determine whether it is suitable for their operation. their operation.
This effort encompassed (1) a review of current government The results, findings, and conclusions developed in the
and industry regulations, guidance material and standards; study of ADAF dilutions are presented in Chapter 5 of this
(2) a survey of airlines and deicing service providers; (3) the report.
