Counting Aircraft Operations at Non-Towered Airports (2007)

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15 This synthesis report has documented practices that are in use by some state aviation agencies, airports, and metropolitan planning organizations to count and estimate airport opera- tions at non-towered airports. This study revealed that the following methods are being used across the United States and that these methods vary in accuracy: • Count traffic year-round, • Sample traffic and extrapolate annual operations, • Multiply a predetermined number of operations per based aircraft by the total aircraft based at the airport, • Perform regression analysis, and • Ask the airport manager or personnel associated with the airport. The most common method used by the respondents to this study’s survey questionnaire is also the most inaccurate of the methods currently in use; simply asking the airport manager or other related airport personnel what they believe the air- port’s annual aircraft operations are. The Texas Department of Transportation’s 1994 Aircraft Activity Counter Report found that an airport’s operations can be as much as doubled when estimated by the airport manager, as opposed to using the sampling traffic with an acoustical counter and extrapo- lating the sample into an annual estimate. Currently, the most accurate method is to deploy an aircraft traffic counter(s) at an airport year-round, which in theory counts all the traffic at the airport. Seven respondents did this, four of which were airports. It is believed that the next most accurate method to count and estimate operations is to sample traffic with some type of aircraft counter for two weeks in each of the four seasons and to expand that sample into an annual count. One study, when this method was used with the tape recorder acoustical counter, produced results with 9% to 21% margins of error. However, only 6 of the remaining 12 respondents that sampled traffic actually did so for two weeks in each of the four seasons. The other six did not sample in all four seasons, making their results less accurate than those that sampled during all seasons or year-round. Determination of accuracy assumes that the technique used to extrapolate from sample to annual operations is appropriate in characterizing the air- port’s operating environment. There are currently six different methods being used to sample aircraft traffic: • Acoustical, • Airport guest logs, • Fuel sales, • Pneumatic, • Video image detection, and • Visual. The use of airport guest logs and fuel sales, although help- ful, will not track all traffic during the sample period because not all pilots sign into a guest log and not all aircraft purchase fuel with each flight. Additionally, neither of these methods will account for touch-and-go operations. Of the equipment currently being used to sample traffic, the acoustical (includ- ing the sound-level meter and computerized acoustical) and video image detection systems offer acceptable levels of accuracy in detecting aircraft; both are estimated by their manufacturers to be in the 90% range. The acoustical sys- tems are generally less expensive than the video systems, whereas the video systems offer more information, such as aircraft tail numbers. Visual sampling of traffic by a human observer is very accurate, but also very costly and time-consuming. It is believed that the most accurate and cost-effective way to estimate aircraft operations at a non-towered airport is to sample traffic for two weeks for each of the four seasons and extrapolate that sample into an annual estimate. This can be considered most preferable if year-round counts are not feasible, providing that a valid extrapolation is used to expand from seasonal counts to annual operations. As stated previ- ously, the acoustical counter provides a cost-effective, effi- cient, and accurate way to collect the sample, whereas the video image detection system, although more costly, adds additional information that may be useful to the airport. Pneumatic counters and inductance loop counters have seri- ous limitations and would only be useful at airports that have a most simple configuration such as one runway and one entry taxiway, and are not recommended for such activities. Airport guest logs and fuel sales are also not recommended as a way to count traffic. The information received by the states, airports, and metropolitan planning organizations from their aircraft traffic counting programs is being used for a variety of purposes, including justification for airport improvement projects, jus- tification for air traffic control towers, airport environmental documentation, forecasting, economic impact statements, CHAPTER FOUR CONCLUSIONS AND RECOMMENDATIONS

16 performance measures, FAA Airport Master Record Form 5010 reporting, system planning, justification for navigational aids, and airport planning studies. Because the most common method for estimating aircraft operations (asking the airport manager or other airport personnel) may not be accurate, the information being used for these purposes may also be assumed not to be accurate. Additionally, because the meth- ods being used to count and estimate aircraft operations at non-towered airports vary in accuracy, the results are not comparable among the airports. As stated earlier, airport operations data are being used on the FAA Airport Master Record 5010 forms. Each airport has an Airport Master Record that is produced under the guidelines of the FAA Airport Safety Data Program. The information on the Airport Master Record is made available to the general public to use at their discretion. The FAA Order directs the air- port inspector to record the total number of general aviation operations that occur at the airport. It further stipulates that the inspector is to use “FAA tower counts where available. If not available from FAA sources, use estimates based on discus- sion with airport management and/or the fixed base operators.” Coordination of the collection and reporting of accurate airport operations data between state aviation agencies and the FAA is desirable. This can be accomplished by implementing the following: (1) encourage widespread use of appropriate prac- tices identified in this synthesis; (2) when such practices are used, include this information in the Airport Master Record 5010; (3) consider changing the format of the 5010 form to identify the counting practices used.