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1 S U M M A R Y Introduction The objective of this research was to identify, test, and evaluate methods for obtaining aircraft operations counts at non-towered airports. Based on the requests of the ACRP panel for this project, findings from ACRP Synthesis 4 on this same topic, a literature review, a con- tacting initiative, and the budget allocated, three methods of estimating annual operations and four counting technologies were advanced for testing. The methods to estimate annual operations included (1) multiplying based aircraft by an estimated number of operations per based aircraft (OPBA), (2) applying a ratio of FAA instrument flight plans to total operations (IFPTO), and (3) expanding a sample count into an annual estimate through extrapolation. In order to expand a sample into an annual count through extrapolation, the sample first has to be taken. This is typically done by some type of technology designed to count aircraft. The different aircraft counting technologies (used to obtain the sample count) that were advanced to the evaluation stage to determine their ability to count aircraft traffic included acoustic (both automated acoustical and sound-level meter acoustical), security/trail cameras, and video image detection with a transponder receiver. The airports where the estimating methods were tested included multiple non-hub airports with FAA visual flight rules (VFR) towers with less than approximately 730 air carrier operations per year (defined in this study as the small, towered airport datasetâSTAD). Since valid operations data does not exist for non-towered airports, these small, towered air- ports were used as a proxy for the comparison. The airports where the counting technologies (i.e., equipment) were tested included a multiple case study performed at Purdue University Airport (LAF), Indianapolis Executive Airport (TYQ), Paoli Municipal Airport (I42), and Eagle Creek Airpark (EYE). Conclusion on Methods to Estimate Annual Operations Overall, the research team concludes that, based on the study objectives and data, there were no practical and consistent OPBAs found or modeled at small, towered airports nationally or by climate region, even when considering the number of flight schools based at the airport. Therefore, the research team cannot recommend an OPBA or OPBA equation (based on the variables used in this study) for estimating annual operations at non-towered airports. Additionally, based on the data and study objectives, the research team concluded that there were no practical and consistent IFPTOs found at small, towered airports nationally or by climate region. Therefore the research team cannot recommend an IFPTO for estimating annual operations at non-towered airports. Accordingly, to estimate an airportâs operations, the team recommends taking a sample of actual operations and extrapolating annual opera- tions from the sample. Evaluating Methods for Counting Aircraft Operations at Non-Towered Airports
2When taking a sample count, the research team studied four sampling scenarios and recommends sampling for two weeks in each season. This sample can be extrapolated by either a statistical extrapolation process or by use of seasonal/monthly adjustment factors developed from small, towered airports (i.e., STAD). The latter process assumes that the monthly and seasonal variations in traffic at small, towered airports are representative of non-towered airports. Statistical extrapolation uses sample data from the specific airport being studied. Based on this fact alone, the research team recommends using the statistical extrapolation process. This also removes the need for additional data and the influences of outside forces on the extrapolation process. The statistical extrapolation method may appear more mathematically difficult than the monthly/seasonal extrapolation method. However, step-by-step instructions, examples, and forms are available in FAA-APO-85-7, Statistical Sampling of Aircraft Operations at Non- Towered Airports, which make it fairly straightforward. Additionally, Appendix B includes an example of how this is done. Conclusion on Aircraft Traffic Counting Technologies Automated acoustical counters (AAC) are best used at airports with single runways with runway safety areas of 500 feet or less that do not experience significant traffic by exception- ally quiet aircraft. They record takeoffs only. No aircraft information is provided. Accuracy rates of 90% or higher (up to 250 feet from runway centerline) can be achieved if the equip- ment is located properly and sufficiently tested. (Note: The FAA required submission of FAA Form 7460 for each unit placed and units had to be outside of the runway safety area.) The aircraft lift-off point should generally be within approximately 700 feet of a point perpendicular of the counter to be consistently counted. (See Figure S-1.) Multiple counters are required for runways approaching 3,000 feet or moreâthis makes this option more labor intensive on longer runways. Approximate purchase cost at the time of the study was $4,800 each. Exceptionally quiet aircraft are often missed more often than counted (e.g., Cessna 172 with Continental O-300 SER engine was missed at a distance of approximately 50 feet of the unit). These are typically small single engine piston aircraft. Jets, turbo props, and multi- engine piston aircraft are typically louder and are not missed as often. Helicopters are harder to count because they do not have a uniform landing path; to be counted they have to fly over the general area of the counter to be detected. Airports with multiple runways will be difficult to count with consistent, acceptable accuracy. Sound-level meter acoustical counters (SMAC) are best used at airports with single runways and runway safety areas of 150 feet or less. They record takeoffs only. No aircraft Prepared by: Woolpert, Inc. Aircraft lift-off (rotation point) should be within approximately 700 feet of a point perpendicular of the counter, which may 700 feet require multiple counters. AAC 700 feet Counter can be as far as 250 feet from runway centerline. Figure S-1. Placement of AAC at airport runway.
3 information is provided. Accuracy levels of 90% accuracy or higher can be achieved if the equipment is located properly, sufficiently tested, and generally not more than 75 feet from runway centerline. (Note: FAA required submission of FAA Form 7460 for each unit placed and units had to be outside of the runway safety area.) The aircraft lift-off (rotation point) should generally be within approximately 700 feet of a point perpendicular of the counter to be consistently counted. (See Figure S-2.) Multiple counters are required for runways approaching 3,000 feet or greaterâthis makes this option more labor intensive on longer runways. (Approximate purchase cost at the time of the study was also $4,800 each.) Exceptionally quiet aircraft are often missed at distances greater than approximately 50 feet of the runway centerline. (e.g., Cessna 172 with Continental O-300 SER engine). These are typically small single engine piston aircraft. Jets, turbo props, and multi-engine piston aircraft are typically louder and are not missed as often. Helicopters are harder to count because they do not have a uniform landing pathâto be counted they have to fly over the general area of the counter to be detected. Airports with multiple runways will be difficult to count with consistent, acceptable accuracy. Security/Trail Camera (S/TC) are best used at airports with a centralized terminal and hangar area with limited access points and little to no touch-and-go activity. A camera is needed at each access point to the runway. (Approximate purchase cost at the time of the study was $1,000 each.) Accuracy levels approaching 100% can be achieved for recording aircraft entering or exiting the runway environment; however, the units are not able to count touch-and-goes. Exceptionally slow moving aircraft may be missed. Counting aircraft this way is labor intensive because it requires manual tallying of the images. Information on air- craft type, make, and model can be obtained from the aircraft registration numbers by use of the FAA aircraft database. The units are a low-cost option for airports with very simple airfield configurations. (Note: FAA required submission of FAA Form 7460 for each unit placed and units had to be outside of the taxiway safety area.) Video Image Detection (VID) and Automatic Dependent Surveillance-Broadcast (ADS-B) transponder receiver technology is best used at airports with centralized terminal and hangar areas with limited access points and little to no touch-and-go activity. Accuracy levels as high as 90% can be achieved for recording aircraft entering or exiting the runway environment; however, the ADS-B transponder receiver adds little to no value, considering the low equi- page rate of the U.S. general aviation fleet with ADS-B out. (Note: General aviation includes all segments of flying except for airlines and military.) Additionally, the VID does not count touch-and-goes. This is the most expensive option for counting aircraft operations, but also the least labor intensive. (Approximate lease cost at the time of the study was $36,000 for Figure S-2. Placement of SMAC at airport runway. Prepared by: Woolpert, Inc. Aircraft lift-off (rotation point) should be within approximately 700 feet of a point perpendicular of the counter, which may require multiple counters. 700 feet SMAC 700 feet Counter can be as far as 75 feet from runway centerline.
4two cameras and one receiver.) An annual service contract is required. (Note: FAA required submission of FAA Form 7460 for each unit placed and units had to be outside of the taxiway safety area.) Summary Sample counts can be costly and time consuming. The accuracy needed and the cost of the counts should be considered, along with the potential implications of the uses of the resulting annual operations estimates, to determine the appropriate sampling method for an individual airport. The preferred method selected by an individual airport may depend on the individual airportâs situation.
