Counting Aircraft Operations at Non-Towered Airports (2007)

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INTRODUCTION This chapter reviews the type of equipment that was found to be used to count aircraft traffic. It also covers crossover tech- nology and its potential for counting aircraft traffic. Finally, this chapter reviews the specific findings as derived from the responses to the survey questionnaire sent to states and selected airports and MPOs. AIRCRAFT TRAFFIC COUNTING TECHNOLOGY Aircraft traffic counters have developed over time in response to the need for information about activity levels at non-towered airports; however, there are a limited number of manufacturers producing this equipment. The first devices used to count aircraft operations, pneumatic counters, were based on the technology used to count vehicles. The pneu- matic tube counter uses a tube installed across the taxiway surface to record each aircraft as it travels over the tube. On contact with the tube, a pulse of air is triggered that activates a counter to record a movement. These counters cannot distinguish between types of aircraft, between aircraft and vehicles, and do not count touch-and-go operations. The inductance loop counter is another type of counter that transitioned from counting vehicles to counting aircraft. Unlike the portable pneumatic tube, the inductance loop is a wire embedded in the pavement of the runway. Operations are counted as aircraft pass over or fly within a few feet of the surface of the loop. As with pneumatic tubes, inductance loop counters do not distinguish between aircraft and vehi- cles and will not record most touch-and-go operations. Another type of counter developed specifically for use at airports was the tape recorder acoustical counter. A doppler shift triggers the equipment to record the sound of aircraft takeoffs. Landings do not trigger the recording equipment. The tape is audited to determine total takeoffs. For every take- off there is an assumed landing, so the count is doubled to determine total operations for the sampled time. This counter is labor intensive in that it requires the cassette tapes to be audited (listened to) to determine total operations. No known manufacturers were found that still make this equipment. A third type of counter, also acoustical, was developed specifically for aircraft traffic counting. The equipment is deployed within approximately 50 yards of the runway and 8 operates by monitoring acoustic signals and recording only those that match those of an aircraft takeoff. This is a computerized unit similar to the tape recorder acoustical counter. It requires downloading data onto a laptop computer and subsequent review of the data to delete any false counts. The time to perform this function is minimal because it is com- puterized. (This counter will hereafter be referred to as the automated acoustical counter.) This equipment has extremely low power requirements and can be operated with a battery and solar power unit for recharging, allowing it to be left in the field for months at a time. It is rugged and operates in all weather conditions. The software is designed to detect aircraft takeoffs; therefore, the count is doubled to determine total operations for the sampled time. It cannot distinguish between aircraft type, but will detect touch-and-go operations. A video system can be added to this equipment to record images. A fourth type of counter (also acoustical) employed to record aircraft operations uses sound-level meter technology originally designed for environmental noise monitoring. (This counter will hereafter be referred to as the sound-level meter acoustical counter.) As a by-product of measuring noise, this meter is able to differentiate aircraft noise from other noise through software and thereby count aircraft operations. This system uses exist- ing sound-level meters currently on the market and soft- ware designed to detect aircraft takeoffs. It also requires the downloading of the stored data onto a laptop computer and subsequent review to delete any false counts. These systems are rugged, use low power, operate in all weather conditions, and can be left in the field for approximately a month at a time. Another type of aircraft counter in use is a video image detection system that records video of aircraft movement by means of cameras. This equipment was originally developed for security purposes and a spin-off use is for counting aircraft traffic. The camera/recorder is event-driven and is triggered by motion or by a light-to-dark transition in the screen and records the movement to a hard drive. Depending on the sys- tem chosen, the video can then be audited by airport staff or the service provider to identify tail numbers and count traffic. It is labor intensive if airport staff have to review the images and determine operations. This equipment does allow for identification of aircraft tail numbers and subsequent deter- mination of aircraft make and model. As a result, an airport’s critical aircraft and subsequent airport reference code can be determined. If a service provider is used, time involved is minimal, but costs increase. CHAPTER THREE RESEARCH FINDINGS

9POTENTIAL CROSSOVER TECHNOLOGY The magnetometer has been researched as a way to count aircraft operations. Magnetometer technology is currently used at airport security checkpoints to detect metal devices on travelers. Magnetometers are also used in roadway applications to count vehicles passing over the road surface, but was unsuccessful for recording aircraft because of the limited amount of metal in the aircraft and the limitations on the narrow physical area the magnetometer can cover. Taxiways and runways vary in width from 50 ft to 150 ft. The aircraft fuselage and landing gear width can be signif- icantly smaller. Because the aircraft can vary its route over the entire width of the taxiway or runway, the magnetome- ter’s range of detection is too small to reliably detect the aircraft. Radar has been used to count vehicular traffic on roadways. It can detect distant objects and determine their position, as in aircraft radar used for air traffic control. The system works by directing a high-frequency radio wave at the road surface and timing its return signal (13). The ability to count aircraft technically appears feasible; however, the location and range of the sensor in relation to a runway would require extensive testing to determine its potential as an effective counting method. Research on the use of this technology to count aircraft has been conducted by the Iowa Department of Transportation; however, no conclusions have been reached as to its accuracy or cost-efficiency. Aircraft navigational systems currently in place may have the ability to count aircraft traffic. Discussions with a manufacturer of navigational equipment worldwide indi- cated that no known research had been done in this area; however, the use of distance measuring equipment (DME) was a possibility, but it also had some inherent problems that would need to be overcome. DME works on an ultra high frequency, where the aircraft DME equipment transmits an interrogation signal to a ground station that transmits a signal back. The aircraft’s distance is measured based on the time it takes for this signal exchange. Research would be needed to determine how the ground station could count the interrogation signals, uniquely identify them to an aircraft, and determine if it landed. Automatic Dependent Surveillance—Broadcast (ADS-B) is a surveillance concept whereby an airborne or ground vehicle broadcasts its position and the position is received by another application. For example, an aircraft broadcasts its latitude, longitude, altitude, and velocity and other aircraft or systems receive this information for use in a wide variety of applications. ADS-B is an enabling technology for many new applications that are being developed to improve air- borne and airport safety and capacity (14). This technology provides an accurate, low-cost way to gather position infor- mation, and one potential application is counting an airport’s operations. INDUSTRY TRADE ORGANIZATIONS CONTACTED As part of this research project, several aviation organizations were contacted to determine if they had conducted any research on aircraft traffic counting methods. The AAAE, Airports Consultants Council, Helicopter Association Inter- national, National Business Aviation Association (NBAA), and ACI–NA all indicated that they had not performed any such research, nor did they have any information on methods to count aircraft operations at non-towered airports. METHODS USED TO COUNT AND ESTIMATE AIRPORT OPERATIONS One of the primary functions of the questionnaire was to determine the method used by each of the respondents to count and estimate aircraft operations at non-towered airports. The responses are shown in Table 1. The questionnaire results indicated that the most popular method used to count and estimate operations is by simply asking the airport manager, FBO, or other personnel associ- ated with the airport (21 respondents use this method). The next most popular method is to extrapolate a sample count into an annual estimate (19 respondents use this method). The third most popular method is to multiply a predeter- mined number of operations per based aircraft. Of the 13 respondents that use this method, 2 supplied their prede- termined numbers: Louisiana used 500 local and 250 itiner- ant operations per based aircraft and Washington used 250 (low), 350 (medium), and 450 (high) operations per based aircraft, depending on the activity of the airport. Nine re- spondents indicated that they used more than one method to count and estimate operations; therefore, when categorized, some respondents are recorded under multiple methods, which is why the results in Table 1 add up to more than the total number of questionnaires distributed. As stated earlier, 19 respondents take sample counts of operations at non-towered airports. The type of equipment used to take these samples varied. A breakdown of the types of equipment is shown in Table 2. Of these 19 respondents, 3 indicated that they used more than one method, which is why the results add up to more than 19. The most common method used by the survey respondents to sample operations is acoustical counters. Sixteen respon- dents used this method. There are three types of acoustical counters currently being used: the computerized acoustical counter, tape recorder acoustical counter, and sound-level meter acoustical counter. Eight respondents currently use the computerized model, two use the tape recorder model, and six use the sound-level meter model. Of the respondents that take samples by the means identified in Table 2, the lengths of the samples vary. Table 3 summarizes the length of samples taken by each respondent.

10 Seven of the 19 respondents count traffic all year round or during the operational seasons of the airport; therefore, the- oretically, they count all the operations rather than take a sample. Six of the 19 respondents that sample airport traffic take samples in all four seasons and use a seasonal or monthly adjustment factor to extrapolate the sample into an annual count. In addition, two respondents sample in three seasons and four sample in two or fewer seasons. ACCURACY AND EFFICIENCY The survey also included accuracy and efficiency questions related to the aircraft operations counting devices. For those respondents that did not sample traffic, the accuracy was gener- ally unknown. Also, for those respondents that did not sample traffic, time expended was negligible (i.e., the time it took to ask airport personnel what their annual traffic was or to multiply total based aircraft by a set number of operations per based aircraft), except for those that estimated annual airport opera- tions through an airport master plan or system planning process. Generally, the video image detection, sound-level meter, and computerized acoustical counters were reported to be the most accurate systems, usually reporting 80% to 100% accuracy. The most labor-intensive method to count and estimate aircraft operations is through visual observation. The tape Ask Airport Manager, FBO, or Other Personnel Associated with the Airport Multiply a Predetermined Number of OPSBA Take Sample Count Other Do Not Track This Information Multiple Methods (listed elsewhere in this exhibit) Did Not Respond 21 13 19 6 3 9 10 Alabama Arkansas Coloradoa Idaho: non- state-owned airports Kansas Louisianag Maine Minnesota Mississippi Montana Nebraska New Hampshire North Carolina North Dakota Ohio Oklahomaj Pennsylvania: non-DVRPC- counted airports South Dakotak Washington W. Virginia Wisconsin Colorado Florida Georgiab Iowa Kansas Maryland Pennsylvania: non-DVRPC- counted airports Rhode Island South Carolina Tennessee Texas Washington Wisconsin California DVRPC Idaho: state- owned airports Illinois Indiana Maryland Michiganh Nevadad New Mexico New Yorki Oregon Reno Stead Airport Taos Regional Airport Upshur County Regional Airport Utahe Vermont Visalia Airport Watsonville Airport Wyomingl Arizona Colorado New Hampshire New York Utahe Virginia Flagler County Airportc Missouri Nevadad Colorado Kansas Maryland New Hampshire New York Pennsylvaniaf Utah Washington Wisconsin Alaska Connecticut Delaware Denver Regional Council of Governments Hawaii Kentucky Massachusetts Metropolitan Transportation Commission of San Francisco Bay Area New Jersey Southern California Association of Governments Notes: OPSBA = operations per based aircraft; DVRPC = Delaware Valley Regional Planning Commission; FBO = fixed base operator. aColorado estimates from airport managers, using OPSBA to help validate. They also track fuel sales, which they feel b gives them a good gauge of activity. Georgia adjusts the count seasonally by usage type (agricultural operations, flight schools, etc.). cFlagler County Airport has the ability to count traffic with its video detection system, but does not use it for this purpose. dNevada expanded sample counts in the past, but is no longer tracking this information. eUtah uses a statistical model for non-sampled airports. f Pennsylvania uses OPSBA for master and system planning, but asks the airport manager for the FAA Master Record g Form 5010. Louisiana asks the airport manager, who may use OPSBA or guest logs or fuel sales. hMichigan is no longer performing traffic counts owing to budget constraints as of 2007. i New York does not presently conduct a counting program, but did in the past with acoustical counters. For airports not sampled, the airport managers or owners estimated average weekday and weekend day landings during the peak season, and these figures were multiplied by modifiers that considered various factors (including paved versus turf runway). j Oklahoma asks the airport manager. Approximately eight of their airports keep traffic logs. kSouth Dakota asks the airport manager, who may use visual counts and/or airport guest logs to answer the FAA Master Record 5010 Form. l Wyoming does not use equipment to take sample counts. The airport managersí count or guest logs are used. TABLE 1 METHOD USED TO COUNT AND ESTIMATE AIRCRAFT OPERATIONS

11 Computerized Acoustical Counter Tape Recorder Acoustical Counter Sound-Level Meter Acoustical Counter Pneumatic Tube Counter Video Image Detection Visual Airport Guest Logs 8 2 6 2 1 2 1 Idaho: state- managed airports Indiana Nevadad New Mexico Reno Stead Airport Taos Regional Airport Utahe Vermont Oregon New Yorkb California DVRPC Maryland Utahe Visalia Airport Watsonville Airport Illinois Michiganc Upshur County Regional Airport Illinois Wyominga Wyominga Notes: DVRPC = Delaware Valley Regional Planning Commission. aWyoming does not use equipment to take sample counts. The airport managers’ count or guest logs are used. bNew York does not presently conduct a counting program, but did in the past with acoustical counters. cMichigan is no longer performing traffic counts owing to budget constraints as of 2007, but used visual and pneumatic in the past. dNevada expanded sample counts in the past, but is no longer tracking this information. eUtah uses two types of counters and a statistical model for non-sampled airports. TABLE 2 EQUIPMENT USED TO TAKE SAMPLE COUNTS TABLE 3 SAMPLE LENGTHS AND SEASONS Respondent Sample Period and Season Extrapolation Method California 6 weeks; 2 weeks per three seasons (July–October, November–February, March–June) Seasonal or monthly adjustment factor Delaware Valley Regional Planning Commission 8 weeks; 2 weeks per season Seasonal or monthly adjustment factor Idaho: state-managed airports (turf strips) All months that the airports operate (approximately April–October) N/A Illinois One monthly for pneumatic counters; visual counts for five consecutive 12- h days including a weekend; do not sample more than one season Seasonal or monthly adjustment factor Indiana 5 weeks; do not sample more than one season Seasonal or monthly adjustment factor Maryland 8 weeks; 2 weeks per season Seasonal or monthly adjustment factor Michigana 1.5 months; spring and summer Seasonal or monthly adjustment factor Nevadab 2 months; do not sample more than 1 season Seasonal or monthly adjustment factor New Mexico 2–4 weeks per season Seasonal or monthly adjustment factor New Yorkc 2 weeks per season Seasonal or monthly adjustment factor Oregon 6–9 weeks; winter, spring, and summer Seasonal or monthly adjustment factor A/N raey llA tropriA daetS oneR A/N raey llA tropriA lanoigeR soaT Upshur County Regional Airport A/N raey llA Utahd 4 months; one month per season Seasonal or monthly adjustment factor A/N raey llA tnomreV Visalia Airport 4 months; one month per season Seasonal or monthly adjustment factor A/N raey llA tropriA ellivnostaW Wyominge A/N raey llA Notes: N/A = not available. aMichigan is no longer performing traffic counts owing to budget constraints as of 2007, but used visual and pneumatic in the past. bNevada expanded sample counts in the past, but is no longer tracking this information. cNew York does not presently conduct a counting program, but did in the past with acoustical counters. dUtah uses two types of counters and a statistical model for non-sampled airports. eWyoming does not use equipment to take sample counts. The airport managers’ count or guest logs are used.

12 recorder acoustical counter method is also labor-intensive because the tapes must be audited to determine total operations. The video image detection system used by Upshur Country Regional Airport required one-half hour every two to three days to review the images. If a system is chosen that uses a service provider, the images are com- municated by means of the Internet to a central location where they are analyzed, stored, and communicated back to the airport. Accordingly, there is no effort expended by the airport to determine its aircraft operations. The remaining methods to sample traffic typically took less than 2 h per counter deployment. Table 4 summarizes the accuracy and time involved by each respondent who sampled aircraft traffic. The method used to expand the sample count to an annual estimate was most often done with a seasonal or monthly adjustment factor. How the adjustment factor was deter- mined for each respondent was not covered in this study’s questionnaire and is recommended as a subject for further study. Previous research indicated that towered airports were not a valid way to develop adjustment factors for non- towered airports partially because of the availability of more instrument approaches at towered airports, which supposedly made them accessible during inclement weather. This may have been the case more than 20 years ago; however, an increasing number of non-towered airports now have instru- ment approaches. Respondent Accuracy Accuracy Test Approximate Hours Per Count (excluding travel time to airport) reteM leveL-dnuoS ot lauqe ro naht retaerG seY %001–%08 ainrofilaC 2, but less than 4 2 naht sseL seY %001–%08 CPRVD 2 naht sseL seY %001–%08 dnalyraM Utaha 2 naht sseL oN %09–%08 2 naht sseL seY %08–%07 tropriA ailasiV 2 naht sseL seY %08–%07 tropriA ellivnostaW Computerized Acoustical Counter Idaho: state-managed airports (turf strips) 80%–100% Yes Less than 2 2 naht sseL seY %001–%08 anaidnI Nevadab 2 naht sseL seY %001–%08 2 naht sseL seY %001–%08 ocixeM weN 2 naht sseL seY %001–%08 tropriA daetS oneR Taos Regional Airport 80%–100% No Less than 2 Utaha 2 naht sseL oN %09–%08 ot lauqe ro naht retaerG oN %08–%07 tnomreV 2, but less than 4 Tape Recorder Acoustical Counter New Yorkc nwonknU A/N nwonknU 61 oN %06< nogerO Video Image Detection Counter Pneumatic Tube Counter and Visual Michigand (pneumatic tube counter) 60%–70% Yes Less than 2 Illinois (pneumatic tube counter and visual) Unknown N/A Less than 2 for pneumatic; Greater than 60 for visual sgoL tseuG tropriA dna lausiV Wyominge (visual and airport guest logs) Unknown N/A Less than 2 Note: Approximate hours per count includes the answers from Question 10 on the questionnaire, which included person-hours required to perform a traffic count at the airport excluding travel time to the facility. DVRPC = Delaware Valley Regional Planning Commission; N/A = not available. aUtah uses two types of counters and a statistical model for non-sampled airports. bNevada expanded sample counts in the past, but is no longer tracking this information. cNew York does not presently conduct a counting program, but did in the past with acoustical counters. dMichigan is no longer performing traffic counts owing to budget constraints as of 2007, but used visual and pneumatic in the past. eWyoming does not use equipment to take sample counts. The airport managers’ count or guest logs are used. TABLE 4 ACCURACY AND TIME INVOLVED FOR RESPONDENTS THAT SAMPLED TRAFFIC

13 TABLE 5 USES OF OPERATIONS DATA Respondent Ju sti fic at io n fo r A irp or t D ev el op - m en t P ro jec ts Ju sti fic at io n fo r A irp or t C on tro l To w er s En vi ro nm en ta l A ss es sm en t o r Im pa ct D oc um en ta tio n Av ia tio n Fo re ca sts Ec on om ic Im pa ct St at em en ts M ea su re o f Pe rfo rm an ce A irp or t M as te r R ec or d (50 10 Fo rm ) O th er N /A 28 5 8 25 17 11 39 11 3 Alabama √ √ Arizona √ Arkansas √ √ √ √ California √ √ √ √ √ Colorado √ DVRPC √ √ √ √ √ √ √ Flagler County Airporta √ Florida √ √ √ √ Georgia √ Idaho—Statewide Program √ Idaho—30 State-Managed Airports √ √ √ Illinois √ √ √ √ Indiana √ √ Iowa √ √ √ √ Kansas √ Louisiana √ Maine √ Maryland √ √ √ Michiganb √ √ √ Minnesota √ Mississippi √ Missouri √ Montana √ √ Nebraska √ √ √ √ Nevadac √ New Hampshire √ √ √ √ √ New Mexico √ √ √ √ New York d √ North Carolina √ √ √ √ √ √ √ North Dakota √ √ √ √ √ √ Ohio √ Oklahoma √ Oregon √ √ √ √ √ Pennsylvania √ Rhode Island √ √ √ Reno Stead Airport √ √ √ √ South Carolina √ √ √ √ √ South Dakota √ Taos Regional Airport √ √ √ √ Tennessee √ Texas √ Upshur County Regional Airport √ √ √ √ √ Utah √ √ √ √ Vermont √ √ √ √ √ √ Virginia √ √ √ √ Visalia Airport √ √ √ √ √ Washington √ Watsonville Airport √ √ √ √ √ √ West Virginia √ Wisconsin √ Wyoming √ √ √ √ √ Notes: DVRPC = Delaware Valley Regional Planning Commission; N/A = not available. aFlagler County Airport is able to track operations counts with their video image detection system, but they do not use their system for this purpose. bMichigan is no longer performing traffic counts owing to budget constraints. cNevada expanded sample counts in the past, but is no longer tracking this information. dNew York does not presently conduct a counting program, but did in the past.

14 COSTS The cost associated with estimating aircraft operations at non-towered airports varies depending on the method employed. Costs include equipment (capital purchase and installation) and operating (maintenance, data collection, and analysis) costs. This section looks only at equipment costs. If operations estimates are obtained simply by asking airport staff what their operations are, then the cost is negligible and there are no equipment costs. If sample counts are taken, the cost of the equipment varies depending on the approach taken. The sound-level meters and computerized acoustical counting equipment costs range from approximately $4,500 to $5,600 per coun- ter. Owing to the nature of the equipment, one acoustical counter can usually count only one runway. If the runway is exceptionally long, more than one counter may be needed for one runway. Video image detection equipment costs vary depending on the runway configuration. Minimally, approximately $20,000 would be required to count a one-runway airport. If pneumatic counters are used, the equipment costs vary depending on the complexity of the airport layout. One counter is needed for each entry and exit to the runway. If a runway has four exits, then four counters could be needed. The cost of each counter is approximately $400. Visual counts have no associated mechanical equipment, but are the most expensive because this method is labor inten- sive, requiring hours of visual survey. Volunteers could be used to perform this function, but quality control could be an issue. USES OF DATA Respondents were also requested to report on their uses of the aircraft traffic data they collected. The most common use of the data was to include it on the FAA Airport Master Record Form 5010 (39 respondents did this). The next most common use of the data was for justification for airport development projects (28 respondents did this), followed closely by use in aviation forecasts (25 respondents did this). Seventeen respondents use the data in economic impact studies, 11 as a measure of performance (i.e., is the airport being utilized to an acceptable level for its given capacity), and 8 for environmental studies. Additionally, five respon- dents indicated that they had used it to justify air traffic con- trol towers. The uses are detailed in Table 5 by respondent. The other uses for the data, as provided by the respon- dents, are shown in Table 6. esU rehtO tnednopseR Arizona Airport master plans California Airport master plans DVRPC Regional airport system planning Florida System plan Illinois Inventory report Louisiana None New York System plan eligibility; FAA Reliever Designation for Privately Owned Airports North Dakota GPS and AWOS site justification; local–itinerant operations split; percentage of aerial spray operations; percentage of air taxi operations; percentage of military operations Oregon Justification to keep airport open Washington System planning; master planning Watsonville Airport Political: value of airport to city officials to counter anti-airport groups Notes: DVRPC = Delaware Valley Regional Planning Commission; GPS = global positioning system; AWOS = aviation weather observing system. TABLE 6 OTHER USES OF OPERATIONS DATA