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18 As demonstrated in Chapter 6, the efficacy of control strategies is airport specific. Maximum lead emission reductions realized by providing MOGAS depend on the active fleet and its operations. For example, airports with flight schools tend to have a disproportionately large number of operations from a small number of aircraft which may or may not be approved to use MOGAS. The impact on peak lead concentrations from moving run-up areas is more complex because it depends on the contribution of run-up areas to current peak concentrations and, as found in this study, this can vary widely across airports. Estimates of control strategy efficacy can be refined by collecting on-site activity data and, in this case of moving run-up areas, by con- ducting air quality modeling. The important aspects of the data collection process are described in this chapter. Data collection descriptions with examples are provided in ACRP Web-Only Document 21: Quantifying Aircraft Lead Emissions at Airports. That project used video recordings and still photo graphy when practicable. Activity data can also be collected manually through visual observation. 7.1 Aircraft Fleet Inventory Landing and takeoff operations (LTOs) are a good indicator of overall airport operations and can be used to assess the active fleet. Tail ID numbers are recorded for a representative subset of opera- tions, and these data are processed using the FAA registry (http://registry.faa.gov/aircraftinquiry) to determine the aircraft models and engine types. For the MOGAS option, these data can be matched to lists of MOGAS-suitable aircraft to develop an activity-weighted estimate of the maximum fraction of the fleet that could make the fuel switch. Tail ID numbers of aircraft conducting LTOs can be manually recorded from visual observations, photographed for later review, or videotaped for later playback if the Tail ID numbers are legible. Data should be collected over a range of hours of the day as well as days of the week to ensure a representative sample. For example, flight school operations often follow a training schedule which should be proportionately captured in the data. Each recorded operation by Tail ID number should be time-stamped. While the time stamps are not strictly needed to construct the activity-weighted inventory, they provide insights into fleet operations and can be used to gauge data representative- ness. Furthermore, for air quality modeling, these data can be used to allocate LTOs by hour of the day and, if warranted, by day of the week. In this case it is helpful to also record the runway and whether the operation is a conventional landing, conventional takeoff, touch-and-go (TGO), or taxiback. C H A P T E R 7 Data Collection at Airports
Data Collection at Airports 19 7.2 Activity Data Air quality modeling is most robust when activities are allocated by hour and to their locations at the airport. Video cameras can be used to continuously record aircraft activity by runway; care must be taken to ensure the viewing angles are appropriate to resolve touch-and-go and taxiback operations from conventional takeoffs and landings. Video playback of continuously recorded data can be very time consumingâin this case, a representative subset of hours can be reviewed; alternatively, LTO operations can be visually recorded. One opportunity for efficiency is to combine the LTO data collection with the aircraft fleet inventory (Tail ID) data collection. Tail ID numbers can also be used to filter out jets, which do not use AVGAS and therefore do not contribute to airborne lead concentrations. Regardless of the collection method, it is important these data are time-stamped so they can be processed to generate hourly time-of-day distribu- tion of total aircraft activity, as well as to determine the fraction of total activity resulting from LTOs, TGOs, and taxibacks. Time in Mode data for run-up activities should include the magneto test duration and idling time in the run-up area. These data are best collected by manual recording of visual observations. Data collection must capture a range of conditions (time of day, day of week) and include the time spent by the aircraft in a run-up area (by visual observation), the duration of the magneto test (by audible changes in engine noise during run-up), and the aircraft Tail ID. Some planes bypass the run-up area prior to takeoff, and such instances should be recorded. Time in Mode data should be collected for other activities including taxiing, takeoffs, and landings. These data can be collected by tracking individual aircraft and recording the time and location of each activity. For example, a taxiback would consist of the following data: landing time (time on runway between wheels-down and turning onto taxiway); time taxiing and idling on each taxiway; and takeoff time (time on the runway between starting rollout and wheels-up). The location along the runway for wheels-up and wheels-down should also be recorded; the wheels-up locations will typically be different for TGOs than other types of LTOs. 7.3 AVGAS Lead Concentrations AVGAS samples can be collected from either fixed base operators (FBOs) selling AVGAS at the airport (preferred), or from planes based at the airport. AVGAS lead concentrations can also be collected from the fuel delivery certificates.
