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Â Page 41 Â ï§ Analysis Demonstrating Benefit â Grid-point noise analysis in terms of Sound Exposure Level (SEL). Fuel burn, emissions, and emissions dispersion results are not necessary. ï§ Concurrence on Aircraft Performance â Supported by either an aircraft flight manual or statement from an aircraft operator or manufacturer. ï§ Certification of New Parameters â Definition of variables, units, and demonstration of compliance with SAE AIR 1845. ï§ Graphical and Tabular Comparison â Custom altitude, speed, and thrust profiles compared to the AEDT standard profile, and a quantitative comparison (such as an estimate of the least mean square of differences). Table 11. Profile Modeling Types Requiring FAA Approval Custom Profile Type Description All User-defined aircraft profiles (including modifications to standard profiles) developed by methods other than the FAA- accepted methodology built-in to AEDT. Departure Stage Length Profiles which are defined using methods other than: trip length, estimated takeoff weight, and documented procedures based on ICAO/SAE/ECAC standards. Touch-and-Go Operations Adjustments to touch-and-go and circuit profiles using procedure steps not found in the standard profiles. Military Operations Military profiles for aircraft not having any INM/AEDT standard profiles. Helicopter Operations Helicopter profiles that do not follow INM/AEDT-defined profiles and parameters. Sources: FAA, AEE and Airports Coordination Policy for Non-Standard Modeling Procedures and Methodology, 2009; FAA, Order 1050.1F Desk Reference, 2015 5 Interpretation of Results This section of the Guidance Document describes how to evaluate the reasonableness of the profiles selected or developed; the sensitivity of modeled noise, emissions, and fuel burn levels; and, the impacts of the results of a modeling analysis. Of note, the discussion in this section is general and is intended to provide a guideline. For a specific project or analysis, the modeler will have to determine what is most appropriate, and ultimately which profile modeling methodology to use. First, in order to assess reasonableness, the user should review all aspects of the resulting profile that is output by AEDT (i.e., altitude, speed, thrust, and weight). This can be accomplished within AEDT by using the Flight Performance Report function. This function After applying the methods discussed in Section 4, it is important to determine if the resulting profiles output by AEDT are reasonable â as compared to real-world flight trajectory information.
Â Page 42 Â generates a graph of the track distance versus either altitude, speed, thrust, or weight for any selected flight run in the model. The modeler should confirm that the altitude data input to the model matches the flight profile generated by AEDT (especially when using altitude controls due to the leeway that is present for this method). When selecting from AEDT default or ACRP-defined profiles, only a side-by-side comparison is necessary in order to verify that the output profile matches the original input. When developing custom profiles using the PCT, AEDT altitude controls, or user-defined profiles, additional comparisons are recommended. Because the AEDT will compute speed, thrust, and weight in accordance with the user-input altitudes, the user should confirm that these three variables are reasonable to the extent possible/practical: ï§ Speed: Compare to radar data or published procedures to verify that the AEDT- computed speeds are similar to real-world speeds. ï§ Thrust: Compare to operator-provided information, or to the AEDT default profile, to verify that the orders of magnitude and the transitions of thrust along the profile are reasonable. ï§ Weight: Compare to operator-provided information or to the AEDT default profiles to verify order of magnitude. Second, to assess sensitivity, several comparisons were conducted during the research process which can serve as a guideline when reviewing AEDT results. For example, when comparing fuel burn from AEDT default profiles to the new ACRP profiles, the research found that the difference can range from a decrease of 15% to an increase of 25% or more, depending on the profile and aircraft type. Therefore, both fuel burn and emissions results have the potential to be significantly changed by custom profile modeling. If possible, AEDT fuel burn output should be compared to other sources for correctness such as Flight Data Recorder (FDR) or airline fuel burn data and/or emissions monitoring data. Furthermore, the research found that noise levels can also vary, especially when the actual profile is lower in altitude than the default AEDT profile (for example, for arrivals with level-off segments). Differences in noise vary by location along the flight track and increase as the modeled altitudes deviate from the AEDT default profile. The difference in maximum sound level (i.e., Lmax) at a specific point can range from 0 to 10 dB or more. Therefore, the user should assess the locations on the ground where profiles deviate from the AEDT defaults to determine where the differences in noise may be greatest. If possible, AEDT noise output should be compared to other sources for correctness such as airport noise monitoring system or other measurement data. Finally, based on the discussion above, the modeler should determine if the customized profiles have a significant impact on the overall AEDT results. In particular, when seeking FAA approval for user-defined profiles or non-default profiles, consideration should be given to the level of effort involved in gaining approval versus the sensitivity of modeling results. In some cases, relying on FAA-approved methods such as altitude controls can save time and effort by avoiding the custom profile approval process. In other cases, FAA approval may be necessary to fully customize a profile in order to best capture environmental impacts within the study area. These decisions should be weighed against the resources available and the impacts to scope, budget, and schedule for the analysis.