Enhanced AEDT Modeling of Aircraft Arrival and Departure Profiles, Volume 1: Guidance (2018)

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  Page 6   radius of about 20 miles up to an altitude of 10,000 ft Above Field Elevation (AFE)). ANP EUROCONTROL’s Aircraft Noise and Performance (ANP) database, the source of the aircraft flight procedures and the underlying flight performance data used to calculate aircraft trajectories. Calibrated Airspeed (CAS) The indicated airspeed of an aircraft (as read from a standard airspeed indicator), corrected for position and instrument error. 2 Available Modeling Methods This section describes the spectrum of profile modeling methods, from simple to complex, including those used in the legacy model INM, functions new to AEDT, and the new ACRP 02- 55 datasets and tools. Figure 1 illustrates these methods, arranged left-to-right from the least complex to the most complex. Complexity was defined according to the needs for data, resources, and modeling expertise to implement each method. The goal of ACRP 02-55 is to “fill in the gaps” by providing a low-complexity set of data and tools for profile customization. Going back to the legacy INM model, there are two traditional methods available to define flight profiles: using a manufacturer-provided default profile, or fully developing from scratch a user-defined profile. The latter method involves extensive coordination with aircraft operators (i.e., airlines) and approval from the FAA Office of Environment and Energy to use non- standard model inputs for Federally-sponsored studies. These methods are indicated in blue in Figure 1. With the release of AEDT, two new methods were introduced; they are highlighted in yellow in Figure 1. The Altitude Controls feature allows the user to define specific altitudes along an approach or departure trajectory, provided that the user has access to such data. The Sensor Paths feature allows for even greater control of the three-dimensional trajectory via the direct input of radar tracking data to the model. However, this method is not typically used for airport- level analysis. ACRP 02-55 has developed the new data and methods indicated in green in Figure 1. The new data consist of alternate default profiles for specific aircraft, developed from radar tracking data from a collection of US airports as part of the ACRP 02-55 research. They include departure profiles based upon flexible speed, reduced thrust, and reduced thrust combined with increased weight. In addition to these new default profiles, a Profile Customization Tool (PCT) has been conceptualized by the ACRP 02-55 team. The PCT exists as “pseudo code” that could be implemented into a stand-alone tool or into AEDT. The focus of ACRP 02-55 is to provide profile modeling data and tools for arrival and departure operations at any size of airport. However, helicopters and military aircraft are not addressed in this project. Touch-and-go operations are also not included.

  Page 7   Figure 1. Profile Modeling Methods in AEDT and ACRP 02-55 Existing AEDT Methods Originating from INM The standard or default flight profiles available in AEDT were originally developed for the INM. The standard profiles are made up of steps that still generally conform to the original version of SAE Aerospace Information Report (AIR) 1845 “Procedure for the Computation of Airplane Noise in the Vicinity of Airports.” There are two different types of standard profiles, procedural standard profiles and fixed-point standard profiles. Procedural standard profiles are defined as a series of procedure steps that the model follows, using aircraft-type specific flight performance parameters to calculate a trajectory. Fixed-point profiles, on the other hand, are a set of fixed points that define a single trajectory and associated thrust levels that do not account for local conditions. When originally created, standard profiles were intended to calculate trajectories for airport noise studies in an era where airport noise was dominated by jet noise relatively close to airport boundaries. At that time, aircraft position information based on radar data was rarely available to airport noise modelers, and available computing power was very limited. The profile customization options currently in AEDT (which are the equivalent of the methods used in INM) include the creation of user-defined procedural or fixed-point profiles and/or the creation of user-defined aircraft performance coefficients. When creating user-defined profiles, modelers typically alter profiles by modifying existing procedure steps, replacing existing procedure steps, or adding new procedure steps. Procedure steps include, for example, takeoff, climb, descend, land, and decelerate. It is uncommon for users to create user-defined fixed- point profiles because of the need to specify thrust values in addition to trajectory data. The creation of user-defined aircraft, with modified flight performance data, can also be used in conjunction with existing standard or new user-defined profiles to alter modeled trajectories. For example, a copy of an existing aircraft can be created with modified thrust coefficients and be assigned to fly a copy of an existing standard procedural profile. The thrust coefficients can be modified in such a way that, for example, they simulate a reduced-thrust takeoff version of the

  Page 8   assigned flight profile. As discussed later in this Guidance Document, FAA approval is required for any user-defined custom profile – a process which can be time and resource intensive. Table 2. AEDT Procedure Step Types and Performance Coefficients Step Type Description Takeoff At ground level, using a given thrust setting and flap setting, accelerate to a CAS that supports climb. Climb Using given thrust and flap settings, climb at constant CAS to a given altitude. Cruise-Climb Using a given flap setting, climb at a given angle to a given altitude and CAS; determine thrust through a force balance. Accelerate Using a given thrust setting and flap setting, accelerate in climb to a given CAS at a given Rate of Climb (ROC). Accel-Percent Using a given thrust setting and flap setting, accelerate in climb to a given CAS with a given acceleration energy share (expressed as a percentage). Descend Descend at a given angle to a given altitude and CAS; compute thrust using a given flap setting, based on a simplified force balance. Descend-Decelerate Descend at a given angle, nominally to a given altitude and CAS; compute thrust using a given flap setting, based on a complete force balance. Descend-Idle Descend at a given angle, nominally to a given altitude and CAS; compute thrust using the idle flap setting. Level Maintain altitude over a given distance, reaching a given CAS; compute thrust using a given flap setting, based on simplified force balance. Level-Decelerate Maintain altitude nominally over a given distance, reaching a given CAS; compute thrust using a given flap setting, based on a complete force balance. Level-Idle Maintain altitude nominally over a given distance, reaching a given CAS; compute thrust using the idle flap setting. Land At ground level, starting from landing CAS (at a given flap setting), reach a given CAS and percentage thrust over a given distance. Decelerate At ground level, starting from the previous step's final CAS, reach a given CAS and percentage thrust over a given distance. Coefficient Description Jet Thrust Coefficients For each rated thrust setting of a jet engine, coefficients to determine corrected net thrust, based on CAS, pressure, and temperature. Propeller Thrust Coefficients For each rated thrust setting of a piston or turboprop engine, coefficients to determine

  Page 9   corrected net thrust, based on TAS and pressure. Flap Coefficients For each flap setting of an airplane, coefficients to determine drag-to-lift ratio, landing CAS, takeoff CAS, and the aerodynamic component of takeoff ground roll length. New Methods Provided with AEDT The AEDT model provides the ability to define an aircraft’s altitude for any points along a ground track with an altitude of greater than 500 feet Above Field Elevation (AFE). This capability was originally used for airspace procedure noise modeling in the FAA’s Noise Integrated Routing System (NIRS) model; with AEDT, it is now available for use in airport noise studies as well. A user provides a set of altitude controls along the ground track. Each control consists of a target altitude and a control code (At, At-or-Above, At-or-Below) that indicates the altitude constraints above and below the target. AEDT then calculates flight paths (for civilian jet, turboprop, and piston aircraft) within the limits of a given aircraft’s performance characteristics based on the altitude controls. One advantage of this method is that, if modelers use AEDT to develop profiles, then FAA-AEE approval is not required. AEDT also provides a “Sensor Path” functionality, allowing users to input a set of 4-dimensional points (latitude, longitude, altitude, and speed) for which AEDT will follow given the flight performance constraints defined in the model. This gives users the ability to explicitly define aircraft altitude and speed profiles, with the current limitations that the flights must be runway-to- runway and input speed values are ignored at altitudes below 10,000 feet AFE. Due to the requirement of runway-to-runway flight trajectory information, sensor paths are not intended for use in single-airport studies and are therefore not discussed in this Guidance Document. New ACRP 02-55 Methods ACRP 02-55 has developed new data and methods to supplement those already available in AEDT. The new data consist of alternate standard profiles for specific aircraft, developed from radar tracking data from a collection of U.S. airports as part of the ACRP 02-55 research. Radar trajectories were processed and analyzed for a selection of representative aircraft classes including heavy jets, larges jets, small jets, large turboprops, small turboprops, large pistons, and small pistons. These aircraft classes were selected to represent a large portion of the fleet mix present at various airports nationwide, from general aviation facilities to large hub airports. From these trajectories, procedural profiles were developed for all commercial aircraft types available in AEDT. In total, 840 new approach and 1,410 new departure procedural profiles were created for this project. The flexibility of the available AEDT procedure step types in matching sample radar altitude trajectories was leveraged to develop three sets of departure profiles as well as one set of arrival profiles. Three sets of departure profiles were developed because the research The intent of the new alternate profiles is to provide AEDT users with more built-in profiles to choose from. However, until these new profiles are formally added into AEDT, a model user would have to follow the FAA custom profile approval process in order to use them.

  Page 10   determined that the use of reduced-thrust settings and potentially increased weight assumptions is helpful in order to obtain reasonable approximations without exceeding speed limits (i.e., the 250 knot constraint). The three sets of alternative default departure profiles are based upon flexible speed, reduced thrust, and reduced thrust combined with increased weight, as described below:  Flexible Speed: Profiles which best match radar altitudes, constrained to full rated thrusts and standard weight, with no constraint to keep CAS below the maximum CAS of the standard profile (usually 250 knots), i.e., the speed is not constrained to the standard limit of 250 knots CAS at altitudes below 10,000 ft Mean Sea Level (MSL).  Reduced Thrust: Profiles which best match radar altitudes, allowing scaled-back rated thrusts, but constrained to use standard weight and keep CAS below the maximum CAS of the standard profile.  Reduced Thrust and Increased Weight: Profiles which best match radar altitudes, allowing scaled-back rated thrusts and increased weight, but constrained to keep CAS below the maximum CAS of the standard profile. The primary characteristic of the new arrival profiles are the common use of level-off procedures at many airports. From the nationwide radar data analyzed during the research project, typical level-off altitudes and distances were determined as averages and included in the alternate profiles. Arrival profiles match radar altitudes, using the standard profile's weight, CAS schedule, and flap schedule. The new alternate default profiles provide increased coverage of frequently used real-world flight profiles. However, it is not possible to generate every possible profile in order to fully cover the entire range of real-world profiles. Therefore, a Profile Customization Tool (PCT) has been conceptualized by the ACRP 02-55 team. The PCT exists as “pseudo code” that could be implemented into a stand-alone tool or into AEDT. Pseudo code is a set of programming instructions that can be used to develop the actual computer code to create a software tool (either within AEDT or as a stand-alone program). However, a completed software tool was not created as a result of this project. Actual implementation of the PCT within AEDT is at the discretion of the FAA. The PCT is a profile editor designed to simply and quickly modify profiles. For example, to customize an arrival profile, the user would enter the level-off altitude and distance spent level for a specific aircraft type. To customize a departure profile, the user would enter the initial altitude of a desired acceleration segment, the desired length of that segment, and the desired rate of climb. The PCT would use AEDT’s performance data to modify the appropriate existing standard profile to generate a new profile with the user’s desired characteristics. When implemented in AEDT, the PCT would give users another option for creating flight profiles that better match their target trajectories. Because of the limited input required it would be possible to use the PCT without access to full sets of trajectory or procedure data. Because it would be built into AEDT, users would presumably be able to create customized flight profiles without having to go through the current process of obtaining FAA approval for the use of user-defined profiles. More information on the PCT is included in the ACRP 02-55 Final Report.