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46 Key Insights The collection and verification of obstruction data are critical elements of flight safety because they underlie the development of instrument flight procedures and updates to navigational data. Obstruction data collection methods and resources vary broadly based on the type and amount of data that need to be collected. These data range from visual observation to a comprehensive gathering of airport obstruction and planimetric data conducted in accordance with FAA AC 150/5300-18B: General Guidance and Specifications for Submission of Aeronautical Surveys to NGS: Field Data Collection and Geographic Information System (GIS) Standards. The FAA maintains a number of obstruction data resources and tools for basic airport obstruction evaluation tasks. Key Definitions AIRNAV: A software application used by the FAA to manage data in the Aviation System Standards information system. Clinometer or inclinometer: An instrument for measuring angles of slope (or tilt), elevation, or depression of an object with respect to gravity. Instrument approach procedure (IAP): A series of predetermined maneuvers for the orderly transition of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or a point from which a landing may be visually made. Instrument flight procedure (IFP): A published procedure used by aircraft to operate safely to and from airports under instrument flight rules. Instrument flight procedures include depar- ture, arrival, and approach. Instrument flight rules (IFR): A set of regulations and procedures permitting qualified and current instrument flight rules pilots to penetrate clouds and low-visibility conditions. Aircraft must be equipped with radio and navigation instruments and operate under air traffic control flight plans and clearances. Flights are monitored, and traffic is separated by air traffic control. National Airspace System (NAS): The airspace, navigation facilities, and airports of the United States along with their associated information, services, rules, regulations, policies, pro- cedures, personnel, and equipment. Next Generation Air Transportation System (NextGen): A federal program to transform the national airspace system from a ground-based system to a satellite-based system. C H A P T E R 4 Obstruction Data Collection and Resources
Obstruction Data Collection and Resources 47 Obstruction Evaluation/Airport Airspace Analysis (OE/AAA): FAAâs electronic resource for submission and tracking of notices required under FAR Part 77.17 by the public and the FAA internal review coordination of the notices. Visual flight rules (VFRs): A defined set of FAA regulations covering the operation of aircraft, primarily by visual reference to the horizon (for aircraft control) and see-and-avoid procedures (for traffic separation). Visual flight rule weather minimums for controlled airspace require at least a 1,000-foot ceiling and 3 miles of visibility, except for âspecial visual flight ruleâ clearances to operate âclear of clouds.â 4.1 Sources and Uses of Airport Obstruction Data Accurate data are vital to the NAS in the transition to NextGen for air traffic control. The FAA depends on accurate data for the development and maintenance of IAPs. For individ- ual airports, accurate data are most relevant in the development of IAPs. With the transition to NextGen, a highly data-driven system, the need for new and accurate obstruction data is further increased. Ultimately, the FAA desires every airport in the NAS to have interconnected and standardized data. Additionally, the navigational equipment used by pilots to aid in IFR and VFR navigation is dependent on up-to-date obstruction data. Aircraft GPS equipment has advanced to a degree where even handheld VFR GPS equipment can include obstacle informa- tion. GPS equipment manufacturers, which develop and provide the database updates, may use multiple sources for their database updates, but these sources obtain information from the FAA. In turn, the FAA relies on data submission from multiple sources to populate the data- base utilized for procedure development and obstruction data maintenance, such as Airports GIS, FAA flight checks (FAA Form 8240-16), and updates to FAA Form 5010: Airport Master Record. Airports play a valuable role in providing these data to the agency and promoting the safety and efficiency of the NAS. Airport Survey To ensure survey data accuracy, a trio of FAA ACs detail standards for collecting and submit- ting data about airports. Standardizing these processes and the resultant data increases accuracy and efficiency for airports across the nation. The three ACs are the following: â¢ FAA AC 150/5300-16A: General Guidance and Specifications for Aeronautical Surveys: Establishment of Geodetic Control and Submission to the National Geodetic Survey â¢ FAA AC 150/5300-17C: Standards for Using Remote Sensing Technologies in Airport Surveys (Consolidated to Include Change 1) â¢ FAA AC 150/5300-18B: General Guidance and Specifications for Submission of Aeronau- tical Surveys to NGS: Field Data Collection and Geographic Information System (GIS) Standards These documentsâcolloquially shortened to â16, 17, and 18ââwere written for engineering and surveying audiences and generally provide more detail than needed for an airport sponsor or manager. Broad descriptions and highlights of each circular are provided below to assist during the scoping and oversight of airport survey projects. It is important to keep in mind the airportâs current and future needs and scope project tasks accordingly. A successful aeronautical survey project and subsequent obstruction identification require proper scoping and communication. There are a number of interested parties involved in air- port surveysâthe FAA, state agency, airport sponsor, the National Geodetic Survey (NGS), and consultantsâso clear and complete communication is critical. The key points described for each
48 Best Practices for Airport Obstruction Management Guidebook of these ACs should be considered during project development and serve as a reminder to key parties of the required tasks and deliverables. FAA AC 150/5300-16A: General Guidance and Specifications for Aeronautical Surveys: Establishment of Geodetic Control and Submission to the National Geodetic Survey FAA AC 150/5300-16A reviews requirements for geodetic control for aeronautical surveys. Geodetic control points are identifiable physical objects (called marks or monuments) that can be used to tie local survey data into the national system. Once geodetic control has been established, local survey data can be connected to the National Spatial Reference System to ensure accuracy between the local airport survey data and the NAS. The NGS is a clearinghouse of survey marks across the nation. There are two types of geodetic control points: permanent and temporary. Primary airport control stations (PACSs) and secondary airport control stations (SACSs) are used for airports that require permanent geodetic control. FAA AC 150/5300-16A details the requirements for creating and using permanent geodetic control, such as creating a con- crete survey mark, a file format for the collected data, and instructions for GPS antennas. The FAA prefers that all National Plan of Integrated Airport Systems airports have at least a PACS installed, and many airports already have monuments suitable for PACSs and SACSs. Tempo- rary control, a less costly alternative to PACSs and SACSs, uses temporary marks. Figure 4.1 shows a typical monument for a PACS or a SACS. A project survey plan must be submitted to the NGS for approval prior to setting marks. This plan is a substantial, mandatory work item that outlines the type of control to be utilized and the final deliverables to be sent to the NGS. Choosing which type of geodetic control used is an important step in every aeronautical survey project. Airport sponsors should be aware that thorough documentation and reporting are required for aeronautical survey projects. Surveying consultants should be expected to produce a qual- ity control plan, a project survey plan, and a final project report. Regular project status reports may also be desirable. Interviews with pertinent airport personnel are required to complete the work, according to FAA requirements. Airport management should always be interviewed, at a minimum to gain permission for airside surveying. Airport engineers, air traffic control, and other personnel must be interviewed on a per-project basis. Properly planning project work and communication between airport management and field crews is critical to successful project Figure 4.1. Typical monument for a PACS or a SACS.
Obstruction Data Collection and Resources 49 implementation. The AC includes an example airport manager interview that provides a check- list of pertinent items. FAA AC 150/5300-17C: Standards for Using Remote Sensing Technologies in Airport Surveys (Consolidated to Include Change 1) FAA AC 150/5300-17C is a fairly technical document, getting into the nuts and bolts of remote sensing technologies and their use. In broad terms, remote sensing is obtaining data from a distance. An aircraft taking a picture of the ground beneath it is an example of remote sensing. There are two remote sensing technologies approved for airport survey data col- lection: aerial imagery and light detection and ranging (LiDAR). Neither method is perfect; each has its limitations. Satellite imagery is an emerging technology and not yet permitted for airport surveys. Aerial imagery is the most common remote sensing technology for FAA airport projects. An aircraft outfitted with a camera follows a series of flight lines over the projectâs boundary and takes photographs. LiDAR uses laser pulses to collect data and is deployed using aircraft, ground vehicles, or stationary stands. It is best to acquire imagery within 6 months of its intended use. Leaf-on conditions (when trees and shrubs have full foliage) are required for an airport airspace analysis. If a project does not contain an airport airspace analysis element (such as an engineering design project), leaf-off conditions may be acceptable. If ground elevation contours need to be captured in a wooded area, two surveys (one during leaf-on and one during leaf-off conditions) may be needed. A remote sensing plan must be submitted to the FAA for all remote sensing projects. This plan outlines the entire proposed data acquisition. Key items include the following: â¢ General project information (airport name, contact information, etc.) â¢ Project boundary (physical areas and/or obstruction identification surfaces to be covered) â¢ Project parameters (such as flight lines and flying height) â¢ Equipment â¢ Control points â¢ Project schedule â¢ Quality assurance and quality control All remote sensing projects must submit: â¢ Remote sensing and survey and quality control plan â¢ Control points information â¢ Notification of unusual circumstances â¢ Final project report Additional items are also required, depending on whether aerial imagery or LiDAR is used. Imagery must be submitted for evaluation, and, when it is accepted, the FAA will provide an imagery usability report. FAA AC 150/5300-18B: General Guidance and Specifications for Submission of Aeronautical Surveys to NGS: Field Data Collection and Geographic Information System (GIS) Standards FAA AC 150/5300-18B outlines the standards for data collection, classification, and reporting at airports. The combined use of aerial and field data acquisition is discussed. The best method of collection must be determined for each project based on accuracy requirements. Although the technology is rapidly changing, remote sensing is unable to obtain data at the level required for some airport features.
50 Best Practices for Airport Obstruction Management Guidebook The FAA requires independent verification and validation of airport safety data by the NGS or a designated representative. Field surveys are able to capture data more accurately than remote sensing; therefore, some airport featuresâspecifically, runway data and NAVAIDsârequire field survey accuracies. Sponsors will often initiate an airspace analysis survey to identify and analyze objects on and around their airport. These data are crucial for engineering, planning, and flight procedure development. Surveying for an airport airspace analysis has specific requirements. As listed in the AC, points along runways, runway vertical profiles, positions and elevations of NAVAIDs, positions and elevations of obstructions, analysis of obstructing areas and positions, and eleva- tions of certain nonobstructing obstacles are all required. FAA AC 150/5300-18B, Table 2-1: Survey Requirements Matrix (see Table 4.1) lists the requirements for different types of projects, such as instrument procedure development and pavement design. Refer to this table often during project scoping to ensure that the required tasks are completed. Imagery is not required for every project. Typically, image acquisition will be in conjunction with safety-critical data projects involving new or modified instrument procedures, obstruction surveys, ALP updates, etc. Data are considered âsafety criticalâ when they are necessary for safe approach, landing, take- off, and departure flight operations. Safety-critical data have more stringent review and submis- sion requirements. If an upcoming project is going to touch any of the following safety-critical items, then a submittal of the revised data to Airports GIS must be included as well: â¢ NAVAIDs â¢ Obstacles â¢ Runway end â¢ Touchdown liftoff area â¢ Airport control points (specifically airport elevation, touchdown zone elevation, displaced threshold, stopway end) â¢ Runway â¢ Stopway â¢ Taxiway â¢ Visual aids The topics reviewed in these ACs, especially technologies such as LiDAR and satellite imagery and the FAAâs Airports GIS system, are constantly evolving. It is critical to stay current on revisions for these documents and abide by their specifications. An airport survey conducted to the standards in FAA AC 150/5300-16, 17, and 18 provides data for an airport with verifiable accuracy to be submitted to the FAA. Most often, these data are gathered as part of a planning or construction project, as listed in FAA AC 150/5300-18B. The extent of the data collection is based on the projectâs requirements. The results of an airport survey are provided to the FAA through an upload of the data to Airports GIS. There may also be times when an airport sponsor needs only limited survey data, such as when verifying potential obstructions. The data gathering standards prescribed in these ACs must still be followed to obtain the necessary accuracy, but the scope of the work is more limited and all the preapproval steps, such as the survey scope of work, may be limited. Lim- ited survey data can still be uploaded to Airports GIS, but may need to be added as âas-builtâ information. If an airport is uploading survey data that identify a new obstruction, the airport should address the obstruction or develop an action plan prior to uploading the information. This allows the airport to demonstrate the issue and the resolution simultaneously.
1Only when runway construction is involved. 2All 14 CFR Part 139 airports require 10 foot stations. At all other airports the distance between stations is between 10 and 50 feet to meet local requirements. 3Only required for the identified Category II and III special topographic survey. 4For Cat II and III radar altimeter area or if specifically requested. Source: FAA AC 150/5300-18B, Table 2-1. Table 4.1. Survey requirement matrix.
52 Best Practices for Airport Obstruction Management Guidebook FAA DOF and Daily Digital Obstacle File (DDOF) The FAAâs DOF and the DDOF contain all known obstacles (objects penetrating FAR Part 77 surfaces) of interest to aviation users in the United States. The files also include limited coverage of the Pacific, the Caribbean, Canada, Mexico, and the Bahamas. The obstacles are assigned unique numerical identifiers and accuracy codes. They are listed in ascending latitude within each state or county. The DOF is updated every 56 days and serves as the basis for other navigation product updates, whereas the DDOF is updated daily and includes DOF data as well as any data that have been uploaded through Airports GIS the previous day. The obstacles may be verified or unverified. An obstacleâs verified status is indicated by an âOâ in the verification status field. To be verified, the data have been reviewed by the FAAâs Aeronautical Information Services or Obstacle Data Team or have been taken from airport survey data. Verified objects also have an assigned accuracy code. An unverified obstacle is indicated by a âU.â Users must be cautious when using unverified data. For verified obstacles, the DOF includes an associated level of survey accuracy, which denotes how precise the obstacle location is and what degree of error the FAA applies during its analysis and procedure develop- ment in the obstacleâs vicinity. The FAA publishes a daily change file to indicate changes to the DOF. This process allows information uploaded via Airports GIS to be added to the DDOF. Additional information on the DDOF and its formatting is available in the DDOF README file. Obstruction Data Sourced from OE/AAA Data related to existing or potential airspace obstructions can also be sourced from the OE/AAA database itself. The OE/AAA system allows the user to search for a broad range of obstruction cases in various stages of the OE/AAA process: â¢ Proposed cases â¢ Interim cases â¢ Circularized cases â¢ Determined cases â¢ Supplemental notices (indicating that the structure was constructed) For airports establishing an airport obstruction management program or for airport man- agers looking to familiarize themselves with the effect that surrounding airport environs have on their facilityâs airspace, OE/AAA data provide a useful resource. In fact, creating a profile in the OE/AAA system and establishing a subscription for the system to notify a user of any proposed construction within a specific radius of a public-use facility is an effective way of stay- ing informed about any potential proposals that may not have been discovered by the airport through the regular communication channels. As mentioned in the discussion of the OE/AAA process in Chapter 2, after the FAA issues its final determination and the structure is constructed, the proponent is requested to sub- mit supplemental notice Form 7460-2. That information serves as one of the key sources of obstruction data for the FAA. Data Contained in the Airport Master Record (FAA Form 5010) The FAA Office of Airport Safety and Standards is responsible for the collection and maintenance of data on existing public-use landing areas. The office manages the imple- mentation of a program that sources the data from updates to FAA Form 5010: Airport
Obstruction Data Collection and Resources 53 Master Record. The obstruction data collected for Form 5010 updates include information on impacts to airport FAR Part 77 surfaces. The data collection for Form 5010 inspections is conducted by â¢ The FAA during an airport certification inspection (for Part 139 airports) â¢ State transportation or aeronautics agencies as a part of periodic airport inspections â¢ Private contractors performing airport data collection on behalf of the FAA â¢ Airport staff as a part of a periodic update or due to substantial changes to the facility The process of data collection for Form 5010 updates has two inherent benefits for airport obstruction management. The information collected through any of the methods is reflected on the updated Airport Master Record and includes close-in obstacle data for most critical or controlling obstacles affecting FAR Part 77 surfaces. Additionally, the process of data collec- tion by state or private contractors is beneficial for airports that have few or no resources to conduct the basic obstruction analysis. The collection method for Form 5010 data will vary with the inspecting entity. Because the form update does not require survey-grade accuracy to identify controlling obstacles, the degree of data accuracy will vary based on the quality of the tools utilized during the inspec- tion. In most cases, the tools used include basic handheld devices that measure angles and distances to objects. Therefore, the best use of the collected 5010 data is as an indicator of where further study with more accurate survey tools may be needed or to establish a control- ling obstacle for a runway after an airportâs changes. For airports lacking survey capabilities and technical resources, participating in the annual Form 5010 data collection or inspection effort is beneficial for understanding FAR Part 77 surfaces and monitoring changes to airport airspace impacts. Air Carriers While the data gathered by air carriers and charter operators are limited to pilot reports of close-in obstacles, airports and their sponsors should be well informed about the sources of data available to air carriers, as well as the use of the data by FAR Parts 121 and 135 operators serving their airport. Being well informed about sources and use of data can help airports make informed decisions regarding obstruction management and the potential impacts of airport actions on the ability of the operators to serve the community. Generally, data are used by the operators to â¢ Conduct performance analysis and determine maximum useful loads for each aircraft in the fleet at an airport â¢ Evaluate the safety of flight and obstacle avoidance for regular and irregular operations â¢ Evaluate the operatorâs ability to maintain compliance with internal SOPs Impacts on any of the listed factors may result in negative operational and fiscal repercussions for air carriers and surrounding community. In the course of performing any of the obstruction evaluations for operational performance, air carriers rely on a variety of sources and tools to perform their analyses. These include the following: â¢ OE/AAA proposed and completed obstruction evaluation cases â¢ FAA Aviation System Standards integrated services â¢ Specialized IFP design and evaluation software â¢ Specialized aircraft performance evaluation and planning software provided by aircraft manufacturers â¢ DOF and DDOF obstacle data
54 Best Practices for Airport Obstruction Management Guidebook For air carriers, comprehensive and up-to-date obstruction data are critical not only for the purposes of establishing the required margins of flight safety but also for opera- tional and performance planning. As such, discrepancies in obstruction data or outdated data points (e.g., in data contained in the DOF) will have a detrimental effect on air carrier operational efficiency. The data utilized by performance and procedure design software applies data verification and validation protocols to eliminate obstruction data discrep- ancies or errors. Thereafter, if the end user identifies an error or an omission in the data based on firsthand knowledge, corrections to the operator-specific data can be made in the applications. In addition to using the data for aircraft performance analysis, airlines and charter operators use the analysis of existing or proposed obstructions to conduct a fiscal impact evaluation of the obstacle on their operations. All the potentially affected stakeholders (airport and nonairport) should consider these findings when making local decisions on tall structures. The way that airport users utilize the data and how the data may affect airport operations are some of the key factors that make airports communicating obstruction data changes to those users one of the obstruction management program priorities. State and Local Government State and local governments may serve as additional sources for obstruction data sourcing or verification. As mentioned in the section on FAA Form 5010 data collection, FAR Part 139 airports undergo regular inspections by the FAA, but non-Part 139 certificated airports may have obstruction data collected and maintained as a part of regular state airport inspections. The data collected by state agencies may include estimated or survey-grade locations of controlling obstacles or groups thereof that affect various safety-critical surfaces. Lastly, the local government airport sponsor or the surrounding local jurisdictions may gather data to support the communityâs GIS. The data may include surveyed information on buildings, towers, roadways, and utility infrastructure. Those informational resources may help an airport develop the initial baseline assessment of airspace impacts during obstruc- tion management program development. Moreover, if the airport establishes and maintains airspace surface data in GIS-compatible formats, such data can be shared with the appropri- ate local government entities for a seamless sharing of information related to critical airport airspace needs. Obstruction Data Sourcing/Verification by a State Government The Florida Department of Transportationâs Aviation and Spaceports Office conducts annual airport licensing inspections of all public-use airports. As part of those inspections, the state aviation staff collects data on all the penetrations of FAR Part 77 primary surfaces and on controlling obstacles affecting approach and transitional surfaces. Although the data collected provide only estimates of impact locations and heights (not survey-grade data), these data are valuable in assisting airports in prioritizing airspace safety needs, establishing project priorities for obstruction management, and for updating of Form 5010 data maintained by the FAA.
Obstruction Data Collection and Resources 55 4.2 Collection of Basic Obstruction Data by Airport Staff Basic survey tools such as a clinometer, an instrument used to measure the angle or eleva- tion of slopes, and a hypsometer, an instrument for measuring object height or elevation, may enable airport staff to perform basic obstruction data collection. Using the data obtained with a clinometer and a hypsometer, airport staff can determine the height of the object above the runway endâs elevation and confirm whether the object affects the imaginary surface in question. If the airport intends to collect obstruction data with internal resources, airport staff must have a basic understanding of what FAR Part 77 surfaces apply to each of the applicable runways and their dimensions, as well as their locations and slopes. For example, airport staff can use a basic forestry clinometer tool to verify that the applicable surfaces for each runway are clear. If the surfaces are not clear, the same tool can be used to determine the height of the object above the runway endâs elevation and to establish what slope will clear the controlling obstacle. Additionally, a handheld distance measuring tool, such as a laser rangefinder, can be used to determine the approximate distance to the object from the runway end or from the start of the runwayâs FAR Part 77 imaginary surface. Handheld tools can be used to complete the following: â¢ An approximation of whether a new âpop-upâ obstruction exceeds FAR Part 77 notification or obstruction evaluation surfaces â¢ A determination of a controlling obstacle in a group of objects of the same type (such as trees) â¢ A determination of obstacle removal priorities for an obstruction mitigation project â¢ An inspection of post-obstruction removal conditions to determine the new controlling obstacle Using basic survey tools allows even those airports with limited staff and resources to con- duct a rudimentary obstruction analysis of the airportâs imaginary surfaces. However, the use of handheld tools has inherent accuracy limitations and, therefore, should not be solely relied on to collect individual data points for a comprehensive airport obstruction management pro- gram. Familiarity with the tools is highly beneficial for obstruction spot checks, estimation, and other operationally critical obstruction management tasks; however, if potential obstructions are identified, the situation should be further assessed with more accurate surveying tools.