Understanding Airspace, Objects, and Their Effects on Airports (2010)

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Introduction Appendix A introduced various airspace protection criteria documents, and specified the purpose, function, and application of the broad range of criteria included within those docu- ments. This Appendix describes the interrelationships among criteria. The specialized and var- ied purposes of each of the main groups of criteria can create confusion for airport sponsors, municipal planners, and real estate developers in their application. Discerning how and why the criteria relate to one another, first by general categories and then by specific criteria will facilitate a better understanding of airspace protection. This text briefly diagrams and describes the interrelationships between the four general categories of criteria, and then specific criteria; followed by more detailed discussions of specific issues encountered in the case studies and in research team members’ experience. Interrelationships Among the General Categories of Criteria The criteria are organized in four general categories: 1. Land Use Criteria, for both a. off-airport construction (jurisdiction of the state and/or local municipality), and b. on-airport construction (jurisdiction of the FAA) 2. Airspace Protection Criteria as defined by FAR Part 77 3. Airport Design Criteria 4. Flight Procedure Criteria The relationships between the four general categories are diagrammed in Figure B.1. This dia- gram specifically shows the hierarchical nature of the criteria. At the top are land use criteria— the criteria that lead to the “final say” as to whether or not a structure is permitted to be constructed in a certain manner, location, and height. The other categories and specific types of criteria all support the final land use decision. The letter-keyed arrows on Figure B.1 denote the relationships between the four general cat- egories, described as follows: A. Land use decisions, for both off-airport and on-airport construction, are influenced by air- space protection regulatory criteria, which are defined in FAR Part 77. B. The airspace protection regulatory decisions that result from analyses defined in FAR Part 77 are influenced by a multitude of technical criteria, including those from both flight procedure design and airport design. 78 A P P E N D I X B Interrelationships Among Criteria

Interrelationships Among Criteria 79 Figure B.1. Interrelationships among criteria.

C. Certain individual flight procedure design and airport design criteria influence one another. D. Airport design criteria influence land use decisions on-airport, for airspace and other-than- airspace reasons. Interrelationships Among Specific Criteria Within each of the general categories reside specific criteria governing specific actions and events. These were described in detail in Appendix A. The following paragraphs describe the relationships between the individual criteria: Within Off-Airport Land Use 1. Height zoning ordinances inform construction permits, the final say, by the authority hav- ing jurisdiction, as to whether a proposed structure is legally allowed to be constructed. With respect to height limits, construction permits will generally be approved when the pro- posed height of the structure is equal to, or lower than, the nominal height zoning limit for the parcel or property in question. 2. Proposed construction that exceeds the nominal height limit listed in the height zoning ordi- nance may be granted a construction permit if the authority having jurisdiction approves a variance. Local authorities apply judgment to grant variances based on a variety of factors, including technical, compliance with General Plan, social, civic, political, and others. 3. Height zoning ordinances inform variances in that they provide the basis or starting point for negotiations, and may additionally state limits or other parameters for granting vari- ance approvals. For example, a height limit may be stated as “height limit is 80 feet, with up to 120 feet allowable by variance.” Airspace Protection influences Off-Airport Land Use 4. Height zoning variances should, and often do, require a favorable determination from the FAA as one of many contingencies for approval. For example, “height limit is 80 feet, or as high as 120 feet by variance, which is contingent on a favorable determination from the FAA.” Refer to Task 5 for more detailed information on the FAA OE/AAA process which results in the issuance of FAA airspace determinations. 5. Height zoning ordinances should, and often do, require a favorable determination from the FAA as an additional factor besides a numerical height. For example, “height limit is 80 feet; all construction above 35 feet requires a favorable determination from the FAA.” 6. Height zoning ordinances can reference FAA hazard criteria, in locations near airports where the airport sponsor or other authority has undergone an airspace surfaces mapping effort, and the predicted FAA no-hazard height limits are then relatively well-documented. This is not common, because FAA no-hazard height limits are complex to map and change over time as flight procedures and technologies change. For this reason, many municipali- ties that recognize the FAA OE/AAA process simply rely on the FAA to make determinations on a case-by-case basis at the time each project is proposed (see #4 and #5 above). Mapping the FAA no-hazard height limits can remove some of the uncertainty from the process, and can allow users to assess likely maximum feasible heights more quickly. 7. Height zoning ordinances can reference FAA obstruction criteria, which are simpler geomet- rically. However, these often include only a few of the five types of obstruction criteria defined in FAR Part 77.23, such as imaginary surfaces only, or imaginary surfaces and 500 feet above ground level. In these cases, the height zoning ordinances do not provide comprehensive air- space protection, because heights exceeding hazard standards are in many cases lower than one or more obstruction standard heights, and development can be approved that would not exceed the one or two obstruction standards referenced in the height zoning regulations, but would exceed unmapped hazard standards. 80 Understanding Airspace, Objects, and Their Effects on Airports

8. Height zoning ordinances should, and often do, reference FAA notification criteria, so that developers will be aware of the Federal requirement to submit an FAA Form 7460-1, Notice of Proposed Construction or Alteration, when their proposed structure exceeds any of the FAA notification criteria. Within Airspace Protection 9. The FAA OE/AAA process is a multi-step process involving a structure proponent who pro- poses to construct or alter a structure submitting a Form 7460-1 notice to the FAA, and sev- eral steps of analysis within the FAA and related agencies, and input from local stakeholders where the FAA deems appropriate. It results in the issuance of an airspace determination, which is used in various capacities by various other agencies. 10. FAA hazard criteria inform the FAA OE/AAA process, where the FAA judges whether a pro- posed project would cause a substantial adverse effect to a significant amount of air traffic. If so, the proposal would constitute a hazard to air navigation, and the FAA issues a DOH. If not, the proposal would not constitute a hazard to air navigation, and the FAA issues a DNH. 11. FAA obstruction criteria inform the initial part of the FAA OE/AAA process, where the FAA first analyzes whether a proposed project would exceed obstruction standards. If not, a DNH can be issued. If so, a Notice of Presumed Hazard (NPH) is issued, asking the project sponsor whether or not they would be willing to lower the proposal to a height not exceed- ing obstruction standards. If so, a DNH can be issued. If not, the sponsor may ask the FAA to perform further aeronautical study to assess hazard status. 12. FAA notification criteria guide structure proponents on whether or not they need to file a Form 7460-1 notice with the FAA, to initiate the OE/AAA process. Flight Procedure Design influences Airspace Protection 13. Instrument procedure airspace protection criteria are a component of obstruction criteria, as noted in FAR §77.23(a)(3), defining an obstruction as an object with “A height within a terminal obstacle clearance area, including initial approach segment, a departure area, and a circling approach, which would result in the vertical distance between any point on the object and an established minimum instrument flight altitude within that area to be less than the required obstacle clearance”. 14. VFR airspace protection criteria are a component of obstruction criteria, as noted in FAR §77.23(a)(3) (see note in #13). 15. Instrument procedure airspace protection criteria are the most frequently cited component of hazard assessments. This is because published instrument procedures are often limited to less than ideal parameters based on existing critical obstacles; new obstacles would further degrade the procedures, which would be categorized as a substantial adverse effect. 16. VFR airspace protection criteria can be a component of hazard criteria, especially at airports with few or no instrument procedures, because they protect the main type of flight proce- dures at the airport. Confusion sometimes arises because one component of the VFR airspace protection defined in FAA JO 7400.2, §6-3-8, is geometrically identical to the obstruction standard, civil airport imaginary surfaces for visual-only runways. 17. Airline OEI emergency procedures are not currently a factor in FAA hazard determinations. However, the FAA is currently undertaking a Pilot Program at several airports where OEI protection would factor into hazard determinations. The results of the OEI Pilot Program are expected to be completed and distributed in mid to late 2010. Flight Procedure Design influences Airport Design 18. Runway end siting criteria as defined in FAA AC 150/5300-13, Appendix 2, provide obstacle clearance requirements for two critical points on runways: (1) the threshold, which is the first part of the runway available and suitable for landings, and (2) the departure end of runway Interrelationships Among Criteria 81

or “DER”, the final point on the runway surface for take-off procedures. The clearance geo- metrics for arriving or departing aircraft overflying obstacles are informed by performance tolerances and parameters developed in instrument flight procedure criteria. 19. Similar to #18 above, the clearance geometrics for visual types of runway end siting surfaces are informed by VFR flight protection criteria. 20. Airline OEI protection requires comprehensive obstacle data for the departure corridor. The OEI OIS defined with the runway end siting surfaces requires obstacles that penetrate the surface to be identified and made known to carriers serving the airport. Unlike the other types of runway end siting surfaces, the OEI OIS does not require clearance of the obstacles, and does not dictate the DER position. Airport Design influences Airspace Protection 21. Runway end siting surfaces, inasmuch as several types relate directly to instrument flight procedures’ glideslope and departure climb angles, and threshold and DER locations, could contribute to an obstruction determination under FAR §77.23(a)(3). 22. Runway end siting surfaces, inasmuch as several types relate directly to instrument flight procedures’ glideslope and departure climb angles, and threshold and DER locations, could contribute to a hazard criteria if an object that would affect the surface would, in doing so, cause a substantial adverse effect to a significant amount of air traffic. Airspace Protection influences On-Airport Land Use 23. Filing a 7460-1 is required for all on-airport construction. In its routine analysis, the FAA checks for compliance with airspace protection criteria. Airport Design influences On-Airport Land Use 24. Filing a 7460-1 is required for all on-airport construction. In its routine analysis, the FAA checks for compliance with various types of airport design standard criteria, in addition to airspace protection criteria. The foregoing pages described the interrelationships among airspace protection and related cri- teria, including positive relationships between local permitting processes and airspace protection. However, local construction permit regulations sometimes completely lack, or have inadequate references to, airspace protection criteria and processes; and the airspace protection criteria them- selves can be difficult to understand, even for airport staff and other aviation stakeholders. There can be a breakdown in communication and acceptance of responsibility when problems arise. Conflicts may emerge between a proposal to develop a structure on property and a desire to pro- tect airspace near an airport, or conversely between a proposal to modify or build new airport run- ways and the clearance of existing land uses or structures to accommodate those changes. In either case, greater clarity at the onset could enhance the resolution process as well as the outcome. This goal necessitates a clear understanding of who is responsible for administering and protecting the various airspace criteria, and who benefits from protecting (or not protecting) those criteria— whether the benefits are safety, capacity, economic, or otherwise. There are logical relationships between the objective sought and the appropriate criteria to apply or protect, but to make smart and reasonable tradeoffs in the negotiation process, these relationships will require greater clarity. A Common Misconception There is a problematic misconception that FAR Part 77, Subpart C, Obstruction Standards is the only regulation governing airspace protection. The civil airport imaginary surfaces, presented in §77.25 seem to dominate airport operators’ perception of the airspace around their airport. 82 Understanding Airspace, Objects, and Their Effects on Airports

These surfaces are found in ALP sets, and are therefore an available source of airspace information for airport operators to provide to municipal land use planners and developers. AC 150/5070-6b, Change 1, Airport Master Plans (AC 150/5070) provides airports with guidance and requirements for preparing an ALP. AC 150/5070 states, “the approved ALP will . . . allow the FAA to protect the airspace required for facility or approach procedure improvements” (Page 76). The AC describes how this stated function of the ALP can be fulfilled, with a requirement to include an Airport Air- space Drawing within the ALP drawing set, which is “a drawing depicting obstacle identification surfaces for the full extent of all airport development” (Page 78). The ALP Airport Airspace Drawing requirement focuses on FAR Part 77 imaginary surfaces, but also refers to other criteria that may be relevant. AC 150/5070 asserts (Page 78) that: The drawing will depict the obstacle identification approach surfaces contained in 14 CFR Part 77, Objects Affecting Navigable Airspace. The drawing may also depict other approach surfaces, including the threshold-siting surface, those surfaces associated with United States Standards for Instrument Procedures (TERPS), or those required by the local FAA office or state agency. While these other criteria (in bold) are mentioned in AC 150/5070, they are rarely if ever included in the ALP drawing set. As FAR Part 77.25 imaginary surfaces become the focus, so too are the other criteria within FAR Part 77 and other criteria diminished in their perceived impor- tance in the airspace protection decisions that are made. However, exceeding the height of any of the five types of obstruction standards will classify an object as an “obstruction to air navigation”. Figure B.2 illustrates the five types of obstruction standards defined in FAR §77.23 Airspace Criteria: FAR Part 77 and Beyond Because the ALP requires a drawing depicting FAR Part 77.25 imaginary surfaces, airport managers and land use planners alike tend to rely on these criteria in their planning processes. The other criteria that are critical, but commonly overlooked are: 1. Threshold Siting Requirements in AC 150/5300-13 Appendix 2 2. TERPS Instrument Approach and Departure Procedures 3. One Engine Inoperative Procedures 4. VFR Procedures 5. Other FAR Part 77 Notification and Obstruction Criteria (e.g., Part 77.13 and 77.25) Land Use Planning Criteria: FAR Part 77 The main purpose of FAR Part 77, Objects Affecting Navigable Airspace is to define and pro- vide for notifications and aeronautical studies of proposed objects. Designed as a standard obstruction identification tool, the regulation provides general obstruction identification standards, which focus on providing initial criteria for evaluating whether or not an object or terrain would be an obstruction to aircraft either en-route or on approach to an airport’s runway. As such, the criteria were intended to be mostly consistent with other standard pro- cedure criteria. It is critical to recognize that the FAR Part 77 criteria are meant to be general enough to apply to all airports, therefore standardizing the FAA’s initial evaluation of proposed or exist- ing structures. As such, it serves as a helpful estimate of when an existing or proposed struc- ture will require a more detailed review. Without some method for estimating the critical airspace above the Earth’s surface, there would be a need to evaluate every proposed or exist- ing structure, regardless of height or proximity to an airport. Clearly, this is not a feasible or desirable approach. Interrelationships Among Criteria 83

Figure B.2. Profile view—obstruction standards.

Table B.1 describes the three main functions of FAR Part 77 and describes some of the limi- tations of this regulation. The first limitation identified through the case studies is that project sponsors may fail entirely to submit notification to the FAA even when they meet one of the five notification criteria. In this case, there are no other criteria available at the Federal level to cor- rect for this limitation. Encouraging project sponsors to initiate the FAA OE/AAA process can only occur at the local municipal or county government level. The second limitation found in the case studies is the aforementioned misassumption that the Obstruction Standards found in Subpart C of FAR Part 77 imaginary surfaces are “hard and fast”, or even the only criteria to consider. While this is not always true, it is correct to assume that the FAR Part 77 obstruction standards are designed to be mostly consistent with standard procedure crite- ria. Table B.2 demonstrates how the FAR Part 77 imaginary surfaces relate to those standards. Hypothetically, should an object fall underneath all the surface criteria in FAR Part 77.25, the object would not be a hazard to air navigation. However, as have been found through a number of the case studies presented, there are many cases where other airspace protection criteria are more restrictive, that is, have “lower surfaces” than those in FAR Part 77.25. Under these cir- cumstances, an object may indeed be a hazard to air navigation even though it had not been found to be an obstruction and possible hazard according to FAR Part 77.25. Therefore, the mis- understanding that FAR Part 77.25 is the absolute and only obstruction evaluation criteria can, and has, led to serious conflicts between land use development and local airspace protection around airports. Interrelationships Among Criteria 85 Table B.1. How FAR Part 77 can inform on- and off-airport project sponsors and municipalities about airspace protection. What When Why Gaps/Limitations Notification Requirements When any of the 5 Criteria in §77.13 apply. To promote evaluation of proposals using obstruction standards. • Project sponsors may fail to file notification, if not directed by municipal staff. Obstruction Standards for New or Modified Structures When any of the 5 criteria in §77.23 are triggered by the project sponsor’s notification. To estimate the critical airspace requirements on and around airports. • Sometimes presumed to be “hard and fast”, or even the only criteria. Hazard Evaluation (Aeronautical Study) When a proposed structure exceeds obstruction standards and the project sponsor seeks further aeronautical study in lieu of a reduced structure height. To trigger detailed aeronautical study using procedure design (TERPS) and other criteria. • In many cases, other criteria are either higher or lower than the obstruction standards, and therefore contradict expectations about building height limitations. • Does not evaluate airline emergency departure procedures. FAR Part 77.25 Imaginary Surface Criteria Standard Procedure Criteria 20:1 Approach Surface Standard Descent Rate for Aircraft Visual Approach 34:1 Approach Surface Standard Descent Rate for Aircraft Non-Precision Approach 50:1 Approach Surface Standard Descent Rate for Aircraft Precision Approach 150’ AGL Horizontal Surface Circling Approaches; Missed Approached; and Go-Arounds Primary Surface “Off-Centerline” Approaches No Departure Surfaces Ascent Rates are Typically Greater than Descent Rates Table B.2. FAR Part 77.25 surfaces are consistent with many standard procedure criteria.

For example, the FAR Part 77 civil airport imaginary surfaces do not have any “Departure Surfaces” because it is assumed that aircraft will depart at a greater climb rate than approach descent rate. However, there are cases when a published instrument departure procedure will have a lower climb rate than a given runways descent rate, the following hypothetical scenario demonstrates how such an inconsistency might work: There is be a published instrument departure procedure off Runway 9 that only requires the aircraft to maintain a 200 ft. per nautical mile climb rate, and as such requires airspace protection at a 40:1 sloped OCS from the end of the departure runway. At the same time, the approach to Runway 27 (the same end of the runway) may only be a visual approach, only requiring a 20:1 sloped approach surface, or a non- precision instrument approach with a 34:1 sloped approach surface. In this situation, FAR Part 77 civil airport imaginary surfaces do not “protect” the TERPS departure slope requirement. This challenge leads into the third limitation, that the review provided in an aeronautical study involves review of more detailed, airport-specific review of other criteria. For evaluating the impact of a proposed structure, the U.S. TERPS or other flight procedure design criteria would be used. These criteria can be lower than the imaginary surfaces presented in FAR Part 77.25 and can extend beyond the area covered by the FAR Part 77.25 surfaces. A final limitation is that airline emergency departure procedures, specifically OEI procedures, are not considered in an aeronautical study. For commercial service airports, this may be a critical gap, as airlines must comply with the surface criteria related to these procedures. Degradation of these surfaces due to the construction of incompatible structures can make it economically infea- sible for airlines to carry out certain operations. The general effect is to shorten the usable runway length for departure operations and limit the air service capability (non-stop markets that can be reached by a majority of aircraft operating at the airport) of the airport. A more detailed discussion of OEI follows. In summary, FAR Part 77 airspace protection are useful for early evaluation of proposed or existing structures. The surface criteria in this regulation provide standards that can be applied consistently to every airport. The obstruction standards are useful, as proposed or existing struc- tures that interact with these surfaces will trigger a more in-depth review. However, this leads to the need for additional criteria that directly relate to the operational procedures at a given air- port. There are other limitations that can only be addressed at the airport and/or local jurisdic- tion level. These constraints cannot be resolved by Federal criteria, and therefore can only be rectified with enhanced communication and outreach, local policies, or local regulation.1 Airport Design Criteria: AC 150/5300-13, Appendix 2 The primary purpose of FAA Advisory Circular 150/5300-13, Appendix 2, Runway End Siting Criteria, is the evaluation of the airspace impacts when designing a new or expanded airport or runway. The criteria in AC 150/5300-13 may also be applied when evaluating the impacts of new NAVAIDs on existing structures. The criteria in AC 150/5300-13 provide a much greater level of detail. Unlike FAR Part 77, these criteria include specifications for various airport-specific approach and departure surfaces. Also, references to TERPS criteria, and OEI procedures and other airline or user defined criteria are provided. With this AC, there are particular slopes, which can be directly associated with factors includ- ing aircraft approach categories, airplane design groups, and NAVAIDs. However, much as FAR Part 77 criteria are limited to land use planning (obstruction evaluation and airport airspace analysis), AC 150/5300-13 criteria are considered only when siting a new or expanded runway end, or when evaluating the impacts of new NAVAIDs on existing structures. 86 Understanding Airspace, Objects, and Their Effects on Airports 1For more discussion of airport and local jurisdiction involvement in airspace protection, refer to Tasks 4, 5 and 6.

Because AC 150/5300-13 defines surfaces for a separate purpose, and in some cases with incon- sistent geometries, airport operators that expect decisions related to new or modified airport designs to be based in FAR Part 77 may find major discrepancies with their expectations. A specific exam- ple comes from the case study of Daytona Beach International Airport: During a FAR Part 139 standard certification maintenance inspection, the FAA inspector noted that due a change from visual to GPS non-precision approaches on Runways 7R and 25L, the 20:1 approach slopes as defined in FAR Part 77.25 had become 34:1 due to the newly established non-precision approach procedures. The Airport was already involved in an obstruction removal project but because of this expanded clearance area, a more significant amount of obstruction removal was required. Most of the removal included trees on the airport property, but the tree removal also affected several private proper- ties. The widened primary surface (from 250 feet to 500 feet wide) caused by the new non-precision sta- tus altered the starting position of the associated 7:1 transitional surface, which in turn created a potential conflict with proposed hangar development. The Airport submitted an airspace study checklist to the Airport District Office (ADO) for the pro- posed development and were surprised to learn that 20:1 is the appropriate approach slope for Runway 7R/25L, even though the GPS approaches were published and active. When questioned, the ADO explained that approach slopes are determined by more factors than simply approach types. According to the FAA’s Advisory Circular (AC) 150/5300-13, Airport Design (Change 12, Appendix 2 Runway End Sit- ing Requirements), the use of Runway 7R-25L for only “small aircraft” (maximum certificated takeoff weight <12,500 pounds) classifies it as a “utility” runway. As a utility runway, the 20:1 approach slope is appropriate, whether it has a visual or non-precision approach. Interestingly during this process of soliciting guidance from the Part 139 Inspector, Runway 34 (also changed from visual to GPS non-precision), which is not a utility runway, was also confirmed to have a 20:1 approach slope. The airport expected that Runway 34 would have a greater clearance area and a 34:1 approach slope. Airport staff questioned whether the approach is a “non-solid state” approach (not utilizing any ground based localizer or VOR instruments), allowing for the less expansive 20:1 slope. Once the Airport provided the Part 139 inspector with more detailed information regarding this runway, the determination was made that Runway 34 should have a 34:1 approach slope, as required by AC 150/5300-13 for all non-precision run- ways that serve large aircraft (maximum certificated takeoff weight > 12,500 pounds). This example demonstrates how the surfaces in FAR Part 77 and in AC 150/5300-13 are related to a certain degree, yet the two cannot be assumed as interchangeable. This example did not present a need to explore airspace design criteria, however it is also important to consider that they will play a role in circumstances where approach runway ends have Category II approach minimums or greater (requires TERPS consideration), and when the runway is used for com- mercial air carrier service departures (requires One Engine Inoperative consideration). Figures B.3 through B.7, following pages, illustrate the geometric differences between some of the criteria discussed above, in both plan and profile views. Discussion of OEI Procedures Over the last 10 to 20 years, there has been an ongoing dialogue concerning the protection of airspace associated with airline OEI emergency flight procedures. A fundamental issue is whether OEI procedures should be included in as a criterion in obstruction evaluation process. OEI is not typically a criterion considered by the FAA in OE/AAA evaluations, because OEI pro- cedures are designed by individual airlines, can vary considerably, and can be adjusted to accom- modate new obstacles—although sometimes to a degree that is unacceptable to airlines. Airlines have become increasingly vocal in their call to include OEI considerations in FAA OE/AAA evalu- ations. Airport sponsors and airport users are concerned about the potential impacts to their air- port’s air service capability—the range of markets that can be feasibly reached in a nonstop flight. Degradation of OEI procedures can lead to a shrinking range of air service capability. Some munic- ipalities and the real estate development community are concerned about overly restricting Interrelationships Among Criteria 87

Figure B.3. Plan view—runway approach area.

Figure B.4. Profile view—runway approach area.

Figure B.5. Plan view—departure considerations.

Figure B.6. Plan view—departure considerations.

Figure B.7. Plan view of VFR protection and instrument procedure protection.

developable heights on private land. As a result of these constituencies and concerns, there is less certainty in obstruction evaluations for OEI procedures than in other obstruction criteria (TERPS, FAR Part 77, AC 150/5300-13, etc.). Questions that are being debated include: ✈ Is OEI a safety issue, capacity/delay issue, or an airline economic issue? ✈ Is there an adverse affect to aviation? • Reduced effective length of useable runway • Increased airline costs / reduced range capability from resulting weight penalties • Reduced passenger level of service • Runway use impacts and associated ATC complexity and delay ✈ Is a substantial amount of air traffic affected? • Frequency of a weight penalty event • Amount of the weight penalty ✈ How does it define the air service capability of an airport? ✈ Is it an airport/runway design issue or an airspace/air traffic issue? ✈ How to protect for OEI when some airlines may have a slightly different OEI procedure for a specific runway/aircraft? For example, straight vs. turning. Appendix A identifies a number of regulations and criteria concerning departure and OEI procedures (see 2.1.8, 2.2.1, 2.2.2, 2.3.1, and 2.3.5). This section discusses a number of the issues regarding OEI procedures and their comparison with other airport design criteria routinely con- sidered in the OE/AAA process, and airport planning and design activities. OEI Obstacle Identification Surfaces The obstacles considered by the airlines in their OEI calculations are taken from a variety of industry sources. • Airport Obstruction Charts (AOC) produced by the National Oceanic and Atmospheric Administration (NOAA) have traditionally been the primary source obstacle data and major airport features such as runways, taxiways, buildings, etc. NOAA field-surveys most airports on a cycle of approximately 5 to 10 years, and makes the AOCs and their accompanying aeronau- tical data sheets (ADS) available through the National Aeronautical Charting Office (NACO) both in paper and online electronic formats. AOCs are generally a very accurate representation of the airport and surrounding obstacles at the date of the survey. As years pass between sur- veys, there may be changes to runways and obstacles that would not be reflected on an older AOC. In the coming years, NOAA’s role in conducting and charting airport obstruction sur- veys will be replaced by surveys by others (including airport sponsors, and private surveying firms) conducted under ACs 150/5300-16, -17, and -18. • NACO also maintains a nationwide database of obstacles known as the Digital Obstacle File (DOF). The DOF is built up from various sources, including field surveys, and new buildings receiving a DNH and/or reported by building sponsors filing Form 7460-2, Notice of Actual Construction. It is updated on a 56-day cycle, therefore it may contain newer obstructions that have been introduced since the last AOC was surveyed. However, it has been our experi- ence that some of the data are inaccurate (off location laterally or in height), and some obsta- cles have either been removed or were never built. • Obstruction surveys conducted by the airport sponsor are another source for such information. • FAA AC 150/5300-13, Appendix 2, provides guidance for developing survey data within a wide 62.5:1 OEI OIS for reporting obstacles to air carriers for consideration in their OEI procedure development. This surface is required to be depicted on ALPs. • AC 150/5300-18 provides guidance for conducting an overall airport-wide photogramme- try survey, including documentation of obstacles not only in the OEI departure area but Interrelationships Among Criteria 93

also all around the airfield, largely duplicating the process of developing an AOC. The lat- eral “splays” and lengths of these surfaces cover a much wider area than is typically used in an individual airline OEI procedure development. However, because of the various lateral splays used by different airlines and the potential inclusion of slight turns in an OEI proce- dure, a larger OIS for use in surveys is appropriate (see Figure B.5). It is important to note that the 62.5:1 slope to the OIS is an obstacle identification surface and not considered by the FAA to be an OE/AAA obstruction or hazard criteria surface, nor a run- way end siting surface that must be clear of obstacles. OEI Procedures Are Airline-Specific FAR Part 25 establishes the performance requirements for the certification of turbojet aircraft. Through this certification, procedures and performance data are established by the aircraft man- ufacturer. Using this data, airline operations engineering departments develop specific emer- gency flight procedures designed to provide adequate obstacle clearance in the event of the loss of power to one engine. A unique OEI procedure must be designed for each runway heading at each airport the airline serves. Pilots review the OEI procedure for a particular runway as they are preparing for departure, because they must react within seconds in the event of loss of power. While the FAA must approve OEI procedures, because they are developed by each individual airline, they can vary from airline to airline, even for the same aircraft departing the same run- way. FAA provides some guidance for the development of these procedures in FAA AC 120-91 (discussed in Task 2). A first step in providing adequate obstacle clearance for OEI procedures is to identify the obstacles that need to be considered. Obstacles within an obstacle accountability area (OAA) or “splay” from the runway end through the intended OEI flight path are considered by the proce- dure designer. The obstacle identification surface (OIS) within this splay is 62:5:1 for two engine turbojet aircraft. (Increased slopes are considered for 3- and 4-engine aircraft.) Many U.S. carriers utilize FAA AC 120-91 splay to determine the lateral splay. Most foreign flag carriers, many cargo carriers, and some U.S. carriers utilize the ICAO OEI splay. (ICAO Annex 6 to the Convention on International Civil Aviation, Operation of Aircraft, Eighth Edi- tion, July 2001.) Some airlines have developed their own custom OEI splay. A comparison of some of these OEI procedure and OIS splays is presented on Figure B.5. The procedure designer has some latitude to have a slight turn in the flight path or course adjustment to avoid specific obstacles, but airline policies differ on how close to the runway end / how soon after liftoff / at what minimum altitude such a course adjustment can feasibly commence. Generally, turns are undesirable because (1) aeronautical lift decreases with an increased bank angle of the aircraft, and (2) a turn represents a potential complexity or distraction in an emergency situation that is likely to be stressful. TERPS vs. OEI Requirements FAA AC 120-91, Airport Obstacle Analysis, Paragraph 7(a) provides the following description of TERPS vs. OEI requirements: Standard Instrument Departures (SID) or Departure Procedures (DP) based on TERPS or ICAO Pro- cedures for Air Navigation Services—Aircraft Operations (PANS-OPS) are based on normal (all engines operating) operations. Thus, one-engine-inoperative obstacle clearance requirements and the all-engines- operating TERPS requirements are independent, and one-engine-inoperative procedures do not need to meet TERPS requirements. Further, compliance with TERPS all-engines-operating climb gradient require- ments does not necessarily assure that one-engine-inoperative obstacle clearance requirements are met. 94 Understanding Airspace, Objects, and Their Effects on Airports

FAA OE/AAA Process and OEI Typically, OEI is not considered in the OE/AAA analysis process because FAA has histor- ically taken a position that they have no legal basis to declare a hazard based on what is osten- sibly a solely economic impact to airlines. Airlines submit negative comments when an OE case is circularized, and FAA paraphrases them in the DNH but notes that unless TERPS or other criteria are exceeded, economic impact to an airline, in and of itself, is not grounds for a hazard determination. In recent years, there has been FAA acknowledgement that OEI is an issue that needs to be addressed. The FAA has established a pilot program at five airports reviewing methods that could be used to incorporate OEI protection. Effect of Obstacles on Airlines The OEI procedure designer at the airline must review the obstacles identified and ensure that the calculated balance between thrust, lift, and weight of the aircraft permits adequate obstacle clearance during an OEI event. In addition to weight and obstacles, many other variables are considered in these calculations such as aircraft performance, runway length, temperature, winds, runway gradient, runway condition (rain/snow), range, reserve fuel requirements, etc. If the aircraft is deemed too heavy to clear an obstacle, some combination of passengers, fuel, and cargo are removed to reduce the overall weight of the aircraft. This is known as a “weight penalty”. Weight penalties can have a substantial negative financial impact on the flight, render- ing it economically infeasible, or may make the flight technically infeasible. In many cases, an obstacle (above the 62.5:1 OIS) will have no negative OEI-related effect on the departure performance calculation for a specific airline/aircraft/city combination. In some cases this is true of obstacles that are as high as the TERPS departure surface (typically 40:1). On the other hand, even a small penetration of a 62.5:1 surface by an obstacle could result in weight penal- ties. The amount of a weight penalty and frequency of occurrence can be considerations when an airline is evaluating the response to weight penalties, such as: removal of passengers and/or cargo from an aircraft, refuel at interim stopover airport, change to a different type of aircraft, cease ser- vice to particular markets. Because of the many variables and considerations there is not yet agreement on standardized surface gradient above the 62.5:1 that can completely protect for all OEI related weight penal- ties. The fact that each airline could have a slightly different splay and gradient requirement has complicated the process of developing common OEI airspace protection criteria. Effect on Airport Users If significant weight penalties result from obstacles within the OEI OAA, an airline will need to determine whether it is (1) technically feasible to operate the aircraft to a specific market given potential limitations on fuel loads and (2) financially feasible to provide air service to a specific city given the loss of passenger or cargo revenue. In cases where such weight penalties may be infrequent additional costs of rerouting displaced passengers and cargo are considered by the airlines in determining the financial feasibility of the market. The result of such weight penalties can affect the air service capability of an airport by limit- ing the types of aircraft or the markets served from an airport. In the Case Studies, the air service impacts from OEI obstacles tended to be limitations on long-range domestic air service and trans-oceanic air service. Interrelationships Among Criteria 95

Effect on Airports The effect of OEI obstacles that result in weight penalties is the equivalent to reducing the run- way length available. While the overall length of a runway can comply with FAA airport design criteria and aircraft manufacturers recommendations to accommodate a critical aircraft and provide the range capability to serve distant markets, obstacles off the end of the runway can effectively reduce that length. The 40:1 gradient of the departure runway end siting surface criteria in FAA AC 150/5300-13 (see 2.2.1) is intended to provide clearance from the runway ends to surrounding obstacles, for standard all-engine departures climbing at a rate of 200 fpnm. The threshold siting surface closely relates to the TERPS departure surface discussed above. As previously mentioned, the TERPS departure surface is based on all engines operating. Therefore, the threshold siting surface may not provide full consideration for specific aircraft OEI performance and resultant air service capability of a runway. For airports with multiple runways, an airline or pilot may request a specific departure run- way to minimize weight penalties that could affect runway use, or the pilot’s voluntary selection of a departure runway that is nonstandard. Depending on the obstructions in the OEI OAA for each runway, the runway with the minimum weight penalty may or may not be the longest run- way at the airport. In some cases the runway that minimizes weight penalties may conflict with the standard runway use configuration at the airport such as: ✈Use of a primary arrival runway for departures ✈Use of an intersecting runway ✈Use of a runway that operationally conflicts with the current arrival and departure flows ✈ Creation of increased workload and complexity for ATC staff by changing taxi routes for a specific aircraft or group of aircraft Such operational complexities can result in increased ATC complexity, decreased airfield capacity, and increased aircraft delays. Protecting for OEI As previously mentioned, the FAA is conducting a pilot program aimed at evaluating meth- ods for protecting for OEI procedures at five airports. In BOS, a composite map was developed incorporating a number of the specific airline OEI procedure splays. In such cases, it may not be feasible to protect for the 62.5:1 surface gradient because of existing obstructions. In these cases, the existing obstruction becomes the “controlling obstacle” that results in a higher surface gra- dient (steeper slope), as was the case at SJC. See Figure B.6 for a profile view of ideal vs. actual OEI surfaces based on existing obstacles. An appendix in the Final Report describes in more detail how some airports are incorporating OEI surface protection into their overall airspace protection programs in the “OEI Pilot Program.” 96 Understanding Airspace, Objects, and Their Effects on Airports