CHAPTER 1
Introduction

Airports consistently face challenges in coordinating with external entities, such as municipalities, private companies, and the public, to address verified obstructions to air navigation. Mechanisms and tools are available for airports to assist in creating an environment free of obstructions such as the Airport Data and Information Portal (ADIP, https://adip.faa.gov/), which manages data specific to an airport, the Obstruction Evaluation/Airport Airspace Analysis (OE/AAA, https://oeaaa.faa.gov/) web portal that provides tools and resources to retrieve aeronautical study data, and Part 77 of Title 14 of the CFR that provides standards and processes for obstructions. Even when obstructions are verified through inspections by state aeronautical agencies or additional analysis, airports often must negotiate with landowners or other stakeholders to remove obstructions that fall outside the airportʼs jurisdiction (e.g., obstructions on private land or in a neighboring municipality). The need for external coordination may result in delays, additional costs, or legal action to address the obstruction, such as eminent domain. There is currently no single resource that synthesizes how airports address these situations.

Objects that are considered obstructions under Part 77 may pose concerns for aviation safety and operational efficiency. These obstructions, such as buildings, trees, communication towers, or terrain, can penetrate protected airspace surfaces established to ensure safe aircraft operations during takeoff, landing, and approach phases. Understanding the nature of airport obstructions, the responsibilities of airport authorities, and the frameworks in place to manage them is essential for effective mitigation, especially for obstructions located off airport property.

The FAA can identify hazards, but only local governments have the authority to enforce height and use restrictions within their boundaries. So, airspace protection involves collaboration among airports, local communities, governments, and users. This synthesis identifies mechanisms and processes that airports have implemented to protect the navigable airspace around airports.

Synthesis Objectives

The objective of this synthesis was to collect information on the mechanisms airports use to address obstructions outside the airport boundary. The audience for this synthesis is airport sponsors, local permitting authorities, state aviation officials, and other non-airport stakeholders.

Synthesis Scope and Approach

This synthesis provides a comprehensive overview of the practices airports use to address off-airport obstructions, with a focus on their connections with local and state agencies and the FAA, engagement with landowners, and the resources the airports use. The survey examines how airports leverage existing resources, such as state aviation personnel, the OE/AAA website,

and Advisory Circulars (ACs). The survey also investigates the outreach airports make with surrounding landowners to develop relationships and provide an understanding of obstructions and, when needed, mitigation measures. Costs to study and mitigate obstructions can be significant, especially at smaller airports, and the synthesis summarizes how airports fund various costs associated with off-airport obstructions.

Airports have implemented various solutions to address obstructions. The synthesis identifies the solutions airports are using, ranging from removing or altering the obstruction to runway changes, such as displaced thresholds, increased minimum approach altitudes, or the elimination of nighttime instrument approaches.

To gather this information, the synthesis employed a literature review, an online survey of airports of various sizes and locations, and interviews with selected airports to develop case examples. Finally, the report highlights knowledge gaps and provides suggestions for future studies to address these gaps.

Synthesis Organization

This synthesis is organized into several chapters that provide a structured overview of how airports of varying sizes address off-airport obstructions.

Chapter 1 introduces the project by presenting the background, objectives, scope, and approach of the synthesis. It sets the stage for the rest of the synthesis by outlining the impact of obstructions on airports, the key issues examined, and the methods used to gather information.

Chapter 2 provides a literature review of existing research, reference materials, and industry practices related to obstructions and Part 77 surfaces. This chapter highlights key themes and findings from published sources, including regulations, Advisory Circulars, prior research studies, and technological tools currently in use. The literature review establishes a foundation for understanding current knowledge and for identifying the practices this synthesis seeks to address.

Chapter 3 presents the survey findings completed by airports. This chapter summarizes the responses and offers insight into the range of practices and experiences across different airport sizes.

Chapter 4 presents case examples from interviews conducted as part of research for this synthesis. This chapter offers insights drawn from interviews with selected airports, highlighting their specific approaches to communication, outreach, airport impacts, and costs associated with off-airport obstruction mitigation. It includes both the key themes that emerged from the interview questions and context-specific information about the participating airports, and identifies specific airport projects addressing obstructions that supplement the broader survey results.

Chapter 5 is the final chapter of the synthesis and provides a summary of insights gained from the literature review, survey responses, and case example interviews, offering a perspective on current mechanisms airports are using to address off-airport obstructions. It also identifies gaps in the state of practice, areas where information is limited, or inconsistencies in how obstructions might impact safety or operations. Based on these identified gaps, suggestions for future research are proposed, focusing specifically on areas where additional insights could enhance understanding and improve outcomes. The chapter emphasizes that research suggestions are grounded in the evidence gathered throughout the synthesis and are only suggested where clear needs for further exploration have been identified.