Understanding Obstruction Evaluation: Ensuring Safe Airspace and Airport Operations

In aviation, ensuring the safety of airspace and airport operations is non-negotiable. Every element within and around the vicinity of flight paths—whether man-made structures like buildings, towers, and wind turbines, or natural features such as tall trees or terrain—has the potential to impact the safety and efficiency of air traffic. To address these risks, the Federal Aviation Administration (FAA) employs a rigorous process known as Obstruction Evaluation (OE). This process is critical for identifying and mitigating hazards to air navigation, ensuring that no obstruction compromises the integrity of flight operations or airport capacity. 

Obstruction evaluation is more than a regulatory requirement—it’s a cornerstone of aviation safety, supporting both operational efficiency and sustainable growth in increasingly urbanized and technologically advanced environments. 

What Is Obstruction Evaluation? → Understanding FAA Obstruction Evaluation 

Obstruction evaluation refers to the FAA’s process of analyzing and determining if a structure could interfere with airspace and the safe operation of aircraft. According to the FAA, this evaluation is essential for ensuring that new constructions or modifications to existing structures don’t adversely affect navigational facilities, airport capacity, or overall aviation safety. 

Why Obstruction Evaluation Matters → The Critical Role of Obstruction Evaluation 

With the ongoing expansion of urban areas and the rise of new technologies, more structures are being built in proximity to airports, including tall buildings, wind turbines, cell towers, and even natural obstacles like trees in critical flight zones. These structures can create potential obstacles for aircraft, particularly during takeoff and landing—two of the most critical flight phases. 

Obstruction evaluation helps mitigate risks by: 

1. Identifying Potential Hazards: Structures deemed a potential risk are thoroughly assessed to understand how they might impact flight operations. 
2. Maintaining Safety: By ensuring structures don’t encroach on critical flight paths, the FAA upholds aviation safety standards. 
3. Supporting Airport Capacity: The evaluation process also considers the potential effects on an airport’s efficiency and capacity, enabling sustainable growth without compromising operational integrity.  

Construction Equipment

Equipment and machinery play a critical role in modern construction projects but require careful consideration during obstruction evaluations near airports. Equipment such as batch plants, cranes, boom trucks, concrete pumps, drilling rigs, and stockpiles often operate at significant heights and can pose temporary hazards to airspace if not properly managed. Additionally, mobile construction areas, haul routes, staging zones, and temporary lighting systems can affect visibility and navigation, particularly during critical flight operations like takeoff and landing. Ensuring these structures comply with FAA height and location regulations is essential for maintaining airspace safety while allowing for efficient project execution. By proactively addressing these factors during the planning and execution phases, developers can mitigate risks to flight safety while maintaining operational efficiency on construction sites.

The Role of Drones and Ground Control Points in Obstruction Evaluation

As obstruction evaluation evolves, drones and ground control points (GCPs) have become valuable tools in the process. These technologies help provide accurate data, increase efficiency, and improve safety during evaluations.

Drones in Obstruction Evaluation

Drones have transformed how obstruction evaluations are conducted, offering precise aerial data that allows for a highly accurate assessment of structures. Here’s how drones are leveraged:

1. Efficient Data Collection: Drones can quickly survey large areas, capturing detailed images and measurements of structures in and around the airport vicinity. This allows for a faster, more comprehensive assessment than traditional methods.
2. High-Resolution Imagery: Drones equipped with high-definition cameras capture clear images and video footage of potential obstructions. This imagery provides critical visual data that allows the FAA to evaluate obstacles with greater precision.
3. 3D Mapping and Modeling: Using LiDAR (Light Detection and Ranging) or photogrammetry, drones can create accurate 3D models of structures and their surroundings. These models provide a detailed visual representation, helping evaluators better understand the structure’s spatial relationship to flight paths and navigational aids.
4. Safer Operations: Drones can reach areas that may be dangerous or impractical for human surveyors, ensuring that evaluation teams can conduct thorough assessments while staying safe.

Ground Control Points (GCPs) in Obstruction Evaluation

In conjunction with drones, ground control points (GCPs) play a vital role in ensuring data accuracy during obstruction evaluations. GCPs are physical markers with known geographic locations, placed strategically within the survey area to serve as reference points for aerial data. Here’s why GCPs are essential:

1. Improved Accuracy: GCPs allow drone operators to calibrate their mapping data, helping ensure that the measurements captured by drones align precisely with real-world coordinates. This accuracy is crucial for obstruction evaluation, where even small discrepancies in measurements could impact airspace safety.
2. Enhanced Data Reliability: By using GCPs, drone-captured data is more reliable and can meet the high standards required for aviation safety. Accurate data helps the FAA make informed decisions about whether a structure poses a risk and should be modified or restricted.
3. Support for Compliance: GCPs also help ensure that mapping data adheres to FAA regulations, as they provide standardized points of reference. This compliance is essential, especially when evaluating large areas with various elevations and complex structures.

The FAA’s Obstruction Evaluation Process

The FAA’s obstruction evaluation process is conducted in several steps, with drones and GCPs often used in the data collection phases. Here’s an overview of the process:

1. Filing a Notice of Proposed Construction: Anyone planning to construct or modify a structure that might pose an obstruction must notify the FAA. This includes any structure exceeding certain height thresholds, such as 200 feet above ground level or in proximity to an airport.
2. Preliminary Screening: The FAA performs an initial review to determine if the structure could affect air navigation or airport operations. In this phase, drones and GCPs can provide essential data for accurate preliminary assessment.
3. Detailed Aeronautical Study: If a potential risk is identified, the FAA conducts a comprehensive aeronautical study. Drones and GCPs are often used in this phase to gather high-precision data on the structure’s height, location, and proximity to flight paths and navigational aids.
4. Public Involvement: In cases where the structure could significantly impact airport operations or the surrounding community, the FAA may seek public comments. This allows stakeholders, including local communities and aviation organizations, to voice concerns or support.
5. Determination of No Hazard or Hazard: After a detailed analysis, the FAA issues a determination. If the structure is deemed safe, it receives a “Determination of No Hazard.” If it poses a risk, the FAA may work with the proposer to adjust the plans, such as reducing the height or relocating the structure.

Why Obstruction Evaluation is Important for Developers and Airport Authorities

For developers, understanding the obstruction evaluation process is crucial before embarking on projects near airports. Engaging with the FAA early in the planning stages, and utilizing drones and GCPs for accurate data, can prevent costly delays and ensure compliance with aviation safety regulations.

For airport authorities and planners, this process is essential for maintaining safe and efficient airport operations while allowing for urban growth. It helps balance the need for new developments with the responsibility of keeping air navigation safe.

The FAA’s obstruction evaluation process is essential to aviation safety, ensuring that structures near airports don’t interfere with air navigation or airport operations. With advancements in drone technology and the use of GCPs, the FAA can conduct more precise and efficient evaluations, safeguarding our skies while allowing for responsible growth and development.

For more information on obstruction evaluation, visit the FAA’s Obstruction Evaluation page.

For guidelines from the Federal Aviation Administration (FAA), take a look at the Advisory Circular (AC) for standards and recommendations for airport design.

Glossary

• Imaginary Surfaces: Surfaces defined in 14 CFR Part 77 and are in relation to the airport and each runway. The size of these imaginary surfaces is based on the category of each runway for current and future airport operations. Any objects which penetrate these surfaces are considered an obstruction and affects navigable airspace.
• Approach Surface: An imaginary obstruction limiting surface defined in 14 CFR Part 77which is longitudinally centered on an extended runway centerline and extends outward and upward from the primary surface at each end of a runway at a designated slope and distance upon the type of available or planned approach by aircraft to a runway.
• Conical Surface: An imaginary obstruction-limiting surface defined in 14 CFR Part 77that extends from the edge of the horizontal surface outward and upward at a slope of 20 to 1 for a horizontal distance of 4,000 feet.
• Horizontal Surface: An imagery obstruction-limiting surface defined in 14 CFR Part 77that is specified as a portion of a horizontal plane surrounding a runway located 150 feet above the established airport elevation. The specific horizontal dimension of this surface is a function of the types of approaches existing or planned for the runway. Appendix A, Glossary A-14
• Primary Surface: An imaginary obstruction-limiting surface defined in 14 CFR Part 77that is specified as a rectangular surface longitudinally centered about a runway. The specific dimensions of this surface are function of types of approaches existing or planned for the runway.
• Transitional Surface: An imaginary obstruction-limiting surface defined in 14 CFR Part 77that extends outward and upward at right angles to the runway centerline and the runway centerline extended at a slope of 7 to 1 from the slides of the primary surface.
• Obstruction: An existing or future object that is of a greater height than any of the heights or surfaces defined in 14 CFR Part 77.23 and 77.25. (Note that obstructions to air navigation are presumed to be hazards to air navigation until an FAA study has determined otherwise.)

This blog is intended for informational purposes only and does not constitute legal or professional advice. It is the responsibility of the reader to fully research and understand all applicable legal, regulatory, and technical requirements for conducting an FAA Airfield Obstruction Survey. This includes, but is not limited to, understanding FAA regulations such as FAR Part 77, obtaining the necessary permissions, clearances, and certifications, and ensuring the accuracy and compliance of all collected data and methodologies. The reader is advised to consult with qualified legal, regulatory, and industry professionals to ensure compliance with all relevant laws and standards. The authors of this document accept no liability for actions taken based on its content.