Impact of eVTOL Aircraft Outwash on Vertiport Design

Recent Federal Aviation Administration research has revealed significant safety concerns regarding electric vertical take-off and landing (eVTOL) aircraft operations. According to their December 2024 report “Electric Vertical Take-off and Landing (eVTOL) Downwash and Outwash Survey,” these aircraft can generate downwash and outwash (DWOW) forces equivalent to hurricane-force winds, exceeding current safety threshold guidelines.

This finding has significant implications for the future of urban air mobility (UAM) infrastructure, particularly in vertiport design and operations. The FAA draws particular attention to the potential hazards, citing historical incidents where similar effects from helicopter rotor wash resulted in injuries and fatalities to bystanders. The report serves multiple purposes: it highlights the critical differences between helicopter and eVTOL downwash effects, emphasizes the need for specialized safety considerations, and aims to inform the development of vertiport infrastructure as the industry prepares for widespread eVTOL adoption. While the findings do not constitute formal regulation, they are intended to initiate discussions among key stakeholders, including manufacturers, operators, and regulators.

Outwash Characteristics of eVTOL Aircraft

The emergence of electric vertical take-off and landing (eVTOL) aircraft has introduced new challenges in understanding and managing outwash effects. This rapidly moving air spreads outward when rotorcraft operate near the ground. While traditional helicopters and eVTOL aircraft generate outwash that can impact bystanders and infrastructure, their characteristics differ substantially due to fundamental design variations.

With their single main rotor configuration, traditional helicopters produce well-documented and predictable outwash patterns that the aviation industry has thoroughly studied. In contrast, eVTOL aircraft typically employ multiple rotors in varied configurations, resulting in more complex and less predictable outwash behavior. These unique rotor layouts heavily influence the shape and strength of eVTOL outwash, creating aerodynamic interactions that may not align with conventional helicopter operational experience.

Regulatory bodies, including the Federal Aviation Administration (FAA), have recognized these distinctions and are adapting their guidelines accordingly. FAA's Engineering Brief (EB) No. 105A includes updated vertiport design standards addressing eVTOL outwash effects, with vertiport geometry and aircraft parking guidance modifications. Similarly, organizations like the UK Civil Aviation Authority (CAA) are conducting studies to understand these differences better and ensure ground personnel safety.

eVTOL Outwash Effects Regulations

The Federal Aviation Administration (FAA) has established comprehensive guidelines for vertiport infrastructure to support Advanced Air Mobility (AAM) and electric vertical take-off and landing (eVTOL) operations. These requirements are detailed in the FAA's Engineering Brief (EB) No. 105A, released on December 27, 2024. The brief supplements existing heliport design standards while addressing the unique characteristics of eVTOL aircraft. The regulatory framework focuses on several critical infrastructure elements. First, vertiports must be designed to accommodate aircraft with three or more propulsors, distinguishing them from traditional helicopter facilities. The classification system aligns with existing hospital and prior permission required (PPR) heliport standards, ensuring integration with current aviation infrastructure.

The FAA mandates establishing a downwash/outwash caution area (DCA) to protect personnel and equipment from high-velocity airflow during take-off and landing operations. This requirement demonstrates the FAA's emphasis on operational safety in urban environments. The guidelines also specify requirements for parking positions, which must be equivalent in size to the Final Approach and Take-off (FATO) area. These positions must be engineered to withstand dynamic loads during hover and air taxi operations, ensuring structural integrity throughout various flight phases.

Vertiports must incorporate appropriate electrical infrastructure to support these operations, including charging systems with compatible plugs. Additionally, integrating advanced surveillance technologies and uncrewed traffic management (UTM) systems is essential, particularly for remotely operated or autonomous aircraft.

The FAA emphasizes the importance of coordination between vertiport developers and existing airports. This collaboration ensures proper site selection and integration with current airport operations, maintaining safety and efficiency in increasingly complex airspace environments. These comprehensive requirements aim to facilitate the safe development of urban air mobility infrastructure while addressing the unique challenges posed by eVTOL operations.

Urban-Air Port has developed technologies that reduce the speed and extent of downwash during take-off and landing, addressing the challenges posed by the violent and unpredictable nature of eVTOL outwash. Urban-Air Port’s vertically elevated landing platform uses a multi-patented design to disrupt dangerous airflow patterns produced by eVTOL rotors. This significantly reduces the speed and outward propagation of downwash and outwash. By preventing the formation of strong vortical cells, their “Vertical Airfield” technology helps safeguard ground personnel and nearby infrastructure. Unlike traditional flat, ground-based vertiport layouts, Urban-Air Port’s solution is engineered to contain and diffuse the rotor wake, mitigating hazardous wind velocities that can otherwise propagate hundreds of feet beyond the landing pad. 

Because outwash is suppressed at its source, Urban-Air Port’s approach maintains safe operating conditions without requiring additional power from the aircraft itself during hover. This translates into more minor real estate requirements while preserving throughput, meaning more efficient operations and faster turnaround times. As a result, the urban integration of eVTOLs can become more practical and profitable, especially in dense metropolitan environments where space is limited and high-tempo aircraft movements are anticipated.

Location Selection in Urban Areas

When selecting vertiport locations in densely populated urban areas, several primary considerations must be addressed to minimize the impact of outwash on nearby structures and communities. One significant factor is establishing a systematic approach to vertiport site selection. The Mineta Transportation Institute (MTI) white paper "Land Use Analysis on Vertiports Based on a Case Study of the San Francisco Bay Area"  details a method that combines safety, accessibility, and equity criteria within a matrix and then employs Geographic Information Systems (GIS) to analyze relevant parameters at different priority levels. 

This workflow starts with identifying “high-priority” non-negotiable factors (such as aviation safety constraints or clear flight paths), followed by “medium” and “low” priorities that address broader needs like local zoning and community input. Sites that satisfy all priority levels pass as optimal vertiport locations, whereas failure to meet high-priority requirements rules locations out entirely.

By modeling these criteria in GIS, planners can see how local factors—like residential preferences, commercial zoning, or nearby transit stations—might affect vertiport feasibility. This ensures consistency in site selection across an entire region yet still accommodates localized conditions13. This flexible framework also encourages employing 3D visualizations, especially before finalizing a site, to engage communities and detect any unforeseen impacts promptly.

Environmental Impacts

Federal, state, local, and tribal regulations address the environmental impacts of eVTOL aircraft, particularly outwash effects such as noise and air quality. Noise management, in particular, involves overlapping legal authorities. While the FAA generally holds the authority over the operation of eVTOL aircraft, state and local governments play a significant role in zoning and permitting processes related to ground-based infrastructure. These local authorities may set specific vertiport siting requirements to mitigate noise impacts on surrounding communities.

Sustainability is another critical factor in the environmental footprint of eVTOL operations. Ensuring the sustainability of drones and AAM systems requires focusing on clean energy sources, reduced emissions, and efficient infrastructure. Continuous planning and assessment are necessary to align these technologies with sustainability goals and minimize their environmental impact on communities.

Regulatory frameworks specific to the environmental impacts of eVTOL aircraft are still in development. For instance, the European Aviation Safety Agency (EASA) is working on creating new standards for environmental protection, including noise and emissions, as the existing standards under the Chicago Convention do not fully cover VTOL capabilities.

Strategies for Urban Planners to Engage Communities about eVTOL Noise

Urban planners are crucial in integrating electric vertical take-off and landing (eVTOL) aircraft into urban environments. Addressing community concerns about noise and safety is essential for successfully implementing this innovative technology. A comprehensive approach combining community engagement, transparent communication, and innovative noise mitigation techniques can help build trust and address residents' concerns.

Community Engagement and Communication

Community engagement is the cornerstone of building trust with residents. Urban planners should:

• Involve the community early in the decision-making process
• Maintain open lines of communication throughout the planning stages
• Organize regular town hall meetings, workshops, and surveys
• Implement feedback mechanisms such as online platforms or dedicated hotlines
• Leverage social media platforms and local media outlets for broader outreach

Transparent communication is essential for informing residents about the potential impacts of eVTOL noise and safety measures. Providing clear, accessible information about anticipated noise levels, mitigation steps, and the benefits of eVTOL integration can help alleviate concerns.

Innovative Noise Mitigation Techniques

To reduce the noise impact of eVTOL aircraft, urban planners should consider:

• Incorporating noise control into urban planning and design
• Integrating noise criteria and objectives into land use and zoning decisions
• Promoting mixed-use, compact, and walkable urban forms
• Enhancing the natural and built environment with green and blue infrastructure
• Learning from best practices and examples of noise control in urban planning worldwide
• Enhancing the soundproofing of buildings near vertiports

Addressing Safety Concerns

To address safety concerns related to eVTOL aircraft, urban planners can:

• Organize public forums and workshops with experts to explain safety measures
• Conduct pilot programs and demonstrations of eVTOL operations
• Implement participatory planning approaches to involve community members in decision-making
• Use surveys and feedback mechanisms to gather public opinion and incorporate it into planning decisions

Public Perception and Acceptance

The European Union Aviation Authority's (EASA) survey on public acceptance of advanced air mobility systems highlights the importance of addressing noise concerns for societal acceptance of eVTOL aircraft. The survey identified noise as a significant concern, influencing legislation for vertiport infrastructure and aircraft design. By implementing these strategies, urban planners can effectively engage communities, address concerns about eVTOL noise and safety, and pave the way for the successful integration of this innovative technology into urban environments.

Electric Vertical Takeoff and Landing (eVTOL) Downwash and Outwash Surveys.pdf3.40 MB

EB_105A_Engineering Brief No. 105A, Vertiport Designs.pdf1.69 MB

Land Use Analysis on Vertiports.pdf5.99 MB