There are more solutions than obstacles. Nicolas Zart
Aviation Downwash & Advanced Air Mobility: Insights from Georgia Tech’s Prof. Marilyn Smith
The future of urban air mobility is taking shape in research labs and engineering centers across the world. But as electric vertical takeoff and landing (eVTOL) aircraft edge closer to commercial reality, new challenges emerge—none more critical than understanding aviation downwash and its impact on safety, infrastructure, and design.
On a recent episode of The Ways We Move podcast, host Nicolas Zart sat down with Prof. Marilyn Smith, Director of the Vertical Lift Research Center of Excellence and professor at Georgia Tech’s Daniel Guggenheim School of Aerospace Engineering. With decades of experience in unsteady aerodynamics and computational aeroelasticity, Prof. Smith provided a deep dive into the mechanics of downwash and why it matters for the next generation of flight.
What Is Downwash and Why Does It Matter?
Downwash refers to the powerful stream of air pushed downward by a rotor, whether on a helicopter, drone, or eVTOL. “In the simplest sense, downwash is the velocity generated by the rotor, coming down on you,” Prof. Smith explains. While the concept is straightforward, its implications are far-reaching. Downwash can endanger people and property below, stir up debris, and even cause accidents, such as brownouts and whiteouts that have led to tragic helicopter incidents.
The Complexity of eVTOL and Multirotor Downwash
Unlike traditional helicopters, eVTOLs often feature multiple rotors in close proximity. This brings new aerodynamic interactions: “Depending on how close multiple rotors are together, their wakes can interact—sometimes negating, sometimes exacerbating negative effects,” says Prof. Smith. These interactions aren’t just theoretical; they affect everything from vehicle control to the lifespan of rotor blades, especially in harsh environments like deserts.
Advanced computational tools, including Navier-Stokes simulations, are now essential for modeling these complex flows. Research at Georgia Tech and other leading institutions is helping manufacturers and regulators understand how downwash behaves in real-world urban environments.
Vertiport Design and Urban Operations
As AAM moves from concept to city streets, vertiport design becomes critical. Unlike remote heliports, urban vertiports are surrounded by buildings, people, and unpredictable wind patterns. Prof. Smith highlights how downwash can bounce off buildings, creating hazardous recirculation zones and complicating takeoff and landing procedures.
The FAA has recognized these challenges, evolving vertiport guidelines in consultation with the rotorcraft community. The merger of heliport and vertiport standards is a step toward safer, more practical infrastructure for AAM.
Safety, Simulation, and the Path Forward
Safety remains the top priority for AAM adoption. “Safe is a relative term,” Prof. Smith notes, pointing out that safety considerations range from people on the ground to vehicle reliability and control systems. Ongoing research at Georgia Tech includes experimental testing of multirotor aircraft near obstacles, providing critical data for both designers and regulators.
Another key takeaway: the importance of scalable solutions. As AAM expands to include passenger vehicles, drones, and cargo delivery, adaptable approaches to downwash modeling and mitigation will be essential.
The Role of Research and Collaboration
Prof. Smith’s conversation with Nicolas Zart underscores the collaborative spirit driving AAM innovation. With input from academia, industry, and regulators, the sector is moving toward safer, smarter, and more sustainable flight.
As Prof. Smith concludes, “The technology to build these vehicles is here. Now, it’s about operations and safety—especially as we bring flight into the heart of our cities.”