Electric Vertical Takeoff and Landing (eVTOL) Downwash and Outwash Surveys

Brief overview:
This report presents the results of surveys conducted to measure the downwash and outwash (DWOW) velocities produced by prototype eVTOL aircraft. The research aimed to gather data on DWOW effects to inform vertiport design guidance and safety considerations. Three eVTOL aircraft under 6,500 lbs were surveyed using arrays of ultrasonic anemometers to measure wind velocities at various distances from the aircraft. The results were compared to computer modeling predictions where possible.

The FAA conducted surveys to measure the downwash and outwash (DWOW) velocities produced by prototype electric vertical takeoff and landing (eVTOL) aircraft. This research was needed because eVTOL aircraft designs vary significantly from helicopters, and little data existed on their DWOW effects, which can pose safety risks to people and property near vertiports.Three eVTOL aircraft under 6,500 lbs were surveyed using custom arrays of ultrasonic anemometers placed around simulated vertiport environments. Horizontal sensor arrays measured velocities at various distances from the aircraft touchdown point, while a vertical array captured the velocity profile at different heights. The aircraft performed preset flight maneuvers while wind velocity data was collected.Key findings include:

The report concludes that eVTOL aircraft produce high-velocity DWOW that can pose safety risks beyond vertiport boundaries. It recommends establishing operational "downwash caution areas" where velocities exceed 34.5 mph to mitigate risks.Computer modeling using viscous vortex particle methods was attempted but had limitations in predicting far-field effects for complex eVTOL designs. The report suggests further research is needed on modeling techniques and DWOW mitigation strategies for vertiport design.Overall, this research provides critical data to inform safety guidelines and vertiport design standards as the eVTOL industry develops. The findings highlight the need to carefully consider DWOW effects in urban environments where eVTOLs may operate near populated areas.

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