Abstract

As part of the Federal Aviation Administration’s (FAA) effort to establish vertiport design guidance for facilities intended to accept powered lift and special class rotorcraft, it is of growing importance to determine the risk factors related to vertical takeoff and landing (VTOL) operations and how to mitigate them.  The airflow generated from the aircraft’s rotors/propellers during takeoff and landing, known as downwash and outwash (DWOW), can pose significant risks to people and property in the vicinity of aircraft operations. Downwash is the vertical, downward flow of air produced by rotors/propellers while outwash is the lateral, radial, outward airflow that occurs as the downwash contacts the landing surface. The negative impacts of DWOW may be exacerbated at vertiport locations in urban areas where high-volume, high-tempo operations are proposed because of the dense populations and higher throughput in those areas. However, current research on the effects and mitigation of DWOW is limited. This report describes the collection and analysis of VTOL DWOW data and the need to mitigate associated risks.

The most reliable way to obtain eVTOL DWOW data is from full-scale aircraft surveys. This research measured the DWOW of three prototype eVTOL aircraft for their maximum velocity at various locations on a vertiport. A ground-level array and a vertical array of ultrasonic three-dimensional anemometers were used for collecting the DWOW wind velocities. The DWOW surveys were performed at various times and locations and conducted under daylight visual meteorological conditions. DWOW wind data were collected at each anemometer location on the ground or vertical sensor array. The aircraft pilots performed several preset maneuvers within the bounds of their respective aircraft flight envelopes. Analysis of the results included maximum instantaneous velocities, moving means and moving standard deviations based on a 3-second time frame, and a 3-second moving 95^th percentile. The survey measurements for the three prototype eVTOL aircraft included in the research were compared to viscous vortex particle method modeling and simulation where possible.