Recent events have highlighted the problem of helicopter downwash and outwash (DWOW) causing property damage, injuries and even death. However, pilot training on DWOW is lacking, the measured data on helicopters DWOW is lacking, reporting is lacking, and modeling and simulation tools are lacking. New types of multi-rotor VTOL aircraft (i.e. AW609 and AAM) have higher disk loading and higher directionality.
Several webmeetings have been held, and a webinar presentation by the UK Civil Aviation Authority (CAA) on their recent publication, CAP3075: Protecting the Future: Trials and Simulation of Downwash and Outwash for Helicopters and Powered Lift Aircraft, was held on April 29, and posted on the VFS YouTube channel.
VFS is holding a workshop as part of Forum 81 to examine these issues and decide if VFS should take future steps to improve the understanding of these issues. The Forum 81 DWOW workshop is on Monday, May 19, 2025.
The Society is also creating a reference library of studies, reports, papers and other documents helpful to understanding the phenomenon for vertical flight aircraft. Some initial documents are posted on this page in the right column: →
VFS is building a comprehensive Downwash and Outwash Library (under construction) — new!
Questions?
Contact VFS Infrastructure Advisor Rex Alexander for more information.
Downwash-Outwash References
US FAA & Related
- Engineering Brief No. 105A, Vertiport Design, Supplemental Guidance to Advisory Circular 150/5390-2D, Heliport Design, US FAA, Dec. 27, 2025
- Electric Vertical Takeoff and Landing (eVTOL) Downwash and Outwash Surveys, US FAA, Dec. 20, 2024
- Rotorwash Analysis Handbook, Volume I — Development and Analysis, FAA, June 1994
- Rotorwash Analysis Handbook, Volume II — Appendixes, FAA, June 1994
UK CAA & Related
- UK CAA Downwash/Outwash webinar, VFS, April 29, 2025
- CAP3075: Protecting the Future: Trials and Simulation of Downwash and Outwash for Helicopters and Powered Lift Aircraft, UK CAA, April 1, 2025
- CAP3075-related simulation videos, Sophrodyne, April 1, 2025
- CAP1264: Standards for helicopter landing areas at hospitals, UK CAA, April 2024
- Do eVTOL Aircraft Create an Inherently More Problematic Downwash than Conventional Helicopters?, Sophrodyne, Sept. 5–7, 2023 (ERF 49)
US DoD & Related
- Rotorwash Operational Footprint Modeling, US Army, 2014
- CH-47D Tandem Rotor Outwash Survey, US Navy, 2011 (VFS Forum 67)
- Rotorwash Prediction Using an Applied Computational Fluid Dynamics Tool, US Army, May 2004 (VFS Forum 60)