The UK Civil Aviation Authority (CAA) has published CAP2576, a paper which presents an initial view of the effects of downwash for the safe operation of eVTOL air vehicles.
“The work is intended to provide a basis for further debate and discussion between manufacturers, operators and regulators,” according to the UK aviation regulator. “This should allow them to assess and, where needed, begin to address some of the issues found by this initial study of downwash in eVTOL operations. The difference between our current knowledge on downwash, derived mainly from helicopters, and its impact on eVTOLs is the focus of the work. The potential risks and mitigations that result from any difference between helicopters and eVTOLs are presented, with a focus on the safety of passengers and personnel on the ground.
“As noted in the main contractor report (CAP 2576A) the computational technique used has some limitations, such as its treatment of viscosity, the use of ‘perfect’ digital ground surfaces and the lack of wind. While these can be accounted and adjusted for by analysis they would need to be re-visited in light of any subsequent real-world verification and validation (V&V) testing that happens at full-scale.
“The modelling in this work also has only a limited number of dynamic cases and vehicle orientations. As it is already clear that dynamic manoeuvres can significantly affect the downwash and outwash patterns it seems sensible to seek to expand on these at the earliest opportunity. It is especially recommended that this be undertaken in advance of any full-scale V&V work. Wider engagement with manufacturers and potential operators of eVTOLs, and national aviation authorities, around the findings in CAP 2576A would benefit the work by opening its findings to challenge and identifying overlaps with other work that has been carried out globally.
“A better understanding of limits and potential uses of a range of current computational methods for eVTOL design, testing and certification could help provide a clearer view of practical timelines for their safe use. This may be configuration-dependent. An assessment of the effect of outwash velocities and the depth of outwash ground sheets and other phenomena revealed by this research on ground handling personnel, passengers on the ground, luggage and other items, ground equipment etc. would provide a better basis for understanding the overall impact of eVTOL downwash and outwash on safety.”
For more information
https://publicapps.caa.co.uk/modalapplication.aspx?appid=11&mode=detail&id=12377
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