Quantification of an atypical air environment in support of uncrewed aircraft operations over congested areas

Abstract This paper demonstrates a method for quantifying the unmitigated mid-air collision (MAC) rate ( ${\lambda _{{\textrm{MAC}}}}$ ) between crewed aircraft and uncrewed aircraft (UA) above different congested area operating environments, to support broadening the definition of an atypical air environment (AAE) within the United Kingdom (UK). The underlying principle of this work is that all crewed aircraft should be operating in accordance with UK Standardised European Rules of the Air (SERA), which dictate minimum operating heights over built-up areas, specifically 1,000 ft in the majority of cases, except during take-off and landing. It is unrealistic, however, to assume that this rule is never breached; therefore, we present a method for objectively evaluating the likely encounter rate. We systematically consider the exclusion of runway protection zones (RPZs), aerodrome traffic zones (ATZs) and helicopter landing sites (HLSs) from the operating areas and evaluate the effect on ${\lambda _{{\textrm{MAC}}}}$ . Results are presented that apply the methodology to over 33,000 hours worth of air traffic data recorded at three different sites across the UK. It is concluded that the operation of UA overhead congested areas, outside of RPZs and HLSs, likely satisfies an appropriate target level of safety (TLS) to be considered an AAE up to a height of 100 m above ground level (AGL) both inside and outside of controlled airspace.