Identification of Design-Constraining Flight Conditions for Conceptual Sizing of Aircraft Control Effectors

The stability and control characteristics of any flight vehicle have to comply with designand certification requirements throughout the flight envelope. Starting with the early conceptual design phase, the control effectors are responsible to ensure a flyable and safe vehicle despite their adverse effect on flight performance. The design has to guarantee satisfactory flight characteristics, which will be confirmed or censured during the flight test phase at the end of the design chain. The obstacle at the heart of this undesirable situation is the significant information requirement (in both quantity and quality) of designrelated stability and control analysis during the conceptual phase. Clearly, there is a strong incentive to establish a competent link between the first (initial sizing) and the final (flight test) vehicle development stage during the conceptual design phase to reduce design risks. The objective of the present investigation is to identify a generic set of design-constraining flight conditions (DCFC) for conceptual sizing of the longitudinal, lateral, and directional control effectors of conventional and unconventional fixed-wing aircraft types. The study emphasizes on the identification of design-relevant flight conditions for symmetric and asymmetric type of aircraft in symmetric and asymmetric flight conditions. Since this approach avoids the need to evaluate the entire flight envelope for the flight vehicle under consideration, it becomes, however, more important to identify likely worst-case flight conditions beforehand for sizing of control effectors. As a result, a generic set of DCFC has been defined with the support of a dedicated aerospace knowledge-based system, utilizing A340 and Concorde flight test schedules, taking JAR/FAR 25, MIL Specs, and Concorde’s TSS requirements into account. The paper demonstrates that the design criticality of flight conditions depends, to a large degree, on the aircraft configuration choice.