A perspective on superaugmented flight control - Advantages and problems

Superaugmented aircraft are an important subclass of actively controlled, highly augmented aircraft. The aircraft without augmentation is unstable; the control system not only redresses the stability and control imbalance, but also provides effective vehicle dynamics that differ in kind from those associated with conventional aircraft. In this paper, the longitudinal properties of highly unstable aircraft and typical superaugmented control systems used to remedy their dynamic deficiencies are explored generically. The topics considered include: (1) Basic flight control system architectures suitable to reduce or completely alleviate the unstable aircraft characteristics. (2) The primary dynamic characteristics and regulatory properties of typical superaugmented aircraft control systems, including governing factors in the linear system, dominant mode characteristics, and fundamental stability margin properties. The total available gain range factor is presented as a basic measure that relates degree of instability, control system limitations, and key control system adjustments. (3) Some flying qualities features for superaugmented aircraft with rate command/attitude hold, extended bandwidth, and attitude command configurations.