Designer's Notebook

Columnist Barnaby Wainfan discusses the factors that affect the longitudinal stability of an aircraft during a variety of maneuvers. Designers make compromises to keep stick forces down so that a pilot can control an airplane, but sometimes they go too far, and light control forces can result in problems that are just as serious as those posed by forces that are too heavy. Whats a designer to do? The most important considerations are presented.

The perils of PIO;

Its an age-old duality: stability versus maneuverability. Many factors go into developing and building any aircraft, and the designers choices will affect a pilots workload, for good or ill. Among the topics discussed are trim, pitch stability and yaw stability;

The author explains how the characteristics of an airplane affect pilot ability to complete tasks, response factors, stability and damping of the airframe to changes in angle of attack, basic stability, trim, control forces, and control power. He also addresses the controversy behind the design of airplanes, their characteristics and the resultant suitability for various types of flying;

The author discusses the theory and effect of constant-speed propellers on piston-engine airplane performance, and compares fixed-pitch versus constant-speed props, effect on thrust HP and propulsion, the comprises involved in choosing a prop, how props perform in various conditions and phases of flight, how variable-pitch props work, and why a constant-speed prop is the best choice for high-performance aircraft.