Designer's Notebook

The diagnosis of pitch sensitivity problems boils down to one of two things: too little static margin or control system problems. This month we discuss how to modify the airplane to fix them;

This month we use the accumulated flight-test data to determine what exactly is causing the unacceptable flying qualities of the airplane so that the best way to fix the problem can be identified;

Flight testing for longitudinal stability problems continues this month as columnist Barnaby Wainfan details tests for stick force as related to trim and stick-free stability of an aircraft. The object is to gather data and analyze it to see if the hypotheses about the nature of the problem hold up under scrutiny.

Columnist Barnaby Wainfan continues his flight-testing discussion by taking up the topic of longitudinal stability. By identifying the origin of the problem, whether it be a control-system issue, a too-small static margin, or a combination of the two, the flight tests he recommends will help to isolate the issue.

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.