Flight Mechanics of the Wright Aircraft 1903-1912

Perhaps the most curious aspect of the Wright Brothers' program to invent and commercialize the airplane is their decision in 1900 to use their novel canard configuration, and to persist with that geometry until 1910 despite the known deficiency that the aircraft were unstable in pitch. The reasons for their initial choice are well-known. Several studies in the part twenty years have proven beyond doubt that the Wrights did not intentionally make their canards unstable. The pitch instability of their machine was an unwitting byproduct of their design chosen partly out of fear of the conventional design and partly (they reasoned) for more positive control. With their great emphasis on control, the Wrights were able to develop a successful aircraft, albeit difficult to fly additionally because the 1903 aircraft also possessed a fast spiral instability. A canard design is not necessarily unstable, but owing chiefly to their airfoil, and an unfortunate fore-and-aft mass distribution, the Wright canards were all unstable. Though easier to fly, their 1909 aircraft was more unstable than the famous 1903 FZper and the Brothers did not have a stable design until they finally adopted a conventional aft horizontal tail in 1910. Successful control of the canard aircraft depended heavily on large damping-in-pitch. The purpose of this paper is to apply modern analysis of flight mechanics to trace the detailed flying characteristics of their powered aircraft from 1903 to 1910 when they finally gave up the canard. Its a story in which technology, stubborness and commercialization are intimately mingled; we are concerned here only with the technology. © by 2003

Effects of Displayed Error Scaling in Compensatory Roll-Axis Tracking Tasks

This paper describes an investigation into the effects of displayed error scaling on manual control behavior during compensatory roll-axis tracking. Previous experiments have indicated that for compensatory displays that, similar to an artificial horizon, present the roll tracking errors in rotational form, the deviations for typical quasi-random forcing function signals are comparatively small and difficult to perceive. This was found to lead to degraded tracking performance and lower crossover frequencies than would be expected. To investigate this, a roll-axis tracking experiment has been performed in which the scaling of the presented tracking errors was varied from 0.5 to 5 times the true tracking error. In addition, both double integrator dynamics and typical conventional roll dynamics of a small jet aircraft were considered in a mixed experimental design. The main hypothesis for this experiment was that increased scaling of the presented roll-axis tracking error would result in improved tracking performance and correlation of manual control inputs with the target forcing function signal. In addition, these effects were hypothesized to be more pronounced for the more difficult double integrator dynamics. For both controlled elements, both tracking performance and linearity of pilot control were indeed found to increase with increasing display gain, leveling of for the highest considered display gains. Further analysis of manual control behavior using McRuer et al.’s Precision Model revealed marked changes in the adopted control strategy due to changes in displayed error scaling, which were found to be highly similar for both controlled elements.Control & OperationsAerospace Engineerin

Modeling Human Dynamics in Combined Ramp-Following and Disturbance-Rejection Tasks

This paper investigates the modeling of humanmanual control behavior for pursuit tracking tasks in which target forcing functions consisting of multiple ramp-like changes in target attitude are used. Due to the use of a pursuit display and the predictability of such forcing function signals, it can be anticipated that a pursuit or precognitive control strategy, consisting of open-loop feedforward control inputs in response to the predictable reference signal, is applied by the human operator. If combined with an additional disturbance on the controlled element, a control task results that is similar to performing a commanded turn entry/exit or altitude capture in turbulence. It is as of yet uncertain if such pursuit or precognitive control is indeed used during such a control task, and to what extent a quasi-random disturbance would suppress pursuit/precognitive control strategies. A human-in-the-loop evaluation of the combined ramp-following and disturbance-rejection task was performed to gather data for the modeling of human manual control behavior. It is found that despite the anticipated pursuit and precognitive control inputs, classical compensatory models of human manual control dynamics are highly capable of describing human dynamics for these specific control tasks. Measured control inputs, however, are found to correspond well with proposed models for open-loop feedforward operations as well, suggesting future evaluation of a model of human behavior that combines, or switches between, error-reducing compensatory and open-loop feedforward operations.Control & OperationsAerospace Engineerin

Effects of Heave Washout Filtering on Motion Fidelity and Pilot Control Behavior for a Large Commercial Airliner

Due to the significant translational heave motion at the pilot station associated with changes in aircraft pitch attitude, themotion cueing for aircraft pitchmaneuvering typically requires significant heave washout filtering. Previous studies that attempted to motivate choices in the motion cueing strategy for pitch maneuvering based on measurements of pilot behavior. For the small conventional aircraft considered in these studies, the results indicated that, despite the fact that pilots were found to adapt their control strategy to changes in heave cueing, the pitch rotation had a dominant influence on pilot behavior during pitch tracking. For large commercial airliners, a relevant application of this research as a lot of commercial pilot training occurs on moving-base simulators, the location of the pilot station is significantly further from the center of aircraft pitch rotation, yielding more pronounced heave motion cues during changes in pitch attitude. This difference, in addition to typically slower pitch dynamics that require more lead equalization, implies the best choice in motion cueing for large aircraft may be significantly different from what would be optimal for smaller aircraft. In this paper, an experiment is described in which pilot behavior is measured in a pitch attitude disturbance-rejection task with a controlled element and motion cueing conditions that are representative for a Boeing 747 aircraft. Different third-order heave washout filter settings were considered, in addition to a variation in the presence of 1-to-1 rotational pitch motion. Significant effects of the applied variation in pitch and heave motion cueing are observed, even though the effect of heave motion feedback is indeed found to be comparatively more important for larger aircraft. Furthermore, a heave motion filter that combined a low gain with low filter phase distortion was found to yield the least effect on pilot behavior, while for heave motion filters with a relatively high gain and high break frequency significantly larger contributions of motion feedback to pilot behavior were observed.Control & OperationsAerospace Engineerin