| A PC based computer model written in BASIC was developed to simulate dry material distribution patterns from agricultural aircraft. Two typical aircraft systems were modeled using several different inputs to compare the predictions to actual data taken from several years of aircraft evaluations. The inputs were designed to be those commonly evaluated by aircraft operators to change depositions uniformity. These include: aircraft speed and altitude, spreader vane intake and exit areas and exit vane angles, material properties, material flow rate, and wind-speed and direction.;Five years of aircraft evaluation data were statistically analyzed to determine the variables which have the most effect on pattern swath widths and uniformity. This field data were generated from computer records of a dry material distribution analysis program. This program determines a recommended swath and pattern uniformity (Coefficient of Variation) based on measured variables. Wind-speed, cross-wind, aircraft speed, altitude and material flow rate affected the recommended swath. Wind-speed, aircraft type, and material flow rate affected the pattern uniformity. As these values increased, swath width, and uniformity decreased with the exception of altitude. As altitude increased, swath width increased slightly.;Air velocity through several spreaders was measured to obtain a better understanding of the initial energy being imparted to particles as they are transported through individual vanes. Dramatic air speed differences were noted in individual vanes on spreaders and differences were noted between aircraft and spreader types. These data were used as a guide to estimate initial particle velocities in the systems modeled.;Several samples of urea fertilizer were taken during the five years of field work. These samples were analyzed to determine average particle mass, terminal velocity, and percentage of material in individual size classes. Very small differences of particle mass and terminal velocity were noted within a size class. Average particle mass and terminal velocity were used as inputs for the simulations in this study.;Good correlations were observed for values obtained from model and field data. Model predicted swath widths, pattern shapes, and responses to aircraft speed and height, wind-speed and direction, and altitude should prove very useful to agricultural aviators when trying to determine how to adjust equipment and operating criteria for a particular situation. |
