Unrestrained Aeroelastic Divergence in a Dynamic Stability Analysis

Abstract

Comparison of Model Predictions with Field Data On July 13 (Friday), 1979, Cleveland center recorded the number of actively controlled aircraft as a function of time of day. (This recording also included a small number of controlled non-IFR aircraft.) Cleveland center, which controls the airspace over parts of Ohio, Michigan, New York, Pennsylvania, and West Virginia, is one of the busiest centers. The sum of the models' predicted counts of scheduled and unscheduled aircraft was compared with the recorded counts for the above data for the times, 8 a.m.-6 p.m., on the hour. At the time the comparisons were made, unscheduled aircounts could be predicted for any day in April 1978. Therefore seasonal adjustment factors for GA activity based on historical data were applied to these counts, so that they would be representative of counts on a typical Friday in July 1979. Figure 1 shows predicted IFR counts and actual counts over Cleveland center. (Data points are connected by lines as a visual aid.) Similar comparisons were made for Houston, Kansas City, and New York centers (one day for each center in the summer of 1979, although the day of the week was different in each case). All comparisons between predicted and measured aircounts show good agreement in terms of small numerical differences in the amplitudes and also similar harmonic content. The largest difference occurs at the peaks and is about 10%. This agreement is sufficient for system planning purposes. It is planned to extend these comparisons to other centers for additional days and seasons of the year, and to quantify the (statistical) differences between measured and predicted counts.