The correlation of longitudinal dynamic response data with theoretical predictions was considered. A satisfactory correlation was obtained with either fairly complete equations of motion or greatly simplified ones. With the proper values of lift, drag, moment, and total derivatives, the equations of motion were considered capable of predicting with satisfactory accuracy the responses observed in flight testing. However, existing theories were generally inadequate for predicting the proper values of the important derivatives. The simplified equations were considered adequate for the slower modes of motion because the errors introduced by the simplifying assumptions were overshadowed by the inaccuracy of estimating the more important derivatives. These equations also predicted with reasonable accuracy frequency-response information derived from test data. The effects of nonstandard bar damper settings were not satisfactorily explained these were assumed to be associated with damper nonlinearities.