Methods Used in the NACA Tank for the Investigation of the Longitudinal-Stability Characteristics of Models of Flying Boats.

摘要

Recent trends in the design of flying boats, such as high wing loadings (high get-away speeds) and high load coefficients (relatively narrow hulls) have made the problems associated with longitudinal stability of primary importance. The need for additional research on longitudinal stability or porpoising is recognized and the stability characteristics of models of several flying boats have been determined in NACA Tank No. 1. These investigations were made for the purpose of (1) determining suitable methods for evaluating the stability characteristics of models of flying boats, and (2) determining the design parameters which have an important effect on the porpoising. This report is mainly concerned with the construction of suitable, models, the apparatus, and the methods used in the tests. The effect of changes in some design parameters is discussed. The models were dynamically similar to the full-size airplane. Dynamic similarity required the use of a complete model with wings, tail, and hull built to scale dimensions, the weight of the model being so disposed as to result in scale weight, balance, and pitching moment of inertia. The use of such models results in forces and motions similar to those of the full-size flying boat. A description of the construction of a typical model and the ballasting procedure used is presented. (KAR) P. 2.