Descriptions about dynamic wind tunnel tests, using a free oscillation technique at low speed, are given together with the obtained results. Two kinds of "in-put" signals are taken. One of them is the "step" signal, and the other is the "random" signal. And data of expriments in the former are analyzed by Fourier integral method, and the ones in the latter by computing the power spectrums of signals. Obtained results show; 1) By a free oscillation technique, which is one of the simplest techiques, we can get the dynamic stability derivatives of the model airplanes; Cmα, Cmq+Cmα, Clp, Cnβ and Cnr-Cnβ, and these are able to simulate the one of the true airplanes. 2) Especially paying attention to the accuracy of the analysis, we can get the derivatives; Clβ, Clr and Cnp, at any rate.
Longitudinal dynamic stability derivatives of firstly a rocket configuration model at Mach nu-mbers from 0.6 to 3.0 and secondly several air-plane configuration models at Mach numbers from 1.5 to 2.25 were measured by the forced-oscilla-tion technique in the transonic and the supersonic wind tunnels at NAL. The static stability deri-vatives measured by dynamic test coincided with those measured by static test. The dynamic sta-bility derivatives, on the other hand, showed themselves being of fairly large values compared with calculated ones. In addition to the test results, some details of the test equipments and the error analysis for the data reduction system are included. It is shown by this error analysis, that as the output of the balance is decomposed by the resolver into the static and the dynamic derivative components, the latter is very much influenced by the former and that the interference factor can be obtained by the data of wind off condition tests. Also presented are the damping derivatives in roll, which are measured by another test rig, and which agree precisely with calculated values.
Free Flight Model FFM-10 is a model which simulates supersonic aircraft with delta wing. The model is propelled by a rocket motor installed in the fuselage. Longitudinal short period motion is excited by two side jets ignited in sequence. Measurements of acceleration in the direction of pitching motion enables to derive longitudinal static and dynamic aerodynamic derivatives. The results are compared with theoretical estimates and shows fairly good agreement. Although much improvement should be pursued to obtain enough accuracy, the preliminary result shows that the technique employed is very promising.