Wind-tunnel measurements of yawing moment due to yawing (nr) on a 1/5.5 scale model of the meteor Mark F.III

Abstract

During recent investigations into the self-excited oscillations ill yaw, experienced on Meteor aircraft, the lateral stability derivative, nr, was measured in flight, and found to differ considerably during initial experiments from the theoretical estimate. A new technique was therefore devised to measure nr in the wind-tnnnel; and, with its aid, modifications were tested on a model with the object of reducing the self-excited oscillations in flight. Measurements of nr were made over a range of Reynolds numbers, and for different periods of oscillation of the model. The final comparison of the flight and wind-tunnel tests, after certain refinements in technique of the former, and after corrections for solid friction to the latter had been made, showed that the full-scale measurement of nr was about 10 per cent less than-that obtained in the tunnel. Considering the difficulties involved, this agreement may be considered as satisfactory. For the model in the standard condition, the value of nr was about 20 per cent less than the estimated figure of -0.108 at zero lift, but with dorsal fins (see sections 5.7 and 5.8). It was found possible, without altering the value of nv to increase the value of nr to the estimated value. The 'snaking' tendencies of the model, which were more pronounced at small angles of incidence, could be greatly reduced by fitting an upper dorsal fin (described in section 5.7).