Measurements of the direct hinge-moment derivatives at subsonic and transonic speeds have been made for a cropped delta wing of aspect ratio 1.8 with an oscillating full-span flap. The measurements were obtained with new derivative apparatus fitted to the National Physical Laboratory 9½-in. High Speed Tunnel, and some account is given of the estimation of apparatus errors.nThe effect of amplitude of oscillation ξ0 and frequency parameter ω on the derivatives has been investigated;a maximum value for ω of 0.25 at M = 1.0 being attained.nA comparison of the measured derivatives with theory shows satisfactory agreement for the damping and reasonable agreement for the stiffness at subsonic speeds. At supersonic speeds (M =1.1) large discrepancies occur.
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