Wing Twist Measurements at the National Transonic Facility

A technique for measuring wing twist currently in use at the National Transonic Facility is described. The technique is based upon a single camera photogrammetric determination of two dimensional coordinates with a fixed (and known) third dimensional coordinate. The wing twist is found from a conformal transformation between wind-on and wind-off 2-D coordinates in the plane of rotation. The advantages and limitations of the technique as well as the rationale for selection of this particular technique are discussed. Examples are presented to illustrate run-to-run and test-to-test repeatability of the technique in air mode. Examples of wing twist in cryogenic nitrogen mode are also presented.