NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS LANGLEY FIELD VA LANGLEY AERONAUTICAL LABORATORY
An investigation was made in the Langley 300 MPH 7- by 10-foot tunnel to determine at low speed the longitudinal stability characteristics of a 60 deg swept-back, tapered, low-drag wing of aspect ratio 2.55. Several modifications were made to this wing in an attempt to improve its longitudinal stability characteristics. The results show undesirably large changes in the longitudinal stability characteristics of the 60 deg swept-back wing. The most effective modification consisted in an alteration to the plan form of the wing by extending the leading edge forward about half a chord length over the outer 25 percent of the span. The maximum lift coefficient of the swept-back wing was about the same as that of the unswept wing, but the angle of attack for maximum lift of the swept wing was more than twice that of the straight wing. Decreasing the aspect ratio from 2.55 to 1 improved the longitudinal stability characteristics of the wing, particularly in the range of high lift coefficient. The results of testing the wing with a deflectable tip showed little promise with regard to improvement of the longitudinal stability characteristics, but deflecting the tip offered interesting possibilities as a means of longitudinal and lateral control.