Stability of Semimonocoque Wing Structures

Abstract

The Consolidated Vultee Aircraft Corporation recently built and tested several cambered box beams that were structural models of stressed-skin airplane wings. I t was found, as a result of these tests, tha t plate-stringer column-fixity factors of the specimens ranged from 1.00 to 3.00. These observations are rather revealing in view of the frequent arguments among stress analysts concerning the correct fixity factor to be used for calculating allowable plate-stringer loads. I t is therefore especially satisfying to find tha t the test data are in harmony with a simple approximate theory of elastic stability of wing structures. This theory exposes the possibility of occasionally exerting control over fixity factors for purposes of weight economy or bulkhead rearrangement. I t further suggests modifications of wing construction, such as the substitution of shallow ribs for bulkheads in highly cambered wings.