Pitch-up characteristics for HSCT class planforms - Survey and estimation

Abstract

Low aspect ratio, highly-swept cranked delta and arrow wing planforms are often proposed for high-speed civil transports. These wing planforms offer low supersonic drag without suffering greatly from low liftldrag ratios in low-speed flight. They can, however, suffer from pitch-up at modest angles of attack (as low as 5' angle of attack) during low-speed flight due to leading edge vortex influence, flow separation and vortex breakdown. This paper describes an investigation conducted to study past research on the longitudinal aerodynamic characteristics of highlyswept cranked wing planforms and a new method to estimate pitch-up. The survey of past research placed emphasis on 1) understanding the problem of pitch-up, and 2) ascertaining the effects of leading and trailing edge flaps. The estimation method uses a vortex lattice method to calculate the inviscid flow solution. Then, the results are adjusted to account for flow separation on the outboard wing section by imposing a limit on the equivalent 2-D sectional lift coefficient. The method offers a means of making low cost estimates of the non-linear pitching moment characteristics of slender, cranked arrow wing configurations. Numerous comparisons with data are included.