On the Mechanics of Transition Produced by Particles Passing Through an Initially Laminar Boundary Layer and the Estimated Effect on the LFC Performance of the X-21 Aircraft

Numerous flight tests of the X-21 aircraft have shown total loss of LFC while flying within, or in the proximity of, visible clouds. In addition, erratic LFC performance has been observed in conditions of light haze when the humidity of the air is relatively high. An investigation of the phenomena which might account for loss of LFC in or near clouds and for the erratic performance in light haze has been conducted. The phenomena considered in the investigation are classified as either thermodynamic effects or mechanical effects. The results derived from the study of thermodynamic and mechanical effects are presented with recommendations for follow-up work.