Application of the CATNLF Design Method to a Transonic Transport Empennage Using CDISC

A novel Crossflow Attenuated Natural Laminar Flow (CATNLF) design method has been
developed to achieve laminar flow on aircraft empennage at transonic flight conditions. This
approach has been applied to the design of a nonlifting vertical tail using CDISC, a knowledgebased aerodynamic design tool developed at the NASA Langley Research Center. A horizontal
tail was also designed using an enhanced CATNLF design approach for low-lift components.
CDISC was coupled with USM3D-ME, a Navier-Stokes computational fluid dynamics solver.
Stability and transition software was used to determine the laminar extent on the surfaces.
Results indicate laminar flow can be sustained at midcruise conditions to about x/c=0.40 on
the vertical tail and as much as x/c=0.65 on the horizontal tail lower surface. Transonic
longitudinal off-design analysis indicates minimal change in the laminar extent. However,
nonzero sideslip angles at transonic conditions can cause premature transition relative to the
midcruise condition.