NACA-TN-2534

Abstract

An investigation was made to determine the low-speed static stability and yawing stability characteristics of a 45° sweptback high-wing, low-horizontalTail configuration with various twin vertical wing fins. In general, the static longitudinal stability characteristics were not affected by either upper-surface or lower-surface wing fins. The results indicated that the directional stability for a high-wing configuration with twin upper-surface or lower-surface vertical fins located at 70 percent of the wing semispan was smaller at low angles of attack than for a similar configuration with only a single vertical tail at the rear of the fuselage. The twin-fin configurations, however, were directionally stable throughout the angle-of-attack range, whereas the single vertical tail configuration was directionally unstable at moderate and high angles of attack. The twin upper-surface fin configuration was found to be more directionally stable at low angles of attack but only 50 percent as effective as the twin lower-surface fin configuration at moderate angles of attack. At high angles of attack, the directional stability for the upper-surface fin configuration decreased as the angle of attack increased. The positive effective dihedral.(at 0° angle of attack) normally associated with a high-wing fuselage configuration was increased by the addition of twin lower-surface wing fins at 70 percent of the wing semispan. As the lower-surface fins were moved outboard, the effective dihedral was reduced. In the case of the upper-surface wing fins, the effective dihedral of the complete configuration was made more positive throughout the angle-of-attack range.