Twin Commander Aircraft has developed several new kits that improve evacuation of moisture under the fuselage-to-vertical-stabilizer dorsal fin on Twin Commanders.
Custom Kit (CK) 193 (for models 690A and B) and CK 198 (for models 690C/D, 695, and 695A) are comprised of a weep-hole system of parts, including shims, to be installed under the existing dorsal fin to provide channels for moisture to drain out of the cavity beneath the fin. Allowing the moisture to drain prevents the onset of corrosion beneath the dorsal fin, company officials explain.
As an option, the original plastic dorsal fin can be replaced with one made from composite laminate material. The new dorsal fin also incorporates channels to disperse moisture.
CK 195 is the new dorsal fin for Twin Commander models 500S, 681, 685 and 690; CK 196 is for the 690A and B.