81-14-10 NORTH AMERICAN: Amendment 39-4159. Applies to all AT-6D 81-14-10 (SNJ-5), AT-6F (SNJ-6), SNJ-7, and T-6G aircraft equipped with single piece design horizontal stabilizer rear spar connector fittings (P/N 77-21021, 4 fittings per spar). This AD does not apply to those aircraft equipped with two piece design connector fittings (P/Ns 77-21021-3 and 77-21021-4, 8 fittings per spar). \n\nAccomplish the following: \na)\tWithin 20 flight hours after the effective date of this AD and every 20 flight hours thereafter until b) is accomplished: \n1.\tRemove the fuselage to vertical stabilizer fairing assembly and the rear fairing assemblies at the horizontal stabilizer. \n2.\tVisually check the spar connector fittings for cracks. If cracks are found, fitting must be replaced with an airworthy part before further flight. \n\nb)\tAt next annual inspection: \n1.\tRemove the fuselage to vertical stabilizer fairing assembly and the rear fairing assemblies at the horizontal stabilizer. \n2.\tRemove the 1/4-inch bolts which attach the upper and lower spar connection fittings (P/N 77-21021) of the rear spar assembly. \n3.\tRemove the 4 connection fittings from the spar, remove paint from the connection fittings, and check for cracks using standard dye penetrant inspection methods. Replace any cracked fittings with serviceable ones and repaint all others. (See note.) \n4.\tInspect for fit between the connection fittings and the spar with a feeler gage prior to installation of the bolts. If gaps greater than 0.010 inches exist, shims are necessary. \n5.\tFabricate aluminum shims 3-1/8 inches x 15/16 inch and of necessary thickness, and place on either side of spar flanges, maintaining a parallel overall dimension to fit inside the connection fitting with a maximum clearance of 0.010 inches. \n6.\tDrill holes through the shims to match those in the fitting. Remove all chips and reinstall the various parts, including fairings. \n\nNOTE: One source of replacement fittings is Banaire Enterprises, 962 E. Lincoln St., Banning, California 92220 (Tel. (714) 849-8323). \n\nThis amendment becomes effective July 13, 1981.