47-33-05 BEECH: (Was Service Note 3 of AD-75777-2 and Service Note 1 of AD-765-1.) Applies to AT-11, C18S and D18S Aircraft.
C18S and AT-11 Airplanes: Inspection required prior to certification or, if certificated, on next periodic inspection but not later than November 1, 1947, and each 100 hours of operation thereafter.
D18S Airplanes (Serial Numbers prior to A-378): Inspection required each 25 hours of normal operation or each 10 hours where the airplane is flown for pilot's transition or instrument training.
Inspect the horizontal stabilizer front spar and subspar for cracks at the points of attachment to the fuselage. At each annual inspection remove stabilizer and the stabilizer lower front skin panel and check for evidence of cracks. If cracks are found the center section of the main spar must be revised or replaced with one having the lower flange-web radius cutout approximately 2 inches from either end. Two 0.064-inch dural channels (404-186053) should be installed between the new attachment fittings (437-186095 and 6) and the main spar web. At the main attachment fittings and 0.032-inch dural doubler (404-186052) should be riveted to the lower skin, the main spar, and the center nose rib flanges.
The forward part of the upper flanges of each stabilizer-fuselage attaching angle should be cut off as far back as the sixth screw hole. The corresponding 12 holes in the stabilizer should be plugged. A three-screw outboard section of the gang nut on each side of the stabilizer subspar should be removed and the corresponding holes in the No. 13 bulkhead angle plugged. The revision of the stabilizer attachments eliminates the necessity for further inspection for cracks except as made during the normal periodic inspection.
(Beech Service Bulletin No. D-18-48 revised April 1, 1948, covers this same subject.)