AD 49-40-01

49-40-01 LUSCOMBE: Applies to All Model 11A Aircraft.

Compliance required on or before the next periodic inspection but not later than December 1, 1949.

To preclude the possibility of the elevator trim tab actuating horn becoming disconnected from the trim tab, with consequent serious vibration of the horizontal tail surfaces, it is necessary to rework the attachment of the trim tab horn by adding more rigidity to the attachment.

This rework can be accomplished by fabricating two blocks from solid 24ST aluminum alloy that will fit inside the inboard end of the trim tab, one located at the extreme inboard end to which the steel trim tab horn attaches and other one located diagonally chordwise inside the trim tab, with the forward end located approximately 2 1/2 inches and the aft end approximately 1 inch from the inboard end of the trim tab. These blocks, which actually are equivalent to solid ribs, should be approximately 3/8-inch wide and shaped in elevation to fit the inside contour of the trim tab. The attachment of these ribs should be effected by four AN 456AD4 rivets in each, drilled on assembly, with the rivets driven through both upper and bottom skins of the trim tab. The trim tab horn should be attached to the trim tab through their regular attaching holes, riveting the horn with two AN 456AD4 rivets to the chordwise end of the inboard revised solid rib and the two remaining holes as originally attached with two AN 456AD4 rivets. The aluminum alloy blocks or ribs should be finished with a protective coating of zinc chromate prior to assembly of the trim tab. An equivalent modification to that described above and in Luscombe Service Bulletin is acceptable.

(Luscombe Service Bulletin No. 1-1149, dated January 25, 1949, covers this same subject.)