74-18-10 BOEING: Amendment 39-1945. Applies to all model 707/720 series airplanes, certificated in all categories. \n\n\tCompliance required as indicated. \n\tTo prevent potential oscillatory longitudinal flight on Boeing models 707/720 series airplanes, accomplish the following: \n\tBy September 1, 1976, unless already accomplished, inspect and adjust the contour mismatch of the upper surfaces between the horizontal stabilizer and elevator in accordance with Boeing Service Bulletin No. 3151, or later FAA approved revisions or in a manner approved by the Chief, Engineering and Manufacturing Branch, FAA Northwest Region. \n\n\tThis amendment becomes effective thirty (30) days after publication in the Federal Register.