57-26-02 VICKERS: Applies to All Viscount 700 Series Aircraft.
Compliance required not later than July 1, 1958.
To preclude the possibility of the flap idler sprocket retaining nut, P/N 60903-39 and 60903-1151 from becoming unscrewed, the improved locking means for the sprocket shaft nuts at Nos. 1, 2, and 3 flap units should be incorporated. This consists of the installation of a screwed collar P/N 70103-4227 and a split pin, P/N SP9E10. Vickers PTL No. 174 and Modification Bulletin No. 2439 cover the same subject. Modification No. 2439 has been classified as essential by the British Air Registration Board. The FAA concurs and considers compliance mandatory.