47-14-02\tBOEING: (Was Mandatory Note 3 of AD-719-1 and Mandatory Note 3 of AD-726- 1.) Applies to 307 Series Aircraft. \n\tCompliance required prior to May 15, 1947. \n\tInspect the attachment of the main landing gear motors to the retracting unit. Determine, by testing, that the keys in these locations have been heat treated to 200,000-220,000 pounds per square inch. All keys that do not meet this strength specification should be replaced. Aircraft which have had this attachment revised to include an additional gearbox for the hand retracting drive are not subject to this inspection. \n\t(TWA E.O. No 3489 covers this same subject.)