Airworthiness Directives (ADs) Issued

AD 64-10-02, Effective June 5, 1964, required replacement of Horizontal stabilizer trim limit switches on 707/720 series in accordance with Boeing Service Bulletin 1635 (R-1). The limit switches were originally installed to prevent the stabilizer jack screw from striking the mechanical stops. The Service Bulletin relocated the switches to limit the amount of electric trim available AD 65-13-01 Effective July 15, 1965, required several actions including further restrictions in the stabilizer trim settings on certain 707 airplane models. It modified horizontal stabilizer electric trim limits on the 707/720 series. Service Bulletins 1699(R-1) and 1990 revised stabilizer trim limits. Service Bulletin 1990 revised nose down trim to 0.6 degrees on specific 707 airplanes to improve controllability in severe turbulence.

A description of the 707/720 stabilizer trim limit revision is contained in an article published by Boeing in the June, 1964 issue of the “Boeing Airliner” magazine. The trim limit revision article may be found at (Boeing Airliner 707/720 trim limit revision article, June, 1964).

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