80-26-51: Control System Jamming

80-26-51 BOEING: Amendment 39-4072. Applies to Boeing Model 737 series airplanes, certificated in all categories, prior to line number 726. To prevent control system jamming, accomplish the following within the next 150 hours time-in-service after the effective date unless already accomplished, or unless the affected bolt assemblies have been removed and reinstalled since manufacture. \n\n\t1.\tInspect the bolt assemblies installed at the upper and lower clevis of each elevator power control unit input rod assembly for proper installation in accordance with Boeing Alert Service Bulletin 27A1109, dated December 11, 1980, or later FAA-approved revisions. Bolt assemblies not properly installed must be reinstalled in accordance with the service bulletin.\n \n\t2.\tAlternate methods of compliance with this Airworthiness Directive may be used when they are approved by the Chief, Seattle Area Aircraft Certification Office, FAA Northwest Region. \n\n\tThis amendment becomes effective April 1, 1981, and was effective earlier to those recipients of telegraphic AD T80-26-51, dated December 13, 1980.