Replacing the Learjet horizontal stabilizer attach bolt bushings

Effectivity: Learjet 40/45/70/75 aircraft 

ATA: ​55 - Stabilizers​ 

By: TJ Will  – Customer Support Engineering

The horizontal stabilizer on Learjet 40/45/70/75 aircraft is structurally attached at the pivot fittings on the vertical stabilizer. The connection consists of bushings in both pivot fittings, bushings in the horizontal stabilizer hinge fittings, and a primary/secondary bolt configuration through all parts.  

During inspection, the liner of the bushings in the pivot fittings may be found loose and migrating. Replacement of these bushings requires removal of the horizontal stabilizer, which can result in extended downtime.  

Optional Service Bulletins SB40-55-08, 45-55-21, 70-55-01, and 75-55-01 were 

released on Jan. 9, 2023. These service bulletins provide instructions to replace the existing PFTE-lined bushings in the vertical stabilizer pivot fittings with Karon-lined bushings. This material is used in the upgraded flap nose rollers with great success.  

The service bulletin allows nominal, first oversize, and second oversize bushings, based on the final bore size of the fitting. Both bushings must be replaced and mixed bushing types are not approved. In addition, a new primary bolt with a finer surface finish is required.  

Specialized tooling kits that include all necessary reamers and hardware are required for this bushing installation. It is recommended that replacement be accomplished when the horizontal stabilizer is removed for maintenance, to minimize cost and downtime.  

For additional information, please contact your regional Field Service Representative.