Replacement of forward engine mount firewall screws

Effectivity: Learjet 40/45/70/75 aircraft

ATA Code: ​54 - Nacelles/Pylons​

By:  Tj Will – Field Support Engineering 

Bombardier would like to make operators aware of a recent service bulletin regarding forward engine mount firewall seal fasteners. 

The recommended Service Bulletin 45-54-5, released in October 2005, focused on gouging of the forward engine mount from screws that attach to the forward engine mount firewall seal. The offending fasteners were removed, and a clamp (angle) was added to hold the seal in place to accommodate the removal of the fastener. This service bulletin was effective for aircraft 45-005 through 45-231. A production change at 45-232 added dimpled washers and countersunk screws at these two locations; however, in some cases, the fasteners can still cause damage to the forward engine mount.   

Service Bulletin 45-54-5 was revised and extended theeffectivity to capture all Learjet 45 aircraft serial numbers; recommended service bulletins 40-54-05, 70-54-02, and 75-54-01 were created. All four bulletins were released on October 6, 2025, and provide the instructions found in the original service bulletin release.      

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