Learjet lower wing skin corrosion inspection

 Effectivity: Learjet 40/45/70/75 

ATA Code: ​57 - Wings​ 

By:  Tj Will – Field Support Engineering 

Bombardier would like to make operators aware of a recent Service Bulletin regarding inspection of the lower wing skin on Learjet 40/45/70/75 aircraft. Corrosion has been found on the lower wing skin at the forward and aft drain valves.   

Recommended Service Bulletins 40-57-09, 45-57-16, 70-57-06, and 75-57-05 were released on March 31, 2025.  These service bulletins provide instructions to eddy current inspect the lower wing skin externally around the drain valves as well as the bore after drain valve removal.  Time of compliance varies slightly between the bulletins. For bulletins 45-005 through 45-200, the time of compliance is 12 months after release. The remaining aircraft and respective Service Bulletins are 24- month time of compliance after release.   

Temporary Revision No. 57-06 to the Learjet 40 series NDI (Nondestructive Inspection) Manual was released to add the forward drain valve locations to the existing eddy current inspection of the wing skin (Part 6, 57-30-02). Temporary Revision No. 57-07 was also released and adds a new eddy current inspection procedure to inspect the bore at each drain valve (Part 6, 57-30-03).    

Learjet 40/45/70/75 Aircraft Maintenance Manuals will be revised to incorporate a six-year (72 month) recurring inspection of the skin and bore at the drain valves. Additionally, an eddy current inspection of the forward drain valve openings is being added at the same interval as the aft holes (10,000 hour initial/5,000 repeat).   

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