APU engine removal

Effectivity: Learjet 45/75 aircraft 

ATA Code: ​49 - Airborne Aux Power​ 

By: TJ Will, Field Support Engineering 

Bombardier would like operators to be aware of recent Service Bulletins  regarding operating Learjet 45/75 aircraft that have the APU engine removed for maintenance or repair.   

Optional Service Bulletins 45-49-18 and 75-49-03, Auxiliary Power Unit (APU) Engine Removal and Reinstallation, were released on March 31, 2025.   

These Service Bulletins provide instructions to temporarily remove the APU engine for scheduled maintenance/overhaul or repair and reconfigure the aircraft for flight. All removed components are weighed and total weight is recorded. Plugs and caps are added to fuel and drain lines, cover plates are installed at exhaust and cooling ducts, and electrical connectors are bagged and stowed.  

All Service Bulletin installed plates/hardware are weighed prior to installation and total weight is recorded. Final weight and balance is then calculated using the total recorded  weights.   

Upon receipt of the APU engine, the Service Bulletin provides instructions to remove the Service Bulletin components, reinstall the APU engine, and return the aircraft to its original configuration. Final weight and balance is calculated in the same manner. 

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