What was found
ON DESCENT CREW EXPERIENCED STRONG BURNING OIL SMELL IN COCKPIT. LANDING UNEVENTFUL. MAINTENANCE RAN APU BLEED, PACK ONLY, NORMAL POSITION SMELLED OIL IN CABIN. FOUND OIL RESIDUE AT HEAT EXCHANGER HOT AIR REGULATING SHUT OFF VALVE TRIM AIR MOVING FORWARD TO THE CABIN DUCTING IN THE FLOOR. DECISION MADE TO CHANGE OUT APU. THIS INFORMATION HAS BEEN FORWARDED TO LEARJET ENGINEERING THROUGH THE JSLLC CAS REPORTING SYSTEM.