What was found
JUST AFTER TAKEOFF DURING INITIAL CLIMB, CREW NOTICED BLUE SMOKE IN COCKPIT COMING FROM LEFT SIDE. CREW DONNED MASKS/GOGGLES AND STARTED IMMEDIATE RETURN TO AIRPORT, AFTER POWER REDUCED SMOKE STOPPED. CHECKLIST FOLLOWED, UNSCHEDULED LANDING PERFORMED AND LANDED WITHOUT INCIDENT. MAINTENANCE EVALUATION FOUND EVIDENCE OF APU LEAKING COMPRESSOR SEAL AS EVIDENCED BY THE OIL/SOOT/COKING ON THE COMPRESSOR BLADES. APU PLACED ON MEL AND SCHEDULED FOR COMPRESSOR CARBON SEAL REPLACEMENT. MAINTENANCE ALSO REPLACED COALESCER SOCKS AND PERFORMED ENGINE RUNS WITH ACM’S WITHOUT ANY ISSUES.