What was found
AFTER TAKE OFF, TOWER REPORTED LT ENGINE TRAILING VISIBLE BLACK SMOKE, ALL COCKPIT INDICATIONS NORMAL. F/A REPORTED STRONG BURNING ELECTRICAL ODOR TOWARDS REAR OF CABIN. AIR RETURN, PERFORMED AMM TASK 05-51-58-910-801C1, CHECKED SATISFACTORY. MX TEST FLIGHT PERFORMED. INITIAL OIL/FUEL ODOR NOTED DURING TAXIOUT. ODOR DISSIPATED AFTER TAKE OFF IAW FIM 71-R-05-828 SATISFACTORY. TROUBLESHOT FURTHER IN FLIGHT WITH BLEED SOURCE OF ENG AND APU. NO FURTHER ODOR FOR TEST FLIGHT DURATION OF 1 HR, 16 MI.