What was found
WHILE POWERING UP TO TAKE RUNWAY FOR TAKEOFF, ANOTHER ACFT OBSERVED SPARKS AND/OR FLAMES COMING FROM NR 1 TAILPIPE. ALL ENGINE INDICATIONS WERE NORMAL WITH NO FIRE INDICATIONS. ACCOMPLISHED ENGINE TAILPIPE FIRE CHECKLIST. NO FURTHER SPARKS OF FLAMES OBSERVED. ACFT GROUNDED. ACCOMPLISHED FOD INSPECTION, IAW AMM 71-00-00-800-802-F00. INTERROGATED AAVM, IAW 77-31-00-970-803-F00. INSPECTED ENGINE FLAME ARRESTOR, IAW AMM 71-00-00-800-F00, STEP 3, F2, A. INSPECTED MAGNETIC CHIP DETECTORS, IAW AMM 79-00-00-200-804-F00. PERFORMED VISUAL AND ODOR CHECK OF OIL TANK FOR POSSIBLE PRESENCE OF JET FUEL, IAW AMM 12-13-11-100-801. EXAMINED PRIMARY EXHAUST NOZZLE AND PLUG FOR PRESENCE OF OIL IAW AMM 71-71-00-200-801-F00. INSPECTED TURBINE REAR FRAME AFT SUMP AREA FOR INDICATIONS OF LEAKS OR HEAVY OIL COKE, IAW AMM 79-00-00-200-806-F01. IN ALL ABOVE INSPECTIONS, NO DEFECTS NOTED. PRECAUTIONARILY REPLACED NR 1 ENGINE SCAVENGE FILTER IAW AMM 79-21-06. INSTALLATION TESTED GOOD. NO LEAKS NOTED. ACCOMPLISHED POWER ASSURANCE TEST, TEST 5, IAW AMM 71-00-00-700-813-F00. COMPLETED ALL STEPS OF TSR, NO DEFECTS NOTED, ENGINE PARAMETERS WITHIN LIMITS.