What was found
NR 1 ENGINE OIL PRESSURE FLUCTUATES BETWEEN NORMAL & CAUTIONARY RANGES. MASTER WARNING TRIPLE CHIME SOUNDED (3) TIMES. CAUTION PANEL DARK WHEN CHECKED IN RESPONSE TO CHIMES. RETURNED TO DEPARTURE. LANDING UNEVENTFUL. FOUND NR 1 ENG OIL FILLER CAP MISSING. R & R OIL FILTER TUBE AND CHECK BALL ASSY AND REPLACED MISSING OIL CAP. SERVICED NR 1 ENG WITH OIL. CW ENGINE INSP AFTER LOW OIL PRESSURE IAW TASK 05-53-00-210-815. REMOVAL OF STARTER/GEN NOT REQUIRED, GEN COOLING FAN USED TO TORN HP ROTOR. NO OIL CONTAMINATION OR CHIP DETECTION NOTED. MAIN OIL PRESSURE DECREASED TO 44 PSID TO 01 PSID FOR A TOTAL OF 27 SECONDS. REF DAA2010-556-PW150A-FA0469 AND TC6-79-45. FOR CONTINUED SERVICEABILITY OF THE NR 1 ENGINE BEYOND 20 SECOND TRANSIENT PER DO. ALL OPS AND LEAK CHECKS GOOD. RETURNED TO SERVICE.