What was found
PHL - FLT 452 - ON CLIMB-OUT FROM PHL, AT APPROX 5,000 FT, THE NR 1 ENGINE OIL FILTER BYPASS LIGHT ILLUMINATED. LIGHT REMAINED ON WHEN POWER WAS REDUCED TO IDLE THRUST ON THE NR 1 ENGINE. CREW SHUTDOWN THE NR 1 ENGINE IN FLIGHT AND RETURNED TO FIELD AT PHL WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. TOTAL SINGLE ENGINE TIME WAS 10 MINUTES. MAINTENANCE REMOVED AND INSPECTED THE NR 1 ENGINE OIL FILTER. NO CONTAMINATION FOUND. INSTALLED NEW OIL FILTER (P/N 056306-06) AND REPLACED OIL FILTER BYPASS SWITCH. ENGINE RUN CHECKS GOOD. (M)