What was found
ON GEAR RETRACTION AFTER TAKE OFF, MULTIPLE ENGINE REPORTS LOUD AND ASSOCIATED VIBRATIONS ON ENG NR 1. SHUTDOWN NR 1 ENGINE IAW QRH. DUMPED FUEL RETURNED TO DEPARTURE. NO WING CAUTION MESSAGES OR ALERTS. AFT INSPECTION, FOUND 26 FAN BLADES DAMAGED. R & R NR 1 ENGINE DUE TO DAMAGE BEYOND LIMITS. REPLACEMENT CARRIED OUT IAW AMM 71-00-02-4 AND REPLACEMENT TEST CARRIED OUT. SATISFACTORY IAW AMM 71-00-00-705-156.