As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAKEOFF, WITHIN 2 SECONDS OF SELECTING THE GEAR LEVER UP, HEARD A LOUD "THUMP". ALL THE GEAR GREEN LIGHTS EXTINGUISHED AND THE RED UNLOCK ANNUNCIATOR REMAINED ILLUMINATED. RAN EGINES INDEPENDENTLY APPLYING HYDRAULIC LOADS. DID NOT OBSERVE A "LOW HYD FLOW" FROM EITHER ENGINE DRIVEN PUMP. PERFORMED GEAR SWINGS AND WAS ABLE TO DUPLICATE PROBLEM. FOUND RT UPLOCK SWITCH AT FAULT . R & R RT MLG UPLOCK SWITCH IAW MM 32-61-00. OPS CHECKED GOOD.