As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON GEAR RETRACTION A LOUD "KNOCKING" NOISE WAS HEARD, NO CAUTION OR WARNING MESSAGES RECEIVED BUT NOISE CONTINUED. FOLLOWED QRH AND DECIDED TO RETURN TO DTW, DECLARED EMERGENCY AND LANDED WITHOUT INCIDENT. NOSE GEAR DOOR ACTUATOR RE-RIGGED AND OPERATIONAL CHECK PERFORMED IAW BOMBARDIER AMM. (S)