As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: NOTICED MUSTY SMELL AFTER TAKEOFF AT APPROXIMATELY 1000 FT. PREVIOUSLY WRITTEN UP. LASTED APPROXIMATELY 5 SECONDS THEN BEGAN DISSIPATING OVER THE NEXT MINUTE OR SO. MAINTENANCE FOUND RECIRC FILTERS VERY DIRTY AND REPLACED IAW AMM 21-25-01.