As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF AT APPROXIMATELY 600 FEET AGL, PILOT REPORTED THAT BOTH LEFT AND RIGHT FUEL BY-PASS ANNUNCIATORS ILLUMINATED, ACOMPANIED WITH PRONOUNCED ENGINE SURGING. AIRCRAFT RETURNED TO AIRPORT FOR UNEVENTFUL LANDING. MAINTENANCE LATER DETERMINED THAT THE CONDITION LEVER FRICTION LOCKS HAD NOT BEEN APPLIED, ALLOWING THE CONDITION LEVERS TO CREEP BACK TOWARD THE LOW RPM STOP.