FREIGHT HAULER ACFT DAMAGED AFTER ROLLING BACK INTO HANGAR WHEN PLTS LEAVE ACFT UNCHOCKED ON RAMP.

Narrative

AFTER ARRIVING AT CSV I PARKED THE AIRPLANE NEXT THE FUEL PUMPS. THERE WAS NOBODY ELSE AT THE ARPT; AND THE ARPT RAMP WAS DARK. AFTER SHUTTING THE ENGS DOWN; I EXITED THE AIRPLANE AND WENT TO PHONE IN MY ARR TO MY COMPANY'S DISPATCH. I LEFT THE PLT BEING TRAINED TO BEGIN UNLOADING THE AIRPLANE. HE UNLOADED THE AFT BAGGAGE COMPARTMENT (APPROX 3-5 MIN) AND CAME TO THE FSS TO USE THE RESTROOM. BEFORE LEAVING THE AIRPLANE I FAILED TO REMIND HIM TO CHOCK THE AIRPLANE. AFTER RETURNING TO THE AIRPLANE HE FOUND IT AGAINST THE HANGAR WITH DAMAGE TO BOTH ELEVATORS AND THE RUDDER. I BELIEVE THE CONTRIBUTING FACTORS TO THE INCIDENT INCLUDE A POORLY LIT RAMP (WHICH WAS BLACK TOP) AND MY FAILURE TO COMMUNICATE TO THE PLT IN TRAINING TO CHOCK THE AIRPLANE IF HE LEFT THE AREA. THE POORLY LIT RAMP CONCEALED THE SLOPE BEHIND THE AIRPLANE. UNFORTUNATELY; REPEATED TRIPS TO ARPTS WITH LEVEL RAMPS GETS ONE IN THE HABIT OF NOT CHOCKING AIRPLANES WHEN THE STAY IS BRIEF. ALWAYS CHOCKING WILL PREVENT FURTHER OCCURRENCES.