What was found
(CAN) DURING A TRAINING FLIGHT, ON A RECOVERY FROM A SIMULATED FORCED APPROACH ELEVATOR TRIM BECAME JAMMED IN THE FULL NOSE UP POSITION. ATTEMPTS WERE MADE TO TRIM THE AIRCRAFT MANUALLY & ELECTRICALLY BUT TRIM WHEEL WAS JAMMED SOLID. SIGNIFICANT PRESSURE ON THE YOKE WAS REQUIRED TO KEEP THE AIRPLANE LEVEL. CREW DECLARED AN EMERGENCY & RETURNED TO THE AIRPORT AFTER SELECTING DIFFERENT FLAP SETTINGS (AT ALTITUDE) TO SEE HOW THE AIRCRAFT WOULD RESPOND. ON DOWNWIND THE TRIM WAS THEN ABLE TO MOVE AGAIN & THE AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE IS PENDING. GOING THROUGH THE TRIM SYSTEM TO FIND THE PROBLEM.