Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft
During climbout; the right seat pilot flying (PF) experienced difficulty trimming nose down while hand flying the aircraft.  We were cleared to FL210.  The PF is new to this model aircraft and thought he was doing something wrong when the trim would not initially move. He commented once the forces continued to increase so we leveled off at FL210 and proceeded to run checklists for the situation we encountered.  We referenced and completed the Electric Trim Inoperative Checklist as well as the Jammed Elevator Trim Checklist.  During our return to the field I spoke to the passengers and then declared an emergency to have equipment standing by. We assessed the control forces required at altitude and decided to configure early and higher than normal SOP to adjust for any issues we may encounter while configuring.  Once slowed and configured the control forces became more manageable. After landing and on the taxi in; I tried the trim again manually and it was still frozen in its current position.  During flight we were able to move the trim slightly rearward but never forward past the initial frozen point when assessing the situation. This has been an ongoing issue with this model aircraft.
During the climbout; after the flaps were selected up and I started to accelerate towards a normal climb speed of 250 knots; the electric elevator trim stopped would not allow me to trim the nose down. We tried the other electric elevator trim and the manual trim wheel; all would not trim nose down. We proceeded to level off at 21;000 FT; ran appropriate checklists; declared an emergency and returned to the departure airport for a visual approach and landing. The excessive back force on the yoke was neutralized as we configured for landing and the speed decreased. An uneventful emergency landing was successfully completed. ATC and airport crash/fire/rescue personnel were all extremely helpful during this event.
CE560 flight crew detects jammed elevator trim during climbout. After checklist procedures are unsuccessful an emergency is declared and the flight returns to the departure airport. The Captain states that 'This has been an ongoing issue with this model aircraft'.