A C560XL Captain reported the aircraft's elevator trim was jammed on takeoff and unresponsive either electrically or mechanically. Excessive control forces were required to control the aircraft. The crew returned to the departure airport.
Synopsis
A C560XL Captain reported the aircraft's elevator trim was jammed on takeoff and unresponsive either electrically or mechanically. Excessive control forces were required to control the aircraft. The crew returned to the departure airport.
Narrative
Departing in normal configuration noted that forward pressure on controls excessive; retracted flaps as per SOP; and pressure increased; also with speed pressure increased. Manual trim unresponsive. Trim wheel spun freely for several revolutions. Apparently elevator trim was jammed without ability to control manually or electrically. After consulting checklist discussed feasibility of no-flap landing; and after assessment determined a partial or full flap landing may be feasible. We therefore decided to return to our departure airport; and slowly tested flaps. Pressures were enough that knee was used behind the control column to counteract. Estimate 75-85 LBS at speeds over 200 KTS. One hundred pounds at 250 KTS; estimated. We managed neutral control pressures in the 140 to 180 KTS speed range at altitude after flap extension and therefore decided a full flap landing was feasible. The overweight landing was uneventful; and notifications and write ups were completed. This is the third Citation near disaster elevator trim malfunction I have experienced; I suggest possibly adding a thorough inspection to the system CSI checklist if other crews have had similar problems. The other instances were Mis-rigged elevator trim causing severe pitch up. The third instance was the trim mechanism had somehow been reversed (older Citation) causing reverse trim response.
NASA callback
The reporter stated that this was his third flight of the day with this aircraft and that the two previous flights had been normal. After the emergency; return maintenance personnel found the elevator trim cable had failed and became lodged in a pulley essentially preventing movement in either direction. The trim wheel spun freely because it was no longer connected. The checklists were of no help in this instance. There was no elevator flutter at any time during this event. The old Citations had a capstan trim cable assembly which was possible to get reversed during maintenance and thus reverse the controls. This aircraft had a threaded spindle which is much more straight forward and less likely to create a maintenance error. One of his previous events the controls were reversed because of the capstan problem and the crew nearly lost the aircraft when it pitch up 40 degrees as the elevator was moved forward. During the reporter's other elevator event; the reporter explained that as the trim wheel was removed; the index was not properly marked and when it was reinstalled is was mis-rigged causing the crew difficulty understanding why the aircraft was difficult to control. The old Citations had preflight procedure which required the crew to physically determine the trim position by a exiting the aircraft and verifying the elevator trims corresponding position.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.