A CE-750 flight crew declared an emergency and diverted when elevator pitch inputs jammed; causing abnormal stabilizer trim inputs to compensate for ineffective elevator inputs.
Synopsis
A CE-750 flight crew declared an emergency and diverted when elevator pitch inputs jammed; causing abnormal stabilizer trim inputs to compensate for ineffective elevator inputs.
Narrative
After engine start during the flight control check the Captain made a comment during the aileron check that the controls felt a bit heavy but became normal as an additional actuation was completed. Additional actuations felt normal so we attributed this to picking up a cold-soaked airplane. Pitch and rudder controls were normal. The entire flight was VMC with no turbulence.The flight was normal until climbing through FL300 towards our assigned altitude of FL430. The Captain first became aware of excessive 'clacker' noises caused by the pitch trim system. He disconnected the autopilot and stated that the pitch controls were stuck. I tried mine too and they were stuck. We agreed to stop the climb. At this point we reconfirmed that we were actually having a flight control issue and really needed to divert and land. I don't remember the sequence but we received a clearance to FL200 and ATC advised that ZZZ was at 1 o'clock and approximately 30 miles away. They gave us a 270 heading for vectors to the airport.We agreed to split the controls per the aileron/pitch jam memory items. When we did this the copilot's pitch controls remained jammed and the pilot's seemed free. I finished the pitch jam checklist as we were descending. Also I was trying to get charts and weather for the diversion airport. We were leveling at FL200 at this point and I could see ZZZ in the distance.All seemed okay until the Captain said his controls felt jammed. But then they freed up so we continued the descent towards the airport and ran the approach and landing checklists. Slowing; we added flaps 5 without problems (we had discussed retracting the flaps if something abnormal occurred). When we added flaps 15; the Captain briefly complained about his controls but then affirmed they were OK again before I retracted the flaps. I asked/suggested not going any further with the flaps and the Captain agreed so I got flaps 15 numbers from the FMS.The approach and landing was stable and felt well controlled. I think at this point the Captain had a feel where any binding would likely occur and he trimmed the plane to avoid putting the elevator there. We touched down normally and taxied off under our own power.
Second reporter narrative
Climbing out of approximately 28;000 FT; we began to get a series of trim clackers (automatic pitch trims in excess of three seconds activates the clacker). We got a total of three clackers before I started questioning the abnormal presence of them for those conditions. I commented about the clackers to my partner.It seemed that pushing the nose down (yoke forward of neutral); was causing a stoppage/binding in the forward movement of the yoke. At first I thought the stiff elevator movement was due to Mach trim increasing the forces necessary to pitch the aircraft at these higher speeds. As I tried to push the nose over to reduce the rate of climb; I found the force necessary to push the nose forward to be excessive and restrictive; making it unable for me to slow the rate of climb without using the pitch trim. Pitch trim seemed to work absolutely normally.ATC asked us if we wanted them to roll the trucks. We said roll the trucks.After aircraft shutdown and battery switch selected off; copilot discovered his pitch was still jammed. He increased his pressure and broke the bind; after which his yoke moved forward and aft with some catching.I debriefed the lead mechanic at the Cessna service station.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.