A CRJ700 CREW RPTS A MOMENTARY ELEVATOR PITCH LOCK WHILE EXERTING DOWNWARD YOKE PRESSURE AFTER TKOF AND AGAIN UPON LNDG.

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THE CAPT AND I WERE OPERATING A FLT. THIS WAS OUR SECOND DAY OF FLYING TOGETHER AND WE PERFORMED OUR PRE-TKOF CHKS; WHICH INCLUDED A FLT CTL CHK; AND ALL SYSTEMS APPEARED NORMAL. THE CAPT WAS THE PF AND I WAS THE PLT MONITORING. AFTER ROTATION; AT APPROX 700 FT AGL; THE CAPT SAID THAT HE WAS EXPERIENCING RESISTANCE IN LOWERING THE NOSE. I GLANCED AT OUR AIRSPD AND IT WAS WELL INTO THE SAFE RANGE. SIMULTANEOUSLY; I REPLIED; 'OK; I'M WITH YOU ON THE CTLS.' I THEN APPLIED ABRUPT FWD PRESSURE ON THE YOKE TO ASSIST THE CAPT. THE NOSE LOWERED AND THE CAPT REPLIED; 'IT'S GONE.' I STAYED WITH THE CAPT LIGHTLY ON THE CTLS AND WE BOTH HAD FULL CTL OF THE ACFT. I THEN ASKED THE CAPT IF HE WANTED TO TURN AROUND AND LAND. HE SAID; 'HOLD ON.' HE THEN CYCLED THE ACFT FROM THE AUTOPLT TO HAND FLY SEVERAL TIMES AND 'TESTED' THE CONTROLLABILITY OF THE ACFT. WE BOTH VERIFIED USING EQUIP ON THE ACFT THAT WE WERE GETTING 100 PERCENT RESPONSE TO THE INPUTS AGAIN. AFTER A FEW MOMENTS OF 'TESTING;' I ASKED THE CAPT AGAIN IF HE WANTED TO RETURN. THE CAPT REPLIED; 'LET'S CONTINUE.' AT THIS TIME I MADE AN INTERNAL ASSESSMENT OF HOW I FELT ABOUT HIS DECISION. THIS WAS THE SECOND LEG OF THE DAY; THE FIRST LEG WAS FROM ZZZ-ZZZ1; AND I WAS THE PF. I HAND FLEW THE TKOF; CLB; AND ACCELERATION THROUGH 10000 FT WITH NO ABNORMALITIES. AFTER ENGAGING THE AUTOPLT THROUGH CRUISE; I THEN HAND FLEW THE APCH AND LNDG WITH ABSOLUTELY NO PROBLEMS WHATSOEVER. WE ALSO PERFORMED TWO FLT CTL CHKS TO THE ACFT WITH NO ABNORMALITIES AND THE ANOMALY OCCURRED WITH THE CAPT AT THE CTLS. WHILE I EXPRESSED THE OPTION TO RETURN AND LAND TWICE; I CONCURRED WITH THE CAPT'S DECISION. HE FELT CONFIDENT THAT THE FLT WOULD CONTINUE SAFELY; AND I AS HIS FO; WAS THERE AS HIS SUPPORT. THROUGHOUT THE FLT; WE TRIED TO TROUBLESHOOT WHAT MIGHT HAVE LED TO THE ANOMALY; RANGING FROM A POSSIBLE 'SNAG' OF THE CTL YOKE ON HIS SEAT (HE SITS CLOSE) TO A MISCALCULATED STAB TRIM SETTING FOR TKOF. USING OUR DATA FROM THE GATE; I RECALCULATED OUR STAB TRIM SETTING AND CAME UP WITH THE SAME RESULT AS BEFORE. WE ALSO REVIEWED THE QRH PROCS IN CASE THE ANOMALY RETURNED. THE CAPT ROUTINELY CYCLED THE ACFT FROM AUTOPLT TO HAND FLYING TO 'TEST' THE FLT CTLS. THE ACFT REACTED WITH NO ABNORMALITIES. UPON ARR; THE CAPT REMOVED THE AUTOPLT ON A 7 MILE R BASE TO RWY 12R. AGAIN; THE CAPT 'TESTED' THE FLT CTLS TO ENSURE CONTROLLABILITY. THE ACFT BEHAVED NORMALLY THROUGH THE FLAP AND SLAT APPLICATIONS AND SPD REDUCTIONS. THE FLARE TO LNDG WAS NORMAL AND THE MAIN LNDG GEAR TOUCHED DOWN. DURING THE LOWERING OF THE NOSE GEAR TO THE RWY; THE CAPT EXPERIENCED SIMILAR RESISTANCE DURING THE FINAL SECOND. I WAS NOT TOUCHING THE FLT CTLS AT THE TIME AND WHEN THE NOSE TIRE TOUCHED; I LOOKED OVER TO FIND THE CAPT'S YOKE TO BE IN THE NORMAL; NEUTRAL POSITION. AT THAT MOMENT; THE CAPT MADE THE DECISION TO CONTACT MAINT. WHEN WE ARRIVED AT THE GATE; I CLRED THE AREA AROUND THE ACFT AND ACTIVATED ALL 3 HYDRAULIC SYSTEMS. I THEN PERFORMED SEVERAL THOROUGH FLT CTL CHKS IN VARIOUS INTERMEDIATE AND FULL DEFLECTION CONFIGURATIONS. I ALSO RAN THE STABILIZER TO ITS FULL MAX AND MIN SETTINGS. I EXPERIENCED NO ABNORMALITIES OR RESISTANCE (BELIEVE ME; I WAS LOOKING) IN THE FLT CTLS AND VERIFIED THE SAME THROUGH THE CAPT AND MECHANICS. WE THEN COORDINATED AND COOPERATED WITH MAINT TO SOLVE THE PROBLEM. TO THIS MOMENT; I HAVE NO IDEA WHAT COULD HAVE CAUSED THE ANOMALY; AND BECAUSE I WASN'T AT THE CTLS WHEN IT HAPPENED; I CANNOT DESCRIBE HOW IT FELT.SUPPLEMENTAL INFO FROM ACN 689263: CLBING OUT I NOTICED THE CTLS SEEMED TO BE LOCKING IN THE PITCH. I SAID TO THE FO THAT THE CTLS SEEMED TO BE LOCKED. HE THEN PUT HIS HANDS ON THE CTLS WITH ME. HE ALSO SAID HE FELT A RESISTANCE AND WITH THAT; THE CTLS FREED. I HAND FLEW FOR TIME AND THEN ENGAGED THE AUTOPLT. I THEN SAID FOR THE FO TO CHK THE STAB SETTINGS; WHICH HE DID. I CONFIRMED THE SETTING WAS CORRECT. AT THIS POINT; WE WERE WELL ON OUR WAY AND I ELECTED TO CONTINUE. THE FLT WAS UNEVENTFUL UNTIL THE LNDG. WHEN I PUT THE NOSE GEAR ON THE GND; AGAIN I NOTICED A PITCH LOCK. AT THE GATE I WROTE UP THE ACFT AND CALLED MAINT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT AS OF THIS DATE HE HAD NOT HEARD ANYTHING FORMAL FROM HIS ACR. INFORMALLY; A MAINT PERSON RELAYED THAT AN AUTOPLT SERVO MAY HAVE BEEN MALFUNCTIONING.