Date: 201304
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Light: Daylight
Aircraft: Embraer Jet Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Gust Lock
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Troubleshooting; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Cruising at FL310 with autopilot engaged; the aircraft started to pitch up and down 300-600 FT/minute. We thought it was caused by the weather below us. All of a sudden the autopilot disengaged; I grabbed the yoke to stabilize the aircraft; but found it hard to control the pitch and could only stabilize the aircraft by using the Pitch Trim. Asked the First Officer to fly; he confirmed my findings. I then pulled the Elevator Disconnect lever; made no difference on my side; but the First Officer had immediate control. Ran the QRH; told Center our problem and that we would have to slow to 200 KTS as per QRH. He handed us off to Approach; told them our problem and declared an emergency. Landed with no problems and went to the gate. At the gate we engaged the Gust Lock. After a few minutes; I unlocked the Gust Lock to try my controls; found that my elevator control was full movement of the yoke; with no movement of the elevator. [We] wrote up aircraft; called Maintenance and Dispatch; unknown cause.

Callback: Reporter stated no problems with takeoff; elevators were free and responded. They did have to maneuver through clouds and around thunderstorms after takeoff. He does not recall any lightning strike occurring while flying. When the aircraft started pitching up and down; both control yokes had locked-up; no elevator movement with either control yoke until he pulled the Elevator Disconnect Handle. Only the First Officer's elevator became free to operate.Reporter stated that after gate arrival; when they had cycled the Gust Lock to the 'LOCK' position and than back to the 'FREE' (Unlocked) position; did he get full control yoke movement; but the elevator on his side still did not respond. He believes that was due to the Elevator Disconnect had not been reset. Maintenance told him later that his write-up was the first time they had heard about Gust Lock problems on Embraer aircraft and could not find anything wrong with the Gust Lock System. However; he flew the same airplane four days later and was amazed at how well the aircraft responded; he believes some type of maintenance had been accomplished on the aircraft.



Synopsis: Captain reports their Embraer aircraft started to pitch up and down 300-600 FPM. Autopilot suddenly disengaged and crew realized that both control yokes were locked-up with no elevator response. Gust Lock engagement was suspected; so the Captain pulled Elevator Disconnect Handle and First Officer's side then had immediate right elevator control.