Narrative:

En route from ZZZ1 to ZZZ2 in cruise at 29000 ft when the gust lock light illuminated. We immediately decided not to touch the controls, leaving the aircraft on autoplt for the time being. Captain went to the aom vol 1 and read the appropriate procedure. We agreed the most important thing was to keep the yoke as far from the forward stop as possible, so the first officer (PF) slowed the plane to 230 KIAS to increase aoa and backpressure on yoke. The captain informed center and declared an emergency. He sent a message to dispatch requesting nearest large airport with minimum winds while pulling up ATIS for ZZZ1 and ZZZ (we were still about 45 minutes from ZZZ2). After briefing the flight attendant, we decided to divert to ZZZ (closest and winds 4 KTS). Captain made PA while the first officer flew a slow IAS descent, deviating to remain VMC and out of any turbulent buildups. The airport was acquired visually at about 25 NM. In order to avoid any lurching when the autoplt was disengaged, the PF first applied backpressure and pressed the tcs button, then disengaged the autoplt. We flew a wide slow turn to a visual final, configuring the aircraft at or near minimum speeds to maintain as high an aoa as possible, and therefore as much backpressure as possible to keep the yoke as far from the forward stop as we could. The approach was followed by an uneventful landing. Callback conversation with reporter revealed the following information: the reporter stated the gust lock function should only work on the ground when parked. The reporter said the gust lock only locks the throttles and elevators. The reporter stated the rudder and ailerons are hydraulically powered and are dampened, but the elevators are cable operated and need locking. The reporter said when applying the gust lock on the ground it locks the throttles mechanically, but the elevators are locked electrically by powering an electric motor at or near the aft elevator quadrant. The reporter stated the gust lock light is on only when the elevator gust lock motor is powered and extending a lock pin into the elevator quadrant. The reporter said the quadrant has a hole that when the yoke is pushed full forward, it aligns with the motor driven pin and locks the elevators. The reporter stated the light then goes out and the motor is unpowered. The uncommanded operation of the elevator gust lock is a serious concern.

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Original NASA ASRS Text

Title: AN EMBRAER 135 IN CRUISE AT FL290 DECLARED AN EMER AND DIVERTED DUE TO GUST LOCK LIGHT ILLUMINATING IN FLT.

Narrative: ENRTE FROM ZZZ1 TO ZZZ2 IN CRUISE AT 29000 FT WHEN THE GUST LOCK LIGHT ILLUMINATED. WE IMMEDIATELY DECIDED NOT TO TOUCH THE CTLS, LEAVING THE ACFT ON AUTOPLT FOR THE TIME BEING. CAPT WENT TO THE AOM VOL 1 AND READ THE APPROPRIATE PROC. WE AGREED THE MOST IMPORTANT THING WAS TO KEEP THE YOKE AS FAR FROM THE FORWARD STOP AS POSSIBLE, SO THE FO (PF) SLOWED THE PLANE TO 230 KIAS TO INCREASE AOA AND BACKPRESSURE ON YOKE. THE CAPT INFORMED CTR AND DECLARED AN EMER. HE SENT A MESSAGE TO DISPATCH REQUESTING NEAREST LARGE ARPT WITH MINIMUM WINDS WHILE PULLING UP ATIS FOR ZZZ1 AND ZZZ (WE WERE STILL ABOUT 45 MINUTES FROM ZZZ2). AFTER BRIEFING THE FLIGHT ATTENDANT, WE DECIDED TO DIVERT TO ZZZ (CLOSEST AND WINDS 4 KTS). CAPT MADE PA WHILE THE FO FLEW A SLOW IAS DSCNT, DEVIATING TO REMAIN VMC AND OUT OF ANY TURBULENT BUILDUPS. THE ARPT WAS ACQUIRED VISUALLY AT ABOUT 25 NM. IN ORDER TO AVOID ANY LURCHING WHEN THE AUTOPLT WAS DISENGAGED, THE PF FIRST APPLIED BACKPRESSURE AND PRESSED THE TCS BUTTON, THEN DISENGAGED THE AUTOPLT. WE FLEW A WIDE SLOW TURN TO A VISUAL FINAL, CONFIGURING THE ACFT AT OR NEAR MINIMUM SPEEDS TO MAINTAIN AS HIGH AN AOA AS POSSIBLE, AND THEREFORE AS MUCH BACKPRESSURE AS POSSIBLE TO KEEP THE YOKE AS FAR FROM THE FORWARD STOP AS WE COULD. THE APCH WAS FOLLOWED BY AN UNEVENTFUL LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE GUST LOCK FUNCTION SHOULD ONLY WORK ON THE GND WHEN PARKED. THE RPTR SAID THE GUST LOCK ONLY LOCKS THE THROTTLES AND ELEVATORS. THE RPTR STATED THE RUDDER AND AILERONS ARE HYDRAULICALLY POWERED AND ARE DAMPENED, BUT THE ELEVATORS ARE CABLE OPERATED AND NEED LOCKING. THE RPTR SAID WHEN APPLYING THE GUST LOCK ON THE GND IT LOCKS THE THROTTLES MECHANICALLY, BUT THE ELEVATORS ARE LOCKED ELECTRICALLY BY POWERING AN ELECTRIC MOTOR AT OR NEAR THE AFT ELEVATOR QUADRANT. THE RPTR STATED THE GUST LOCK LIGHT IS ON ONLY WHEN THE ELEVATOR GUST LOCK MOTOR IS POWERED AND EXTENDING A LOCK PIN INTO THE ELEVATOR QUADRANT. THE RPTR SAID THE QUADRANT HAS A HOLE THAT WHEN THE YOKE IS PUSHED FULL FORWARD, IT ALIGNS WITH THE MOTOR DRIVEN PIN AND LOCKS THE ELEVATORS. THE RPTR STATED THE LIGHT THEN GOES OUT AND THE MOTOR IS UNPOWERED. THE UNCOMMANDED OPERATION OF THE ELEVATOR GUST LOCK IS A SERIOUS CONCERN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.