Narrative:

Yaw damper tripped off and was reset. Within 1-2 mins, flaps and leading edge devices began to deploy with no movement of flap handle. Flap handle was pushed forward with no detectable movement of lever. Within 1 min, flaps and leading edge devices retracted. Autoplt was disengaged and descent initiated to FL250 and diversion to nearest airport (phx) was made. Air conditioning pressure was split abnormally high between left/right right = 50 psi and left = 10 psi in-flight as well. Normal approach and landing made into phx with flaps 30 degrees and autobrakes 3 degrees. Upon landing, left (#1) engine control light was also illuminated. Since aircraft remained under positive control, no emergency was declared. Supplemental information from acn 577384: flight was at FL390, steady state cruise, approximately .80 mach, indicated airspeed unknown. The master caution and yaw damper lights illuminated. The yaw damper switch was re-engaged and the yaw damper light extinguished. Shortly after, the leading edge in transit lights (amber) on the overhead panel were observed on, followed by the leading edge flaps in transit lights on the forward panel. The trailing edge flaps gauge was also observed indicating approximately 1/2 degree extended. Both the captain and the first officer physically and visually verified that the flap handle was in the up detent. I accomplished the after takeoff checklist after departing las vegas and specifically remember confirming that the flap handle was in the up detent and that the flap gauge indicated full up. Also, I looked at the leading edge device lights on the overhead panel and confirmed that they were fully retracted. After the abnormal flap indications were observed, we also noted a 40 psi difference between the left and right duct pressures on the overhead panel. In addition, the ram air doors open lights were illuminated. I referred to the QRH, but found that no procedure for this condition exists. The flaps and leading edge devices retracted to full up without pilot input. The autoplt was disconnected and a descent divert to phoenix, az, was initiated. During the descent, the aircraft was configured for landing. No anomalies were detected. We did not declare an emergency because we had no need for the emergency vehicles. We had phoenix in sight from approximately 10 mi out and visually acquired the airport prior to configuring. There was no other traffic, therefore, we felt that we did not require ATC priority handling. We accomplished an uneventful 30 degree flaps landing at phx. Callback conversation with reporter revealed the following information: after landing, the air carrier did a complete flight recorder readout. Takeoff showed the flap handle was retracted and in the up detent, however, the actual flap position was slightly out of the 'up' position. This apparently caused the leading edge slats to start extension. The aircraft did not have any vibration or buffet that would indicate actual slat extension. The autoplt was turned off as soon as the in transit light illuminated, and there was no roll or turning tendency. The crew was debriefed by the air carrier chief pilot's office. The crew was requested to fly the air carrier -800 simulator in an attempt to duplicate the problem. They were unable to duplicate the problem in the simulator. After a slight rigging adjustment in the flap handle system, the aircraft was test flown. The problem did not recur on the test flight, nor has it recurred since then. The captain did not know the causes of the other problems he had.

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Original NASA ASRS Text

Title: A B737-800 IN CRUISE AT FL390 HAD YAW DAMPER TRIP. WITHIN 1-2 MINS THE FLAPS AND LEADING EDGE DEVICES BEGAN TO DEPLOY WITH NO FLAP HANDLE MOVEMENT.

Narrative: YAW DAMPER TRIPPED OFF AND WAS RESET. WITHIN 1-2 MINS, FLAPS AND LEADING EDGE DEVICES BEGAN TO DEPLOY WITH NO MOVEMENT OF FLAP HANDLE. FLAP HANDLE WAS PUSHED FORWARD WITH NO DETECTABLE MOVEMENT OF LEVER. WITHIN 1 MIN, FLAPS AND LEADING EDGE DEVICES RETRACTED. AUTOPLT WAS DISENGAGED AND DSCNT INITIATED TO FL250 AND DIVERSION TO NEAREST ARPT (PHX) WAS MADE. AIR CONDITIONING PRESSURE WAS SPLIT ABNORMALLY HIGH BTWN L/R R = 50 PSI AND L = 10 PSI INFLT AS WELL. NORMAL APCH AND LNDG MADE INTO PHX WITH FLAPS 30 DEGS AND AUTOBRAKES 3 DEGS. UPON LNDG, L (#1) ENG CTL LIGHT WAS ALSO ILLUMINATED. SINCE ACFT REMAINED UNDER POSITIVE CTL, NO EMER WAS DECLARED. SUPPLEMENTAL INFO FROM ACN 577384: FLT WAS AT FL390, STEADY STATE CRUISE, APPROX .80 MACH, INDICATED AIRSPD UNKNOWN. THE MASTER CAUTION AND YAW DAMPER LIGHTS ILLUMINATED. THE YAW DAMPER SWITCH WAS RE-ENGAGED AND THE YAW DAMPER LIGHT EXTINGUISHED. SHORTLY AFTER, THE LEADING EDGE IN TRANSIT LIGHTS (AMBER) ON THE OVERHEAD PANEL WERE OBSERVED ON, FOLLOWED BY THE LEADING EDGE FLAPS IN TRANSIT LIGHTS ON THE FORWARD PANEL. THE TRAILING EDGE FLAPS GAUGE WAS ALSO OBSERVED INDICATING APPROX 1/2 DEG EXTENDED. BOTH THE CAPT AND THE FO PHYSICALLY AND VISUALLY VERIFIED THAT THE FLAP HANDLE WAS IN THE UP DETENT. I ACCOMPLISHED THE AFTER TKOF CHKLIST AFTER DEPARTING LAS VEGAS AND SPECIFICALLY REMEMBER CONFIRMING THAT THE FLAP HANDLE WAS IN THE UP DETENT AND THAT THE FLAP GAUGE INDICATED FULL UP. ALSO, I LOOKED AT THE LEADING EDGE DEVICE LIGHTS ON THE OVERHEAD PANEL AND CONFIRMED THAT THEY WERE FULLY RETRACTED. AFTER THE ABNORMAL FLAP INDICATIONS WERE OBSERVED, WE ALSO NOTED A 40 PSI DIFFERENCE BTWN THE L AND R DUCT PRESSURES ON THE OVERHEAD PANEL. IN ADDITION, THE RAM AIR DOORS OPEN LIGHTS WERE ILLUMINATED. I REFERRED TO THE QRH, BUT FOUND THAT NO PROC FOR THIS CONDITION EXISTS. THE FLAPS AND LEADING EDGE DEVICES RETRACTED TO FULL UP WITHOUT PLT INPUT. THE AUTOPLT WAS DISCONNECTED AND A DSCNT DIVERT TO PHOENIX, AZ, WAS INITIATED. DURING THE DSCNT, THE ACFT WAS CONFIGURED FOR LNDG. NO ANOMALIES WERE DETECTED. WE DID NOT DECLARE AN EMER BECAUSE WE HAD NO NEED FOR THE EMER VEHICLES. WE HAD PHOENIX IN SIGHT FROM APPROX 10 MI OUT AND VISUALLY ACQUIRED THE ARPT PRIOR TO CONFIGURING. THERE WAS NO OTHER TFC, THEREFORE, WE FELT THAT WE DID NOT REQUIRE ATC PRIORITY HANDLING. WE ACCOMPLISHED AN UNEVENTFUL 30 DEG FLAPS LNDG AT PHX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AFTER LNDG, THE ACR DID A COMPLETE FLT RECORDER READOUT. TKOF SHOWED THE FLAP HANDLE WAS RETRACTED AND IN THE UP DETENT, HOWEVER, THE ACTUAL FLAP POS WAS SLIGHTLY OUT OF THE 'UP' POS. THIS APPARENTLY CAUSED THE LEADING EDGE SLATS TO START EXTENSION. THE ACFT DID NOT HAVE ANY VIBRATION OR BUFFET THAT WOULD INDICATE ACTUAL SLAT EXTENSION. THE AUTOPLT WAS TURNED OFF AS SOON AS THE IN TRANSIT LIGHT ILLUMINATED, AND THERE WAS NO ROLL OR TURNING TENDENCY. THE CREW WAS DEBRIEFED BY THE ACR CHIEF PLT'S OFFICE. THE CREW WAS REQUESTED TO FLY THE ACR -800 SIMULATOR IN AN ATTEMPT TO DUPLICATE THE PROB. THEY WERE UNABLE TO DUPLICATE THE PROB IN THE SIMULATOR. AFTER A SLIGHT RIGGING ADJUSTMENT IN THE FLAP HANDLE SYS, THE ACFT WAS TEST FLOWN. THE PROB DID NOT RECUR ON THE TEST FLT, NOR HAS IT RECURRED SINCE THEN. THE CAPT DID NOT KNOW THE CAUSES OF THE OTHER PROBS HE HAD.

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.