FLT CREW OF B767-300 EXPERIENCE UNCOMMANDED LEADING EDGE FLAP DEPLOYMENT ENRTE. DECLARE EMER AND LAND AT DEST WITH 20 DEGS FLAPS.

Narrative

ON DSCNT INTO ZZZ EARLIER THIS AFTERNOON; WE RECEIVED AN EICAS AURAL WARNING; AN EICAS MESSAGE OF 'LEADING EDGE FLAP ASYMMETRY;' THE ILLUMINATION OF THE 'LEADING EDGE' LIGHT NEAR THE FLAP INDICATOR ON THE FORWARD PANEL; AND THE FLAP INDICATOR NEEDLES (BOTH L AND R) WERE MATCHING AND POINTING TO 1/2 WAY BTWN 'UP' AND '1.' WE WERE NOT COMMANDING THE FLAPS TO MOVE AT ALL; WHICH IS WHY THIS PROB IS PARTICULARLY ODD. IN FACT; THE FLAP HANDLE HAD NOT BEEN TOUCHED SINCE FLAP RETRACTION ON CLBOUT FROM LAX. IT WAS COMPLETELY DOWN IN THE DETENT OF THE 'UP' POS. THE CAPT TURNED OFF THE AUTOPLT AND WE DID NOT NOTICE ANY INDICATIONS AT ALL THAT ANY LEADING EDGE DEVICES HAD BEEN EXTENDED. WE WERE AT APPROX 290 KTS WHEN THIS EVENT OCCURRED; SO WE SLOWED TO ABOUT 235 KTS; NOTIFIED CTR OF OUR AIRSPD; AND READ THE APPROPRIATE IRREGULAR CHKLIST. WE NOTED THAT THE STATEMENT IN THE 'CONDITIONS' OF THIS CHKLIST DID NOT APPLY; WHICH MENTIONED THAT FLAPS HAD BEEN COMMANDED TO MOVE WHEN THE EICAS MESSAGE APPEARED. THE CAPT COORD WITH ATC SOME DELAY VECTORS AND WE CHOSE RWY 9R SINCE IT WAS LONGER THAN THE RWY THEY WERE ORIGINALLY SENDING US TO (RWY 4R). AS THE CAPT FLEW AND TOOK THE RADIOS; I COMPLETED THE CHKLIST AND I ALSO COORD WITH DISPATCH (SECTOR 1). THE CAPT HAD ALREADY REQUESTED THE EMER VEHICLES TO BE STANDING BY; AND DISPATCH SAID THEY WOULD CONTACT MAINT ON OUR BEHALF AND CALL US BACK IF THEY HAD ANY FURTHER INSTRUCTIONS. WE WERE ABLE TO EXTEND THE TRAILING EDGE FLAPS USING THE FLAP HANDLE TO POS '20 DEGS' AND WE MADE AN UNEVENTFUL FLAPS 20 DEG LNDG WITH NO LEADING EDGE DEVICES. WE TAXIED TO THE GATE; LEAVING THE FLAPS IN POS AND COORD WITH MAINT. I THOUGHT THE CAPT DID AN EXCELLENT JOB HANDLING THIS SIT.