A B737-900 ON APCH AT 3000 FT EXPERIENCED LEADING EDGE AND TRAILING EDGES FLAPS STUCK AT 1 UNIT; EXECUTED GAR. ALTERNATE EXTENSION OK.

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UPON ARR INTO SEA; APPROX 10 MI FINAL AND SPD 215 KTS; FLAPS 1 DEG WAS SELECTED; THEN FLAPS 5 DEGS. GEAR WAS LOWERED AND FLAPS 15 DEGS SELECTED. IT WAS AT THIS POINT THAT I NOTICED THE FLAP GAUGE INDICATED FLAPS LESS THAN 1 DEG WITH A SLIGHT NEEDLE SPLIT. WE NOTIFIED TWR OF OUR NON NORMAL FLT CTL CONDITION; INITIATED A VERY GENTLE CLB; AND REQUESTED A L EXTENDED DOWNWIND. AS WE OVERFLEW THE ARPT; I NOTICED THAT THE AMBER LEADING EDGE FLAPS TRANSIT LIGHT WAS NOW ILLUMINATED AND THERE WAS NO LONGER A SPLIT NEEDLE CONDITION ON THE FLAP GAUGE; THOUGH THE INDICATION REMAINED AT LESS THAN 1 DEG. I ACCOMPLISHED THE LEADING EDGE FLAP TRANSIT DURING FLAP EXTENSION CHKLIST WHICH DIRECTED ME TO THE SYMMETRICAL TRAILING EDGE FLAP FAILURE/ALTERNATE FLAPS OP CHKLIST. BEFORE INITIATING THIS CHKLIST; I TALKED WITH THE FLT ATTENDANTS AND THEN NOTIFIED SEA MAINT CTL OF OUR SIT. THEY AFFIRMED THE CHKLIST I WAS ABOUT TO BEGIN AND SUGGESTED CYCLING THE FLAPS TO 'UP.' I SLOWLY RAISED THE LEVER TO 'UP;' BUT THE INDICATIONS DID NOT CHANGE -- SYMMETRICAL NEEDLES INDICATING LESS THAN 1 DEG; ALL LEADING EDGE DEVICES IN THE 'EXT' POS; AND THE LEADING EDGE FLAPS TRANSIT LIGHT ILLUMINATED. I BEGAN THE ALTERNATE FLAPS OP CHKLIST AND CONFIRMED THAT THE FLAPS AND LEADING EDGE DEVICES WERE RESPONDING TO THE ALTERNATE EXTENSION METHOD. I THEN VERIFIED FLAPS 15 DEGS DATA FOR SEA. WE TURNED BACK TOWARD THE ARPT; ACCEPTED AN OFFER TO HAVE EMER EQUIP STANDING BY; AND COMPLETED THE ALTERNATE FLAPS OP CHKLIST BY APPROX 12 MI FINAL. I ONCE AGAIN TALKED WITH THE FLT ATTENDANTS AND THEN MADE A PA ANNOUNCEMENT AS TO WHAT HAD OCCURRED TO CAUSE OUR DELAY IN LNDG; THAT WE HAD CORRECTED THE MALFUNCTION; AND WOULD BE LNDG IN 34 MINS. WE MADE A FLAPS 15 DEG LNDG AND TAXIED UNASSISTED TO THE GATE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE TRAILING EDGE FLAPS AND LEADING EDGE DEVICES TO EXTEND IS UNKNOWN. THE RPTR SAID MAINT HAS NOT RPTED ANY COMPONENT OR ACTION TAKEN TO THE CREW.