What was found
ON APPROACH INTO LAS, SELECTED FLAPS 25 & CAPTAIN NOTICED FLAPS BECAME ASYMMETRICAL LEAVING 20. NEVER RECEIVED ANY INDICATION ON ICAS. VERIFIED DETENT OF 25. ELECTED TO GO BACK TO 20. TRIED TO CYCLE FROM 20-25 AGAIN, STILL SHOWED A FLAP ASSYM, DECLARED AN EMERGENCY & DID A GO AROUND WHERE & EXECUTED TE FLAP ASSYM CHKLST & LANDED. R & R NR 1 POSITION FLAP POSITION TRANSMITTER ON LT WING AT OTBD FLAP IAW AMM 27-51-45-2. TRANSMITTER TARGET VALUES WITHIN MEASURED VALVES (DEG.). ALL COCKPIT FLAP POSITION INDICATIONS CHKD GOOD, BOTH NEEDLES NEVER SPLIT. OPS CHKD GOOD. R & R TE FLAP POSITION INDICATOR, OPS FLAPS TO EACH UNIT SEVERAL TIMES WITH NO FAULTS. OPS CHKD GOOD IAW AMM 27-58-02-4, & 27-58-00-5.