A CRJ-200 experienced a failure of the flap/slat control mechanism on final approach. The flight crew initiated a go around; declared an emergency and landed without incident.

Narrative

I was the pilot flying on final approach. The aircraft was configured at Flaps 20 with gear up. Soon after passing the FAF; with the aircraft stable at 170 knots and auto pilot engaged; I called for Gear Down; Flaps 30; and Before Landing Checklist. The Captain extended the gear; then selected Flaps 30. Upon Flaps 30 selection; the yellow 'Flaps Fail' caution message appeared. The flaps indicated 20 degrees. I initiated a smooth and gradual go around; and Tower was notified of our intentions. Tower assigned heading and altitude. I retained pilot flying duties and accepted control of the radio while the Captain performed the QRH checklist. The checklist did not correct the flaps failure. We discussed the problem and notified ATC of our problem and declared an emergency. Approach was stable by 1000 ft; with a Vref of 165 knots. Day VMC with a crosswind of 15 knots existed. The aircraft landed smoothly and was slowed without excessive braking despite one thrust reverser INOP per MEL. We taxied to the gate with no further problems or concerns.