Standard speed is 220 knots on downwind, 180 on base, and 160 on final.
The Avro RJ requires a stabilized approach. Use the airbrake to manage speed, and ensure you are at VREF+5 knots, with landing gear down and flaps 33 by 1,000 feet. Mahan Air livery for Avro RJ100 X-plane11 - X-Plane.org