B737-800
Flight Crew Air Transport Pilot (ATP)
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Environment - Non Weather Related; Procedure
On initial check-in with ORD Approach Control we were assigned Runway 27L. The Controller on the second Approach Control frequency gave us an intercept heading of 290 degrees to intercept the final approach course. Approximately one minute later the Controller's instructions were to turn to 250 degrees to re-intercept the final approach course. The pilot not flying informed the Controller that our 290 degree intercept heading looked good for [Runway] 27L. The Controller then stated that our assigned runway is 28C and we needed to turn to 250 degrees and then said 'I am not sure what runway I assigned you'. On our new heading of 250 degrees we intercepted the Runway 28C approach course approximately 25 NM out but were now only 3 NM from the proceeding aircraft. We then experienced a wake turbulence event which required the autopilot to be disconnected and power to be added. The pilot not flying informed the Controller that we were too close to the preceding aircraft and that we were slowing to 190 KTS. After this event the remainder of the approach and landing were uneventful.
I notified ATC of the wake turbulence encounter and that we were slowing to 190 KTS. The response back was; 'it was a 737-900 and it was the same type airplane and it should not be a problem.'  Well it was a problem and I had not yet been cleared for a visual approach yet and separation was the Controller's responsibility.  We slowed and the rest of the approach was uneventful.
A B737-800 encountered the wake vortices of a B737-900 on approach into ORD.