B737 Next Generation Undifferentiated
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Type 1066
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Procedure; Environment - Non Weather Related
I was First Officer and Pilot Monitoring for the flight in question. We had the autopilot and autothrottles engaged and were coupled to the localizer with approach mode selected and ALT Hold prior to GS intercept. While on approximately a 10 mile final to the ILS 8L at IAH; we experienced a quick (1-2 seconds) upset in the roll axis resulting in an uncommanded right roll in excess of 30 degrees. The feel of the upset was wake turbulence/vortex as flight conditions were mostly smooth prior to and after the event while on approach. As the aircraft rolled right; the yoke deflected nearly full left quickly followed by 'CWS ROLL' annunciation on the FMA. The Captain took immediate action in attempting to roll the aircraft level while in Control Wheel Steering (CWS) Roll and disconnected the autopilot shortly after. I called out the upset and called CWS Roll as the new FMA roll mode. The bank took the aircraft off center of the localizer although I don't recall how much. I believe it was not full deflection as I began calling to turn back left as we were deviating right. The Captain righted the aircraft and began to turn back to the left while hand flying the aircraft. At this point ATC called for us to turn left to rejoin the final approach course. I notified them that we had experienced a wake turbulence event that caused an uncommanded roll and that we were attempting to rejoin the localizer. ATC asked if we were able to continue the approach and we advised that we were able to do so. We asked what we were following and were told it was an E-170. We also asked what was on the parallel approach (8R) and were told it was also an E-170. It should be noted that the winds at 3000 feet were approximately 150/45 while lower in the approach they were 050/15. When we landed and taxied to hold short of 8R; we noted that a 747 landed before we crossed and taxied to the gate. As it had been a few minutes since we had landed we wondered where that heavy was in the approach pattern when we experienced the upset. We did debrief the event after the flight. We concluded that our actions were an appropriate response to the wake turbulence and upset that occurred. The decision to continue the approach when queried by ATC was largely based on the fact that the immediate recovery actions were to return to our course while maintaining altitude. We did not reach GS intercept until after we recovered from the upset.
Cleared for and established on the IAH ILS 8L; autopilot on and LOC/GS captured. Approximately 9 miles from touchdown and in the vicinity of FLIBZ; the aircraft rolled to the right to approximately 35 degrees. The autopilot remained engaged and as I counteracted the roll; the roll mode reverted to CWS; pitch mode remained captured. I disengaged the autopilot; rolled wings back to level and noticed we were approximately 3/4 scale deflection right of the localizer centerline. The First Officer was also aware of the situation and advised me to come back left to center the localizer. As we were correcting; ATC also notified us to correct to the left. We informed ATC that we had encountered what we thought was wake turbulence. We were asked if we were able to continue the approach. We had corrected the deviation; the aircraft was stabilized and again established on the localizer and glide slope and the autopilot was re-engaged. We answered ATC that we were able to continue the approach and we landed without incident.
B737NG flight crew reported encountering wake turbulence on approach to IAH.