B737 flight crew reported experiencing a 'severe' wake turbulence encounter on descent into ORD 10 miles in trail of a B777.
Synopsis
B737 flight crew reported experiencing a 'severe' wake turbulence encounter on descent into ORD 10 miles in trail of a B777.
Narrative
We were cleared to descend to 11000ft and 300kts on the WYNDE3 arrival into ORD; landing east. It was a beautiful evening with unrestricted visibility and smooth rides. The seatbelt sign was on and the flight attendants were wrapping up cabin prep for landing. As we leveled off around 11000 between WYNDE and FIYER; we encountered a moment of severe wake turbulence. It rolled the airplane around 25-30 degrees to the left and kicked off the autopilot. As PF; I rolled the wings back to level and maintained the steady pitch attitude and thrust setting. My captain told the flight attendants to be seated immediately as we encountered this wake and reported the severe turbulence to ATC. Within 5 seconds; the turbulence subsided. ATC informed us that we were 10 miles in trail of a 777; and my captain asked us to get vectored clear of their path. He then checked in with the flight attendants to make sure everybody was ok and that there were no injuries. We re-automated and were vectored to land on 9L uneventfully. Once parked at the gate; we called dispatch and the Chief Pilot to inform them of our severe wake turbulence encounter. We also submitted an Electronic Log Book (ELB) entry into the maintenance log. After discussing the situation with the Chief Pilot and maintenance crew; they decided that since this brief but severe encounter was due to the wake of another aircraft; the elb entry could be cancelled.
Second reporter narrative
As we were descending on the WYNDE3 arrival; we were instructed to maintain 11;000' and 300kts. We encountered wake turbulence and the aircraft's autopilot disconnected and we rolled approximately 20-25 degrees. We immediately corrected the aircraft's flight path and used our turbulence action guide. No injuries occurred. We initially reported severe turbulence to the controller after the shock of it; and he informed us that it was most likely due to wake from a heavy 777 that was 10 miles ahead. The aircraft was initially written up for severe wake turbulence; but after consulting with two Chief Pilots and maintenance; we concurred that the aircraft never encountered severe turbulence; but wake turbulence only. There was no technical fault with the aircraft; as the autopilot is designed to disconnect due to insufficient aileron authority. No upset was announced as we never met any of the bank/pitch/airspeed criteria. Upon conference with flight ops and maintenance; we agreed that voiding the write-up for the wake turbulence was appropriate; as it was not severe turbulence.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.