Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 130
Workload
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Environment - Non Weather Related; Aircraft
Approaching SADDE intersection; descending from 12;000 feet to 10;000 feet and slowing to 210 knots; we encountered moderate plus wake turbulence from heavy 777 in calm air; causing autopilot to revert to CWS from LNAV/VNAV CMD mode. After arresting control from wake rolling tendency; we overshot SADDE intersection and had to manually turn towards BAYST intersection before re-engaging LNAV/VNAV CMD mode. We were advised at the same time by ATC to turn immediately towards BAYST. Just prior to autopilot disconnect; we had advised ATC of the wake turbulence upset. Remainder of flight was uneventful after we reported heavy aircraft in sight for visual approach and remained above its glidepath.
Prior to SADDE we encountered moderate wake turbulence. It seemed to last longer than usual; and the pilot flying was struggling to maintain aircraft control. I told ATC we were in wake turbulence and asked what we were following. The reply was 'a heavy'. We later learned it was a 777. During the event the autopilot reverted to CWS. I saw this happen but did not announce it; due to the high workload the Captain was under. As we approached SADDE the wake was subsiding but we were still in CWS; in zero wind so it appeared we were on course on the MFD. I still did not announce CWS due to other distractions and concerns about the wake. We then flew past SADDE and did not turn toward to BAYST.
B737 flight crew reported track deviation on approach to LAX when the autopilot reverted to control wheel steering in response to a wake turbulence encounter.