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B737 first officer reported encountering wake turbulence in trail of a B777 at FL350 that resulted in a 45-60 degree roll.
| Attributes | |
| ACN | 1338476 |
| Time | |
| Date | 201603 |
| Place | |
| Locale Reference | ZHU.ARTCC |
| State Reference | TX |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Route In Use | STAR SKNRD 4 |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | B777 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 129 |
| Flight Phase | Descent |
| Route In Use | STAR SKNRD 4 |
| Flight Plan | IFR |
| Person 1 | |
| Function | First Officer Pilot Not Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 125 Flight Crew Type 762 |
| Events | |
| Anomaly | Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Wake Vortex Encounter |
Narrative:
Descending into iah via the sknrd arrival. We had been in-trail of a B777 for some time and had received speed assignments from ATC to maintain spacing. The B777 had been cruising at FL380. Our cruise altitude was FL360. The B777 began its descent around the same time as we did - possibly shortly before us. Shortly after beginning our descent; and at an estimated altitude of FL350; the aircraft rolled rapidly to the right. The FMA display showed a loss of LNAV and a degradation to cws right. I estimate that the maximum bank angle was in the range of 45 to 60 degrees to the right. The captain; who was the flying pilot; assumed manual control and recovered to a wings level descent. He ensured that the aircraft was under control and progressively returned us to MCP speed; LNAV; VNAV path and rejoined the arrival course. Shortly after the roll excursion; while we were still working to restore automation and turn back to course; ATC (houston center) noticed our track diverging from the arrival and inquired. We reported the wake turbulence encounter and that we were returning to course.I do not know the extent of our lateral deviation from the course but would estimate it to have been no more than three nautical miles--probably less. We did not deviate vertically from our ATC clearance. Once the aircraft was stabilized and the automation level restored I contacted the flight attendants and they reported that there were no injuries and they [were] okay in the back. The captain made an announcement regarding the event passengers. The seatbelt sign was on during the event. After the incident; ATC told us that we were 8NM in trail of the B777 and continued to manage our spacing via speed assignments on the arrival. I do not know why we encountered the wake turbulence as we were in full compliance with our ATC clearance which [should] have included adequate wake turbulence separation.
Original NASA ASRS Text
Title: B737 First Officer reported encountering wake turbulence in trail of a B777 at FL350 that resulted in a 45-60 degree roll.
Narrative: Descending into IAH via the SKNRD arrival. We had been in-trail of a B777 for some time and had received speed assignments from ATC to maintain spacing. The B777 had been cruising at FL380. Our cruise altitude was FL360. The B777 began its descent around the same time as we did - possibly shortly before us. Shortly after beginning our descent; and at an estimated altitude of FL350; the aircraft rolled rapidly to the right. The FMA display showed a loss of LNAV and a degradation to CWS R. I estimate that the maximum bank angle was in the range of 45 to 60 degrees to the right. The Captain; who was the flying pilot; assumed manual control and recovered to a wings level descent. He ensured that the aircraft was under control and progressively returned us to MCP SPEED; LNAV; VNAV PATH and rejoined the arrival course. Shortly after the roll excursion; while we were still working to restore automation and turn back to course; ATC (Houston Center) noticed our track diverging from the arrival and inquired. We reported the wake turbulence encounter and that we were returning to course.I do not know the extent of our lateral deviation from the course but would estimate it to have been no more than three nautical miles--probably less. We did not deviate vertically from our ATC clearance. Once the aircraft was stabilized and the automation level restored I contacted the flight attendants and they reported that there were no injuries and they [were] okay in the back. The Captain made an announcement regarding the event passengers. The seatbelt sign was on during the event. After the incident; ATC told us that we were 8NM in trail of the B777 and continued to manage our spacing via speed assignments on the arrival. I do not know why we encountered the wake turbulence as we were in full compliance with our ATC clearance which [should] have included adequate wake turbulence separation.
Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.