Narrative:

During initial climb through approximately 1;500 feet; we encountered wake turbulence from the preceding aircraft that caused the aircraft to bank approximately 10-15 degrees to the right. I was the pilot flying (PF) and first guarded the controls; but the roll seemed like it was going to continue and I decided to not let it go further; so I disengaged the autopilot (a/P) to correct the flight path. We were very busy at this stage of flight with a clearance and radio call from our initially assigned 3;000 feet to a new clearance to climb 6;000 feet. We were also in the process of cleaning up the flaps to flaps 1 and had a 230 knot speed restriction until above 4000 feet on the wsss vmr 5A SID. Believing we were clear of the wake turbulence; we tried to reengage the a/P but it disconnected; so I continued to fly. We proceeded to select flaps up on schedule as normal with our airspeed increasing toward clean maneuvering speed of 226 knots; we then encountered wake turbulence a 2nd time. After it smoothed out; we again tried to reengage the a/P; but it disconnected or didn't engage; I continued to fly the airplane. We then encountered wake turbulence a third time and a brief stick shaker occurred (1 sec) as we were approximately 10 knots under our clean maneuvering speed of 226 and attempting to accelerate to no greater than 230 knots per the SID. Of course there was also a lot going on with the a/P disconnect warnings sounding twice; but the aircraft was under control; and I did not observe that I was too close to the pilot limit indicator (pli) until the shaker sounded. In fact; it seemed to me that the pli disappeared at or near this point in the climb; and came back on simultaneously with the brief shaker - at least that's what I thought I saw. I quickly recovered from the shaker and we waited a bit before reattempting to engage the a/P; which we did successfully. Aside from the brief warning that occurred while in turbulence and a less than perfect lateral track on the SID; I felt that the aircraft was in control throughout the event. I feel the momentary stick shaker was likely the combination of being 10 knots slower than clean maneuvering speed at a heavier weight; and the wake turbulence causing a sudden change in angle of attack. In retrospect; maintaining flaps 1 until clear of the turbulence might have worked better; but there was a lot going on in the moment; and I thought we were clear of the turbulence after each encounter so I continued to fly the normal flap cleanup profile while mindful to not exceed 230 knots. The 230-knot restriction played a part in my reluctance to accelerate too quickly to 226 and thus may have also played a part in why I was a bit slow as we hit the last wake turbulence. I feel we did the best we could given the complexities of the situation. As a side note to my recollection; the tower did not advise us we were behind a heavy; and I was not aware given that it was dark as we taxied. Fatigue is always an issue flying international with multiple circadian flips.

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Original NASA ASRS Text

Title: B767-300 flight crew reported speed and track deviations occurred following a wake turbulence encounter departing WSSS.

Narrative: During initial climb through approximately 1;500 feet; we encountered wake turbulence from the preceding aircraft that caused the aircraft to bank approximately 10-15 degrees to the right. I was the Pilot Flying (PF) and first guarded the controls; but the roll seemed like it was going to continue and I decided to not let it go further; so I disengaged the Autopilot (A/P) to correct the flight path. We were very busy at this stage of flight with a clearance and radio call from our initially assigned 3;000 feet to a new clearance to climb 6;000 feet. We were also in the process of cleaning up the flaps to flaps 1 and had a 230 knot speed restriction until above 4000 feet on the WSSS VMR 5A SID. Believing we were clear of the wake turbulence; we tried to reengage the A/P but it disconnected; so I continued to fly. We proceeded to select flaps up on schedule as normal with our airspeed increasing toward clean maneuvering speed of 226 knots; we then encountered wake turbulence a 2nd time. After it smoothed out; we again tried to reengage the A/P; but it disconnected or didn't engage; I continued to fly the airplane. We then encountered wake turbulence a third time and a brief stick shaker occurred (1 sec) as we were approximately 10 knots under our clean maneuvering speed of 226 and attempting to accelerate to no greater than 230 knots per the SID. Of course there was also a lot going on with the A/P disconnect warnings sounding twice; but the aircraft was under control; and I did not observe that I was too close to the Pilot Limit Indicator (PLI) until the shaker sounded. In fact; it seemed to me that the PLI disappeared at or near this point in the climb; and came back on simultaneously with the brief shaker - at least that's what I thought I saw. I quickly recovered from the shaker and we waited a bit before reattempting to engage the A/P; which we did successfully. Aside from the brief warning that occurred while in turbulence and a less than perfect lateral track on the SID; I felt that the aircraft was in control throughout the event. I feel the momentary stick shaker was likely the combination of being 10 knots slower than clean maneuvering speed at a heavier weight; and the wake turbulence causing a sudden change in angle of attack. In retrospect; maintaining flaps 1 until clear of the turbulence might have worked better; but there was a lot going on in the moment; and I thought we were clear of the turbulence after each encounter so I continued to fly the normal flap cleanup profile while mindful to not exceed 230 knots. The 230-knot restriction played a part in my reluctance to accelerate too quickly to 226 and thus may have also played a part in why I was a bit slow as we hit the last wake turbulence. I feel we did the best we could given the complexities of the situation. As a side note to my recollection; the Tower did not advise us we were behind a heavy; and I was not aware given that it was dark as we taxied. Fatigue is always an issue flying international with multiple circadian flips.

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.