Narrative:

Approaching point pintt the pilot flying (PF) took out the 2NM right slop in anticipation of entering radar controlled airspace. As we approached centerline of the track we started experience moderate wake turbulence from the aircraft approximated 15NM ahead of us and 1000 feet above us. I called to return to the offset; recognizing the turbulence was caused by the preceding aircraft's wake. The PF was slow to get back to the offset (seconds) as he attempted to return to the 2R offset by entering it in the FMS. The turbulence was great enough that as pilot monitoring I aided the PF by selecting a 15-20 degree heading change back to the offset the PF entered in the FMS. The wake turbulence caused the plane to start to climb. The plane may have corrected back on its own if left alone; but the PF initiated a descent with the vertical speed wheel passing about 100 feet high. The plane continued to climb as the autopilot was slow (milliseconds) to the vertical speed input. The PF then hit an altitude hold followed by another vertical speed descent input; which arrested the climb. We topped out approximate 410 feet high from our assigned altitude of FL290. The time from altitude deviation due to wake turbulence and back down to FL290 was less than 10 seconds. We could not have reacted quicker. The preceding aircraft was approximately 15 miles ahead of us. No TCAS traffic advisories or resolution advisories. The autopilot was never disengaged.if one keeps the slop offset until radar contact facilitates 2;000 feet vertical separation; one might have a better chance of avoiding wake turbulence and any altitude deviations caused by it.

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Original NASA ASRS Text

Title: MD-11 flight crew reported wake vortex encounter in cruise flight that resulted in an altitude deviation.

Narrative: Approaching point PINTT the Pilot Flying (PF) took out the 2NM right SLOP in anticipation of entering radar controlled airspace. As we approached centerline of the track we started experience moderate wake turbulence from the aircraft approximated 15NM ahead of us and 1000 feet above us. I called to return to the offset; recognizing the turbulence was caused by the preceding aircraft's wake. The PF was slow to get back to the offset (seconds) as he attempted to return to the 2R offset by entering it in the FMS. The turbulence was great enough that as pilot monitoring I aided the PF by selecting a 15-20 degree heading change back to the offset the PF entered in the FMS. The wake turbulence caused the plane to start to climb. The plane may have corrected back on its own if left alone; but the PF initiated a descent with the vertical speed wheel passing about 100 feet high. The plane continued to climb as the autopilot was slow (milliseconds) to the vertical speed input. The PF then hit an altitude hold followed by another vertical speed descent input; which arrested the climb. We topped out approximate 410 feet high from our assigned altitude of FL290. The time from altitude deviation due to wake turbulence and back down to FL290 was less than 10 seconds. We could not have reacted quicker. The preceding aircraft was approximately 15 miles ahead of us. No TCAS traffic advisories or resolution advisories. The autopilot was never disengaged.If one keeps the SLOP offset until radar contact facilitates 2;000 feet vertical separation; one might have a better chance of avoiding wake turbulence and any altitude deviations caused by it.

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.