Narrative:

While descending on the fytte 2 arrival; with a clearance to cross bhawk at 240 ATC re-cleared us to descend via the fytte 2 except maintain 300 knots. At this point we were about ten miles west of bhawk descending in LNAV and VNAV. The altitude window was reset from 240 to 11000. I put 300 knots in the speed window. I then edited the speed on the VNAV descent page to 300 knots and edited the speed restrictions on the legs page at stnle and cuupp to 300. After executing these revisions I noticed the airplane began an uncommanded right turn off of the magenta line. At this point I hit heading select and slewed the heading cursor back around to re-intercept the magenta line. I now noticed that although the magenta line still went through bhawk the fix itself had turned white and stnle the next fix on the arrival had become active. I rearmed LNAV; but it did not capture as we flew back through the course; so I slewed the heading select back towards bhawk. The airplane was slow to respond; so I disconnected the autopilot and was now hand flying to bhawk. As we approached bhawk ATC asked if we are still descending via the fytte 2. The co-pilot then said we need to cross bhawk above 220 and informs me that I am already low and still descending. I leveled off and we crossed bhawk below 220. In the confusion of losing the bhawk fix and flying the aircraft back to the now white fix indication I had not realized that the FMC had lost the vertical crossing restrictions at bhawk. After passing bhawk the flight director recaptured the magenta line into stnle and the VNAV path came back. I re-engaged the autopilot with no further problems.my opinion of the overall problem here is we do too much typing and not enough flying.

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Original NASA ASRS Text

Title: While descending on the ORD FYTTE2; ATC issued a 300 knot speed restriction. When the B777 Captain modified the waypoint speed constraints it caused LNAV and VNAV to disconnect. The aircraft descended below profile and deviated from the desired heading until manually corrected.

Narrative: While descending on the FYTTE 2 Arrival; with a clearance to cross BHAWK at 240 ATC re-cleared us to descend via the FYTTE 2 except maintain 300 knots. At this point we were about ten miles west of BHAWK descending in LNAV and VNAV. The altitude window was reset from 240 to 11000. I put 300 knots in the speed window. I then edited the speed on the VNAV descent page to 300 knots and edited the speed restrictions on the legs page at STNLE and CUUPP to 300. After executing these revisions I noticed the airplane began an uncommanded right turn off of the magenta line. At this point I hit heading select and slewed the heading cursor back around to re-intercept the magenta line. I now noticed that although the magenta line still went through BHAWK the fix itself had turned white and STNLE the next fix on the arrival had become active. I rearmed LNAV; but it did not capture as we flew back through the course; so I slewed the heading select back towards BHAWK. The airplane was slow to respond; so I disconnected the autopilot and was now hand flying to BHAWK. As we approached BHAWK ATC asked if we are still descending via the FYTTE 2. The co-pilot then said we need to cross BHAWK above 220 and informs me that I am already low and still descending. I leveled off and we crossed BHAWK below 220. In the confusion of losing the BHAWK fix and flying the aircraft back to the now white fix indication I had not realized that the FMC had lost the vertical crossing restrictions at BHAWK. After passing BHAWK the flight director recaptured the magenta line into STNLE and the VNAV path came back. I re-engaged the autopilot with no further problems.My opinion of the overall problem here is we do too much typing and not enough flying.

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.