Narrative:

We were flying a B767 aircraft; which is one of the aircraft that locks in V/south in the takeoff mode when the autopilot is selected at 500 ft (a requirement for RNAV sids). I briefed the procedure for dealing with this condition during the before start checklist to both the first officer and the relief officer. Neither of them had flown one of these planes before using the new RNAV procedure (autopilot at 500 ft). We came in 5000 pounds light at closeout and probably would have been just able to use reduced thrust; but I elected to go with maximum power and original speeds; as there was a 1-2 knot tailwind on the ATIS. I engaged LNAV at approximately 500 ft and the autopilot soon thereafter at approximately 700 ft. I immediately checked the vertical speed window and saw it open as advertised in the warning notice and was surprised to see 3300 FPM. I began to slowly crank the vertical speed down so as not so as not to upset the passengers; but it became obvious that a more aggressive nose command was required. I was about to disconnect the autopilot when it became clear the autopilot was recovering nicely. When the speed increased and going through approximately 1700 ft; I engaged VNAV and the rest of the climb was normal. During the recovery from the autopilot high vertical speed lock our airspeed decreased to just above V1. There was no danger of a stall as the airplane was unloaded and pitching over to gain speed. I asked both the first officer and relief officer if they had seen what had happened and both of them said no! The first officer was talking to departure control; a requirement in eddf after takeoff; and the relief officer was probably blocked by my arm across my instruments adjusting the vertical speed. The procedure; especially in the aircraft that have this software flaw; is an accident waiting to happen. There is no doubt in my mind that without corrective action on my part the aircraft would have entered a deep stall possibly unrecoverable at that altitude. This happened to me in perfect weather conditions and despite my 15 years experience as a captain on the B767. Couple this occurrence with bad weather; windshear; inexperienced crew; minor inattention; etc.; and it isn't hard to see the danger. We need to stop this procedure now! One hundred RNAV departure violations are better than one accident caused by an ill-conceived RNAV accuracy procedure.

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Original NASA ASRS Text

Title: B767 Captain reports that his carriers procedure for flying RNAV departures in certain aircraft with upgraded FMC's causes an unsustainable vertical speed to be captured when autopilot is first engaged; requiring prompt pilot action to prevent a stall.

Narrative: We were flying a B767 aircraft; which is one of the aircraft that locks in V/S in the takeoff mode when the autopilot is selected at 500 FT (a requirement for RNAV SIDS). I briefed the procedure for dealing with this condition during the before start checklist to both the First Officer and the Relief Officer. Neither of them had flown one of these planes before using the new RNAV procedure (autopilot at 500 FT). We came in 5000 LBS light at closeout and probably would have been just able to use reduced thrust; but I elected to go with maximum power and original speeds; as there was a 1-2 knot tailwind on the ATIS. I engaged LNAV at approximately 500 FT and the autopilot soon thereafter at approximately 700 FT. I immediately checked the vertical speed window and saw it open as advertised in the warning notice and was surprised to see 3300 FPM. I began to slowly crank the vertical speed down so as not so as not to upset the passengers; but it became obvious that a more aggressive nose command was required. I was about to disconnect the autopilot when it became clear the autopilot was recovering nicely. When the speed increased and going through approximately 1700 FT; I engaged VNAV and the rest of the climb was normal. During the recovery from the autopilot high vertical speed lock our airspeed decreased to just above V1. There was no danger of a stall as the airplane was unloaded and pitching over to gain speed. I asked both the First Officer and Relief Officer if they had seen what had happened and both of them said no! The First Officer was talking to Departure Control; a requirement in EDDF after takeoff; and the Relief Officer was probably blocked by my arm across my instruments adjusting the vertical speed. The procedure; especially in the aircraft that have this software flaw; is an accident waiting to happen. There is no doubt in my mind that without corrective action on my part the aircraft would have entered a deep stall possibly unrecoverable at that altitude. This happened to me in perfect weather conditions and despite my 15 years experience as a Captain on the B767. Couple this occurrence with bad weather; windshear; inexperienced crew; minor inattention; etc.; and it isn't hard to see the danger. We need to stop this procedure now! One hundred RNAV departure violations are better than one accident caused by an ill-conceived RNAV accuracy procedure.

Data retrieved from NASA's ASRS site as of April 2012 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.