Narrative:

I had just returned to the flight deck from my break; which was the last break period. The relief pilot had left the cockpit and the captain was going to take a quick break upon his return. We were already in the initial descent which had been initiated by the captain. As I recall; we had been cleared to FL360. I was involved with finding the arrival pages and approach charts and was not paying attention to the progress of the descent. I noticed the aircraft making a significant roll to the right and looked to the map and determined we were deviating significantly to the right of the arrival path. At the same time the captain had gotten up to let the relief pilot back in. I said something to the effect of 'why are we turning off course?' I noted that LNAV was engaged and I disconnected the autoplt and began to correct back to the course. Simultaneously; the captain said 'watch your altitude.' I checked the altitude and we were about 400 ft low from FL360. I initiated a climb as we were still descending and climbed back to FL360. I was attempting to make the correction as smooth as possible but also as expeditious as possible while trying to pull as few G's as possible. As we started to level off at FL360 center called and questioned our altitude. By this time the relief pilot had sat down in the captain's seat and responded level at FL360. Center said their radar showed us 400 ft low. I responded to center that we had experienced an autoplt malfunction and were correcting the deviation. Their response was; 'that is good information to know'? Or words to that effect. When I noted the flight path deviation and assumed an autoplt malfunction; I was (during this process) thinking about a similar autoplt malfunction I experienced last month. We had a malfunction that required a diversion. The captain was flying and during the turn off course; heading select was chosen. Every time the captain turned right; the aircraft turned left. We experienced this several times before he chose to hand fly the aircraft. The malfunction was written up. As we progressed in the arrival; the purser advised us there were 5 injuries reported due to the flight path correction. I believe they said 3 passenger and 2 flight attendants were injured. The captain advised the purser that the deviation had likely been caused by a wake turbulence encounter. Coordination of this issue took place between the captain and the purser and I was not sure of any specific details of injuries but it seemed to be that ultimately the injuries were superficial. I was not aware of any further action in this regard. Human factors involved were that there was a fair amount of confusion in the cockpit involved in the crew changeover process and the deviation/malfunction could not have occurred at a more vulnerable point. Supplemental information from acn 787405: during initial stages of descent we were cleared to descend from FL390 to FL360. First officer was flying with autoplt engaged and in LNAV and VNAV. As we were descending through FL365 the aircraft made a rapid bank of 45 degrees to the right off course in approximately 15 seconds. There was no map shift occurring; updating was assured and I immediately checked FMA's to confirm mode of operation; verifying that LNAV and VNAV were engaged. The first officer voiced concern and confusion as to what was happening. Concurrently; the aircraft descended through the cleared FL360; at which time I yelled 'altitude' and 'disengage the autoplt and fly the aircraft.' the first officer responded quickly; avoiding the necessity of taking over control of the aircraft. The combination of correcting back left to the airway and arresting the descent resulted in pulling about 2 G's. We bottomed out at FL354 and corrected back to the cleared FL360. The ATC facility noted a deviation of 400 ft and asked reason for the deviation; to which the first officer responded 'an autoplt malfunction.' the ATC facility acknowledged the communication but did not ask for any other information or actions on our part. We were informed by the purser that 2 flight attendants and 1 passenger were knocked off their feet and sustained some amount of discomfort/injury. While no apparent causes were obvious; the 1 possible cause was a wake turbulence encounter; although inconclusive due to no TCAS visuals to confirm that conclusion.

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Original NASA ASRS Text

Title: B777 FO REPORTS AUTOPILOT MALFUNCTION AS CAPT AND RELIEF PILOT SWITCH POSITIONS DURING DESCENT; CAUSING ALT AND COURSE DEV WITH PAX INJURIES.

Narrative: I HAD JUST RETURNED TO THE FLT DECK FROM MY BREAK; WHICH WAS THE LAST BREAK PERIOD. THE RELIEF PLT HAD LEFT THE COCKPIT AND THE CAPT WAS GOING TO TAKE A QUICK BREAK UPON HIS RETURN. WE WERE ALREADY IN THE INITIAL DSCNT WHICH HAD BEEN INITIATED BY THE CAPT. AS I RECALL; WE HAD BEEN CLRED TO FL360. I WAS INVOLVED WITH FINDING THE ARR PAGES AND APCH CHARTS AND WAS NOT PAYING ATTN TO THE PROGRESS OF THE DSCNT. I NOTICED THE ACFT MAKING A SIGNIFICANT ROLL TO THE R AND LOOKED TO THE MAP AND DETERMINED WE WERE DEVIATING SIGNIFICANTLY TO THE R OF THE ARR PATH. AT THE SAME TIME THE CAPT HAD GOTTEN UP TO LET THE RELIEF PLT BACK IN. I SAID SOMETHING TO THE EFFECT OF 'WHY ARE WE TURNING OFF COURSE?' I NOTED THAT LNAV WAS ENGAGED AND I DISCONNECTED THE AUTOPLT AND BEGAN TO CORRECT BACK TO THE COURSE. SIMULTANEOUSLY; THE CAPT SAID 'WATCH YOUR ALT.' I CHKED THE ALT AND WE WERE ABOUT 400 FT LOW FROM FL360. I INITIATED A CLB AS WE WERE STILL DSNDING AND CLBED BACK TO FL360. I WAS ATTEMPTING TO MAKE THE CORRECTION AS SMOOTH AS POSSIBLE BUT ALSO AS EXPEDITIOUS AS POSSIBLE WHILE TRYING TO PULL AS FEW G'S AS POSSIBLE. AS WE STARTED TO LEVEL OFF AT FL360 CTR CALLED AND QUESTIONED OUR ALT. BY THIS TIME THE RELIEF PLT HAD SAT DOWN IN THE CAPT'S SEAT AND RESPONDED LEVEL AT FL360. CTR SAID THEIR RADAR SHOWED US 400 FT LOW. I RESPONDED TO CTR THAT WE HAD EXPERIENCED AN AUTOPLT MALFUNCTION AND WERE CORRECTING THE DEV. THEIR RESPONSE WAS; 'THAT IS GOOD INFO TO KNOW'? OR WORDS TO THAT EFFECT. WHEN I NOTED THE FLT PATH DEV AND ASSUMED AN AUTOPLT MALFUNCTION; I WAS (DURING THIS PROCESS) THINKING ABOUT A SIMILAR AUTOPLT MALFUNCTION I EXPERIENCED LAST MONTH. WE HAD A MALFUNCTION THAT REQUIRED A DIVERSION. THE CAPT WAS FLYING AND DURING THE TURN OFF COURSE; HDG SELECT WAS CHOSEN. EVERY TIME THE CAPT TURNED R; THE ACFT TURNED L. WE EXPERIENCED THIS SEVERAL TIMES BEFORE HE CHOSE TO HAND FLY THE ACFT. THE MALFUNCTION WAS WRITTEN UP. AS WE PROGRESSED IN THE ARR; THE PURSER ADVISED US THERE WERE 5 INJURIES RPTED DUE TO THE FLT PATH CORRECTION. I BELIEVE THEY SAID 3 PAX AND 2 FLT ATTENDANTS WERE INJURED. THE CAPT ADVISED THE PURSER THAT THE DEV HAD LIKELY BEEN CAUSED BY A WAKE TURB ENCOUNTER. COORD OF THIS ISSUE TOOK PLACE BTWN THE CAPT AND THE PURSER AND I WAS NOT SURE OF ANY SPECIFIC DETAILS OF INJURIES BUT IT SEEMED TO BE THAT ULTIMATELY THE INJURIES WERE SUPERFICIAL. I WAS NOT AWARE OF ANY FURTHER ACTION IN THIS REGARD. HUMAN FACTORS INVOLVED WERE THAT THERE WAS A FAIR AMOUNT OF CONFUSION IN THE COCKPIT INVOLVED IN THE CREW CHANGEOVER PROCESS AND THE DEV/MALFUNCTION COULD NOT HAVE OCCURRED AT A MORE VULNERABLE POINT. SUPPLEMENTAL INFO FROM ACN 787405: DURING INITIAL STAGES OF DSCNT WE WERE CLRED TO DSND FROM FL390 TO FL360. FO WAS FLYING WITH AUTOPLT ENGAGED AND IN LNAV AND VNAV. AS WE WERE DSNDING THROUGH FL365 THE ACFT MADE A RAPID BANK OF 45 DEGS TO THE R OFF COURSE IN APPROX 15 SECONDS. THERE WAS NO MAP SHIFT OCCURRING; UPDATING WAS ASSURED AND I IMMEDIATELY CHKED FMA'S TO CONFIRM MODE OF OP; VERIFYING THAT LNAV AND VNAV WERE ENGAGED. THE FO VOICED CONCERN AND CONFUSION AS TO WHAT WAS HAPPENING. CONCURRENTLY; THE ACFT DSNDED THROUGH THE CLRED FL360; AT WHICH TIME I YELLED 'ALT' AND 'DISENGAGE THE AUTOPLT AND FLY THE ACFT.' THE FO RESPONDED QUICKLY; AVOIDING THE NECESSITY OF TAKING OVER CTL OF THE ACFT. THE COMBINATION OF CORRECTING BACK L TO THE AIRWAY AND ARRESTING THE DSCNT RESULTED IN PULLING ABOUT 2 G'S. WE BOTTOMED OUT AT FL354 AND CORRECTED BACK TO THE CLRED FL360. THE ATC FACILITY NOTED A DEV OF 400 FT AND ASKED REASON FOR THE DEV; TO WHICH THE FO RESPONDED 'AN AUTOPLT MALFUNCTION.' THE ATC FACILITY ACKNOWLEDGED THE COM BUT DID NOT ASK FOR ANY OTHER INFO OR ACTIONS ON OUR PART. WE WERE INFORMED BY THE PURSER THAT 2 FLT ATTENDANTS AND 1 PAX WERE KNOCKED OFF THEIR FEET AND SUSTAINED SOME AMOUNT OF DISCOMFORT/INJURY. WHILE NO APPARENT CAUSES WERE OBVIOUS; THE 1 POSSIBLE CAUSE WAS A WAKE TURB ENCOUNTER; ALTHOUGH INCONCLUSIVE DUE TO NO TCAS VISUALS TO CONFIRM THAT CONCLUSION.

Data retrieved from NASA's ASRS site as of May 2009 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.