B777-200
Fatigue; Situational Awareness; Workload
Deviation - Track / Heading All Types; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Flight Crew Became Reoriented
Human Factors
This is an event that you see in Human Factors class and wonder how it happened and hope it doesn't happen to you. We were on the arrival with [a transition] to the ILS.... I was on path at 240 KTS when APPROACH slowed us to 170 KTS. I set the speed select to 170 KTS and added speed brakes. The aircraft was slowing very slowly due to the angle of descent on that segment. The First Officer (FO) wondered if I wanted the Gear down but I decided not to lower the gear since we were above 200 KTS. B777 VOL 1 (CLIMB-CRUISE-DESCENT says; 'Avoid using the gear for drag above 200KTS').My thought was to disconnect the autopilot; raise the nose to slow then recapture the path. There went one important layer of protection and my workload doubled. I was using LNAV/VNAV until inside [waypoint X] to ensure that the crossing restrictions were met. We were then told to slow to final approach speed. I started to fixate on slowing and let the aircraft drift to the left of course. The FO brought this to my attention. I started to head back to the path but in doing so I let the nose of the aircraft [drop]; increasing the rate of descent. We got one cycle of TERRAIN TERRAIN. The FO called for me to pull the nose up which I was in the process of doing. During this event we were in DAY VMC conditions. I armed the APPROACH and intercepted the LOC and GS. Since we were in VMC conditions; I continued with a normal; stable approach to landing. If it had been IMC I would have gone around at losing the course.Fatigue probably played some in this event. I followed my normal routine prior to the flight but we experienced light to moderate chop for nearly all our flight. This reduced the quality of rest during my break.This was my first time flying this arrival and approach...in about 5 years. I briefed the approach and terrain but should have realized that slowing on the final segments of the arrival would be difficult.Why would I disconnect the autopilot? I immediately increased the workload for myself and the FO and [relief pilot]. If I had wanted to raise the nose to slow I should have used vertical speed with the autopilot connected and then intercept the glideslope from above per the procedure in the B777 manual. Why I would disconnect the autopilot in a high workload situation still baffles me.Check the descent rates required between fixes. Request that anything that the FO and [relief pilot] see that is not standard or abnormal to call it out loudly and don't assume I'm correcting. It takes a louder than normal voice sometimes to break through the concentration the Pilot Flying is using to register what is being said.
Approaching LOM we're going below GS and still left of LOC. ATC hand-off to Tower occurs about the same time as the call for GEAR-DOWN; adding some distraction/confusion. Now we're at least a dot low of GS. I call 'PULL THE NOSE UP'. I can see the ground. I notice we're at about 1;400 feet MSL just inside the LOM. GPWS sounds 'TERRAIN; PULL-UP'. Ground and runway now in view. Captain levels off; corrects back to LOC; and captures GS. We're fully configured and stable on the approach by 1;000 feet AGL.
A B777-200 Captain attributed track and altitude deviations on approach to the procedures used in attempting to slow the aircraft.