Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 130; Flight Crew Total 14000; Flight Crew Type 1200
No Specific Anomaly Occurred All Types
Human Factors
I entered the cockpit after my rest break.  The Captain stepped back for a bathroom break.  The copilot was alert; however; he shut his eyes and then his head tilted down.  When the Captain returned after a few minutes; it was copilot's turn to take a rest break.  He took several minutes to arise.  I called his name; pushed on his shoulder; then pulled back his chair.  He arose and went back for his rest break seeming groggy.  Because he took longer than normal to arise; and would now be in the back; out of sight and alone for two hours on his break; we wanted to confirm that nothing medically wrong had occurred.  The Captain talked to Dispatch then Medlink; then solicited the help of a doctor in first class.  He was examined and passed all tests for alertness; understanding; reactions; blood pressure; etc.  This was done within about 15 minutes of the initial occurrence.  He occupied the jumpseat after his rest break and for the landing; only as a precaution.  For the duration of the flight he appeared normal in every way and performed pilot duties normally.
Just before leaving the cockpit for my previously-scheduled rest break; I dozed off unintentionally; and was apparently very difficult to awaken.  Once awake; I went to the forward galley and chatted with the Flight Attendant; asked for a snack if one was available; then went to the sleeper seat.  I ate my food at a leisurely pace; popped in some earplugs and turned out the lights to take some sleep.  Shortly thereafter I was awakened by the purser; who was in the company of a medical doctor.  The doctor had been asked by the Captain to perform an evaluation of my condition; and it appears from her report that I was just fine.  Which is exactly how I felt.  I returned to the cockpit later to take over the duties of relief pilot.
A B777 Relief Pilot reported that as she is about to relieve the flying First Officer; he nods off and was very difficult to awaken.  As a precaution the Captain had the First Officer examined by an on board physician and the relief pilot assume the First Officer's position.