Page 92 Robert tells about his flight and problems. He was at 12,500 ft and his wife and son fell asleep and his own mind was a bit slow and confused. Then he had his carburetor ice up on decent. In his summary of what he learnt Roberts tells about the most potent lesson (p.95) which all related to his continued efforts to solve the engine problem. No doubt all this was his prime problem, but did he really understand that a continued flight above FL100 without oxygen caused the pax to sleep and no doubt slowed his brains considerable. Do any of you fly without oxygen above FL100?