My father had this flu in 1918. He was a soldier and was in New Jersey awaiting transport to Europe when he became ill. He survived but was unconscious for two weeks and never made it to Europe.
Many of you are probably not aware that there was an Encephalitis associated with the 1918 flu. The Encephalitis caused a condition commonly referred to as "sleeping sickness." My father was affected by this and would sometimes fall asleep for no apparent reason.
The Encephalitis was also recurrent and would sometimes recur in its most virulent form. This happened to him in 1946 and he died at the age of 56.
Sorry to hear about your dad.
Do you know if the encephalitis was from a separate microbe or was an effect of the flu?