Royal Air Force Uniform

The uniform that my grandfather was wearing was identified as:

It's a standard RAF issue Sidcot Suit (from the inventor, Australian RNAS aviator Flight Sub Lieutenant Sidney Cotton) made from proofed khaki twill over a rubberized muslin inter-lining and a mohair liner.  However, he may not have been going to fly in the immediate future, as he's wearing ordinary shoes, rather than an airman's fur-lined 'fug' boots, though sometimes airmen flew without the boots if the flight was to be short and/or at low level.

It seems strange that a man that served in the RFA since 1907 ended his career in the RAF. He remained in the RFA even-though he was sent to the RAF from Jan 1, 1918 to 1919. 

Still Learning

My grandfather's story continues to unfold as I learn more about his English heritage. Just recently I made contact with second cousins in the UK and they are supplying me with new information. them sent me three photos of my grandfather.
One showed him in what appeared to be a flying suit. Through the Great War Forum I was informed that the suit was a standard RAF issue Sidcot Suit (from the inventor, Australian RNAS aviator Flight Sub Lieutenant Sidney Cotton) made from proofed khaki twill over a rubberized muslin inter-lining and a mohair liner.  However, he may not have been going to fly in the immediate future, as he's wearing ordinary shoes, rather than an airman's fur-lined 'fug' boots, though sometimes airmen flew without the boots if the flight was to be short and/or at low level.