Butler came home to Australia about the 5th July, 1919, and a few weeks later his Bristol M.1C Monoplane (Red Devil), his Avro 504K Biplane and three 110 h.p. Le Rhone rotary engines which could be fitted to either plane arrived in the country under the care of Lt. H.A Kauper, R.F.C., Sergeant-Major Samuel Cecil Crawford and Leslie Jack Lucas.
Kauper, who was now associated with Butler, originally came from Melbourne. He was another aviation fanatic, and went to England in 1909 where he became a first-class aeronautical engineer and designer. Together with Harry Hawker (also destined to become famous) he won a Daily Mail prize for the first flight around Great Britain.
Kauper invented the gear which made it possible for British fighter pilots to fire through the revolving propellers of their planes – without hitting the propellers.
He was a brilliant engineer and Butler was fortunate to have his services during the brief life of their aviation company.
Later, Kauper was a co-worker in the invention of the radio transceivers that are used in the Royal Flying Doctor Service.
Jack Lucas was for a long time in the employ of Butler and Kauper as a mechanic and general utility man – he went with Butler on most of his mail-carrying trips.
Crawford was a lifelong friend who was himself interested in aviation from its earliest days, and was always on hand to give Harry encouragement and advice in peace and war. His name constantly recurs in connection with Butler’s activities from childhood until his early death, and his opinion was always greatly respected and usually acted upon.
By July 31st, 1919, just three weeks after his return from overseas, and eight days after the arrival of his planes, Harry Butler was giving exhibitions and displays of flying and stunting.