Above two images are from the Scotch College commemorative website.
Scotch College moved it's WW1 Roll of Honour while I wasn't looking, but I have lately relocated it, now with articles about those who died, and those who won honours and awards. The above images come from a page about Australian Flying Corps Cadet George Robinson Johnston. Johnston initially embarked with the 6th Infantry Battalion, but later transferred to the Australian Flying Corps.
He met his death while still in training as an observer in a two seater aeroplane. Johnston's pal from the Flemington Presbyterian Church, Driver Reginald Robert McLean, wrote home that the pilot was thought to have fainted at the controls, and George had no way of controlling the aircraft from his seat behind.
The pictured cross made from an aeroplane propeller, perhaps even the one from the crashed aeroplane, was made by the mechanics in his unit, and placed over his grave at Winchester (West Hill) Old Cemetery.