[2] In March 1916 Caddell was appointed Deputy Assistant Director of Military Aeronautics at the War Office in London.
He effectively served as the chief assistant to Brigadier-General Duncan MacInnes, the Director of Aircraft Equipment.
[3] It was in that capacity that he was introduced to George Constantinescu who had developed an experimental synchronization gear.
[4] With support from the Military Aeronautics Directorate, Constantinescu's synchronization gear was improved and deployed on aircraft in France.
[6] In April 1917 Caddell took over from an overworked and exhausted MacInnes as Director of Aircraft Equipment.