Arnold was confirmed in the rank of
Flight Sub-Lieutenant, effective from 1 August 1914, when he was assigned to
HMS Pembroke on 5 October 1914. He was granted aviators certificate No. 876 on 28 August 1914. He was promoted to
Flight Lieutenant on 31 December 1914. Arnold was elected to membership of the
Royal Aero Club on 5 October 1915. ==Aerial victories==