Gavin was Chairman of the Air Command Board for 3 years during which he led the transformation of the Board and its supporting headquarters from a place of bureaucratic comfort, to a leading strategically driven organisation respected for its role in supporting capability generation. As Deputy Chief of Air Force, he controlled acquisition, sustainment and personnel management systems for the future force and represented Air Force in Enterprise level fora. He directed the Air Force transformation and innovation team (JERICHO) to success in connecting Air Force with academia and fostering the rapid development of world leading technologies in support of the Joint Force.

He was appointed A Member of the Order of Australia (AM) in 2016; and is a recipient of the Commendation for distinguished service and the United States Air Force Bronze Star. He has a Graduate Certificate in Management (QUT), is a Graduate of the Australian Institute of Company Directors Course (GAICD), and a graduate of Stanford-NUS Executive Program in International Management.

AVM Turnbull has been appointed as an Operational Member of the Defence Airworthiness Board panel and retains a current TS (PV) security clearance. He was appointed Chairman of the Public Sector Advisory Board in 2020.