After completing a masters degree in mechanical engineering and naval architecture at University College, London - where Colin Chapman studied - McDonald joined spent three years working with the Royal Corps of Naval Constructors, helping to design equipment for the Royal Navy and then joined the Brabham team in Chessington in 1985, his job being to design and build a one-third scale windtunnel for the team to use. When that was completed he moved into the drawing office and helped Sergio Rinland design the Brabham BT56 which was used in 1987. In 1988 the team withdrew from the World Championship and Rinland and his team worked on the design of a prototype Procar (the Brabham BT57) for Alfa Romeo. The team then returned to F1 under new ownership and McDonald was involved with the design of the BT58. That year he also race engineered Stefano Modena.