McDonald was born in South Africa and grew up in St Kitts and Antigua. Later he obtained an Engineering degree at Peterhouse, Cambridge, and in 1924 joined the RAF. After a routine peacetime career his critical appointment came in 1937.
When Sir Henry Tizard and his colleagues first demonstrated the potentialities of radar (or Radio Direction Finding as it was then called), there were many who remained to be convinced of its practical application to air defence - and indeed of the real validity of any air defence ("The bomber will always get through," Stanley Baldwin, among others, was quoted as saying). Among those who maintained faith in its practicality was Lord Swinton, the far-seeing Air Minister.
On the airfield at Biggin Hill there was established an experimental flight of fighters designed to assess the merits, not only of radar, but of the whole concept of ground command and control, of which Air Chief Marshal Hugh Dowding, the recently appointed Commander-in-Chief of Fighter Command, was such a fervent advocate. Swinton told McDonald at the time of the experiments: "I hope you realise that the whole future of this country depends on the results which you obtain at Biggin Hill."
The results produced convinced even the most sceptical of observers. The vital radar stations, command and control installations and a barely adequate number of modern fighter aircraft were provided in the nick of time before the outbreak of the Second World War. For his contribution to that success McDonald was awarded the Air Force Cross.
He repeated that success in 1941 with the so-called Duxford flare path. At the time enemy intruder aircraft were proving a real menace to our night- flying operations owing to the intensity of airfield lighting which such operations demanded. McDonald's Duxford flare path was so cleverly designed as to be invisible to the enemy, so much so that during its use only one aircraft was shot down when landing at Duxford, and that because the pilot, a visitor, insisted on using the normal landing lights.
Unusually McDonald combined high technical ability with a real gift for dealing with human beings at all levels. Not only was he eventually to become Air Member for Personnel in the Air Council but he was popular and respected in a number of service appointments mixing with international organisations and people. These included being AOC of Training at air headquarters India and Commander-in-Chief of the fledgling Pakistani Air Force. He won a great reputation for understanding, managing and encouraging some of the best people involved in the formative years of several air forces; and for fairness and integrity in the Royal Air Force.
Outside the Service his overriding interest was in sailing, where he excelled both in administration and personal performance. He founded the renowned Seletar Yacht Club in Singapore and later helped to start the Royal Air Force Sailing Association on the Welsh Harp; both clubs being for all ranks. He raced 12ft dinghies with the Ranelagh Sailing Club and later X-boats with the Royal Lymington Yacht Club, winning his last race when over 90 years old. His wife, and the mother of his four children, served as his skilled and enthusiastic crew throughout his sailing career. He represented Great Britain in the Firefly single-handed class at the 1948 Olympic Games, in which he was the oldest competitor and so took the Olympic oath at the opening ceremony.
Arthur McDonald lived his long life in challenging times. He met all the challenges that came his way.
Arthur William Baynes McDonald, air force officer: born 14 June 1903; AFC 1938; CB 1949, KCB 1958; Commander-in-Chief, Royal Pakistan Air Force 1955-57; married 1928 Mary Gray (two sons, two daughters); died 26 July 1996.