McCarthy was born in St. James, New York, a town on Long Island east of New York City, and grew up in Brooklyn. As a teenager, he worked as a lifeguard at Coney Island and learned to fly. In May 1941, months before the United States would enter the war, McCarthy joined the Royal Canadian Air Force.
World War II
McCarthy was best known for flying with No. 617 Squadron RAF, including the Dams Raid in 1943. By the time of the raid he had already taken part in thirty bombing sorties over Germany, including three over Berlin. McCarthy and his crew flew with the second wave of Lancasters, but he had to take a spare aircraft after his failed. T-Tommy was the only aircraft of the second wave to attack a target – the Sorpe Dam, which had to be attacked with an Upkeep bomb directly without it bouncing. Despite the bomb hitting the target, the dam was not breached.
Upon the conclusion of World War II, he remained in Farnborough and served with the Foreign Aircraft Flight for several more months, testing and evaluating several dozen ex-Luftwaffe aircraft types including the Arado Ar 232, Dornier Do 335, Focke-Wulf Fw 190 and Fw 200 Condor, and the Heinkel He 219. His first experience of a jet aircraft also took place at Farnborough, where he flight-tested a prototype Mk.4 Gloster Meteor.[4]
After departing the United Kingdom at the end of 1945, McCarthy returned to Canada and obtained his Canadian citizenship the following year.