The pilot to whom you refer was Lewis Strange, who was one of the pioneers in arming his aircraft with a machinegun. On 10 May 1915, Strange attempted to attack an Aviatik while flying a Martinsyde scout with an over-the-wing Lewis gun. The empty drum of the Lewis became stuck in place, so Strange stood up in the cockpit and tried to wrestle the empty drum free. His ship stalled, rolled inverted, and Strange ended up dangling from the drum which only moments earlier he had been trying to free. This episode has been recorded in a number of references, but the original telling of the tale was in
Recollections of an Airman by Lewis A. Strange.