Complex sentence: During the Second World War, he flew more than five hundred operational sorties, He spent several months as a Hawker experimental test pilot developing the Hawker Typhoon and Tempest, and was responsible for introducing these types into operational squadron service.
Split into simpler sentences: During the Second World War, he flew more than five hundred operational sorties. He also spent several months as a Hawker experimental test pilot developing the Hawker Typhoon and Tempest, and was responsible for introducing these types into operational squadron service.