Airco DH.4 Liberty The Airco DH.4 was a British two-seat biplane day bomber of the First World War. It was designed by Geoffrey de Havilland (hence “DH”) for Airco, and was the first British two-seat light day-bomber to have an effective defensive armament. The DH.4 was developed as a light two-seat combat aircraft, intended to perform both aerial reconnaissance and day bomber missions. One of the early aims of the design was for it to be powered by the newly-developed Beardmore Halford Pullinger (BHP) engine, capable of generating up to…