Caudron G . 4 The Caudron G . 4 was a French biplane with twin engines , widely used during World War I as a bomber aircraft . It was designed by René and Gaston Caudron as an improvement over their Caudron G . 3 . The aircraft employed wing warping for banking . The first G . 4 was manufactured in 1915 , both in France , England and in Italy . The Caudron G . 4 was used as a reconnaissance bomber into the heart of Germany . Later , when Germany developed a fighter force , the aircraft had to be used for night bombings . The G . 4 was in use in Belgium , France , Finland , Italy , the United Kingdom , and the United States . Development . While the Caudron G . 3 was a reliable reconnaissance aircraft , it could not carry a useful bombload , and owing to its design , was difficult to fit with useful defensive armament . In order to solve these problems , the Caudron G4 was designed as a twin engined development of the G . 3 , first flying in March 1915 . While the G . 4 had a similar pod and boom layout to the G . 3 , it has two Le Rhône rotary or Anzani 10 radial engines mounted on struts between the wings instead of a single similar engine at the front of the crew nacelle , while wingspan was increased and the tailplane had four rudders instead of two . This allowed an observer / gunner position to be fitted in the nose of the nacelle , while the additional power allowed it to carry a bombload of 100 kg . A total of 1358 G . 4s were produced in France , while a further 51 examples produced by the A . E . R . company in Italy and 12 were built in Britain by the British Caudron company . Operational history . World War I . The G . 4 entered service with the French Aéronautique Militaire in November 1915 . It was the first twin engined aircraft in service in any numbers with the French . The Caudron G . 4 was used to carry out bombing raids deep behind the front line , being used to attack targets as far away as the Rhineland . Increasing losses led to its withdrawal from day bombing missions by the French in the autumn of 1916 . The British Royal Naval Air Service ( RNAS ) also used the G . 4 as a bomber , receiving 55 , of which twelve were licence built by the British Caudron company and the remainder supplied from France . Number 4 and 5 Wing RNAS using the G . 4 for attacks against German seaplane and airship bases in Belgium . It was finally replaced in RNAS service by Handley Page O / 100 aircraft in the autumn of 1917 . Italian G . 4s proved successful in operating in the mountainous Alpine fronts , where its good altitude capabilities proved useful . The G . 4 was also used by the Imperial Russian Air Force for reconnaissance purposes . Use in Finland . The Finnish Air Force purchased one G . 4 as well as two G . 3s aircraft with spares , from Flyg Aktiebolaget on April 26 , 1923 for 100 , 000 Finnish markka . The G . 4 was used by the FAF as an ambulance aircraft in 1923 . Variants . The first G . 4 prototype flew in March 1915 . The G . 4 was manufactured in three main versions , A2 for reconnaissance , B2 for bombing and E2 for training . The A2 was equipped with a radio for fire spotting , B2 could carry 100 kg of bombs and the E2 was equipped with dual controls . G . 4IB ( French : " Blindage " ) was an armoured version . There were also other bomber and escort aircraft versions . The Caudron G . 6 was a further developed G . 4 , with a conventional fuselage and tail replacing the pod and boom arrangement of the G . 3 .