The first
prototype was completed in June 1915 however it wasn't until November that the first examples was handed over to the authorities for service evaluation when it was found to be underpowered and suffered from poor manoeuvrability and a low service ceiling, which precluded it from being used in its intended role as a bomber. While developing the aircraft, a number of crashes occurred of which the most disastrous for Caudron occurred on 12 December 1915, when
Gaston Caudron was killed while testing an early production aircraft. These crashes were found to be the result of structural deficiencies, which required substantial redesign, particularly of the center-section wing spars. This redesign work was carried out by
Henry Potez. While the brothers
Caudron had collaborated closely in aircraft design up to this point, the similar
G.5 and
G.6 were the work of Gaston Caudron, while the R.4 was by René Caudron. These were a radical departure from their increasingly obsolete predecessors, the
G.3 and
G.4, both of which were pod and boom designs, and were difficult to defend due to the positions of the crew. In contrast the R.4 had a streamlined, full-length
fuselage and single
fin and
rudder, and three cockpits, with gunners ahead and behind the wings, and the pilot just behind the wing. The unequal-span wings had three bays on each side of the strut-mounted engines, and were fitted with
ailerons on the upper wing only. As well as the twin-wheel main landing gear units and tailskid, the R.4 could be identified from other Caudrons by its single nose-wheel which was a common feature on French bombers and was intended to prevent nose-overs in the event of a rough landing. Its unimpressive climb rate and poor ceiling resulted in a few aircraft being tested with more powerful
Hispano-Suiza 8Aa engines. The new Caudron chief designer, Paul Deville, then set to work further refining the design. The result would be the
Caudron R.11. Development delays meant the first aircraft didn't reach the front lines until late 1916, so that only one example was in service at the start of October. ==Operational history==