The Airco D.H.11 Oxford was designed as a potential replacement for the D.H.10 twin-engined day bomber, but never progressed beyond the prototype stage.
The D.H.11 was a very different design to the D.H.10. On the earlier aircraft fuselage was attached to the lower wing, and the engines were mounted between the wings. On the D.H.11 the fuselage filled the gap between the upper and lower wings, and the engines were attached to the lower wings. The two wings also had a slight dihedral – four degrees on the upper wing and two degrees on the lower, so the gap between the wings got visibly larger towards the end.
The D.H.11 carried a crew of three. The front gunner and pilot were in a conventional position in front of the wings, while the rear gunner was in a mid-upper position, just behind the trailing edge of the upper wing. This gave the rear gunner a better than normal field of view, although did leave the aircraft vulnerable to attacks from below and behind. The larger fuselage also meant that there was room for the rear gunner to reach the pilot's cockpit if needed. The D.H.11 was armed with two 0.303in Lewis guns, mounted on Scarff rings in the front and mid-upper positions, and could carry up to four 230lb bombs internally.
As was so often the case in this period, problems with it engines slowed down the development of the D.H.11. It was designed around two 320hp A.B.C. Dragonfly radial engines, but these turned out to be heavier and less powerful than expected. Work was suspended for a period from September 1918, and some work was done on using a pair of 300hp Siddeley Puma engines in an Oxford Mk.II.
The single prototype to be completed made its maiden flight in January 1919, powered by the Dragonfly engines. Early tests revealed that it was nose-heavy and unstable in flight, but flight tests ended after a connecting rod broke in one of the engines soon after a take off. The aircraft was returned to the Airco factory for repairs and modifications, but these were never completed. The RAF suffered from very heavy budget cuts after the end of the First World War. The plan to replace the D.H.10 was abandoned, and with it any further work on the D.H.11.
Engine: Two A.B.C. Dragonflies
Power: 320hp each
Wing span: 60ft 2in
Length: 45ft 2.75in
Height: 13ft 6in
Tare Weight: 3,795lb
All-up weight: 7,027lb
Max Speed: 117mph at 6,500ft
Endurance: 3hr 15im
Armament: Front and rear Lewis guns