Few aircraft companies in Britain could claim to embrace the triplane arrangement as enthusiastically as Sopwith. While it would be building legendary biplane fighters such as the great Sopwith Camel that the company would be remembered for, it had enjoyed some moderate success with its aptly named Sopwith Triplane fighter which served with the Royal Naval Air Service’s “Black Flight”. Within three months of entering combat the flight had downed 87 German aircraft and the performance of the Triplane was such that it sparked off 1917’s triplane craze in Germany that ultimately led to the famed Fokker Dr.I.
The Sopwith Triplane didn’t catch on as well as hoped with British forces however and only 147 airframes were built, a comparatively small number for the time. Neither did it attract the hoped-for foreign interest although French, Greek and even Russian forces trialled the aircraft; in the latter case at least one example made its way in to the ranks of the embryonic Red Air Force post-revolution.
While Sopwith would primarily focus on biplanes, they continued to push for research in to triplanes to meet Royal Flying Corps and Royal Naval Air Service requirements. In 1916, after the RFC issued a requirement for a long-range escort fighter and airship-destroyer, the company began work on another relatively large triplane in response. The resulting aircraft, the rather mechanically-named Sopwith Long Range Tractor Triplane (LRTTr), was a three-bay, narrow chord wing design that featured a streamlined nacelle in the middle of the top wing for a gunner to be positioned. The Sopwith LRTTr was an extremely clumsy aircraft in the sky and by the time of its first flight was already rendered obsolete by the introduction of more capable biplane designs featuring synchronised machine guns that negated the need for the upper wing nacelle.
Only the prototype Sopwith LRTTr (right) was built but Sopwith were not dissuaded by this lack of success. On the contrary, they were still so enamoured with the triplane layout that they actually began drawing up a new triplane without there being an actual requirement having been issued by the RFC or RNAS. This time however the aircraft was to be wholly different beast being tailored for the bombing role rather than as a fighter. Experience gained on their previous efforts were put to good use in this new design and the aircraft featured only a single bay within its triplane wings which gave the aircraft a more advanced look to it.
It was intended for the aircraft to carry its offensive armament internally in an effort to streamline the design and so the fuselage was deepened to feature a small bomb bay under the pilot’s seat. It was intended that the aircraft would be armed with 450lbs of bombs that would be first fitted on to a self-contained pack which would then be loaded in to the aircraft. The pilot would be given a forward-firing .303 Vickers machine gun synchronised with the propeller while a defensive gunner had a .303 Lewis machine gun in the rear cockpit.
Sopwith approached the British authorities with their new proposal but were met with opposition since they were working on an aircraft that hadn’t been requested. Nevertheless, the design sufficiently impressed them to grant Sopwith a license to build two prototypes for testing as a private venture. There was in fact reason for Sopwith to be optimistic. After German Gotha bombers began attacking London, the British War Office recommended doubling the size of the RFC with the great majority of new squadrons being equipped with bombers. Airco’s DH.9 looked set to swallow up most of the orders but if Sopwith could prove their new aircraft superior then they might be able to tender it as a replacement in the following year.
Construction of the prototypes began in mid-1917 and the first Sopwith 2B2 Rhino was completed in October before being test flown from Brooklands. Driving the Rhino’s two-bladed propeller was a 230hp Beardmore Halford Pullinger in-line, water-cooled engine; an aeroengine that was widely available at the time and that had powered the prototype DH.9. The engine was mounted ahead and above of the weapon bay with the fuselage curving up toward it the look of which helped inspire the Rhino name. Unfortunately, this engine and its installation would lead to criticism from observers since it was proving unsatisfactory in the DH.9 with poor performance at altitude while its position on the Rhino made the aircraft very nose heavy making it something of a handful to land safely.
The first prototype (above) was nevertheless submitted for official testing in February 1918 which was undertaken at Martlesham Heath. It was joined by the second prototype the following month which was nearly identical except that the simple pillar mounting for the rear gunner was replaced by a more modern scarff ring. Unfortunately, the aircraft proved disappointing. Compared to the similarly powered DH.9, the Rhino was 10mph slower and had a significantly lower rate of climb both of which was of great concern to the RFC who were already unhappy with the speed of the early DH.9s they were receiving. Official figures showed that the Rhino had less endurance than the DH.9 and had a marginally smaller bombload.
Sopwith knew any effort to develop the design would be fruitless since 1917’s triplane craze which it had largely helped create was now well and truly over. While it was true that triplanes had the advantage of being able to use shorter span wings than an equivalent biplane which made them smaller targets in the air than an equivalent DH.9, the trade-off however was that they were often heavier than their biplane counterparts and they incurred far more drag. They were also prone to cross wind interference which was especially dangerous on landing. As the air war dragged on over the trenches it became increasingly obvious that speed was going to be the deciding factor and the newer biplanes were leaving triplanes behind. Sopwith would continue to dabble in triplane designs up until the end with their last aircraft, the Sopwith Snark, being developed in both biplane and triplane forms.
The two Rhino prototypes would be returned to Sopwith where they would have a short career testing new propeller designs before they were disposed of to join the list of British aviation oddities of World War I.