The de Havilland DH.111 was something of an in-direct proposal against Air Ministry Specification B.35/46, the same requirement that went on to produce the classic "V-bomber" trio of nuclear-capable bombers for the Royal Air Force (RAF) - the trio being made up of the Avro "Vulcan", the Handley Page "Victor", and the Vickers "Valliant" (all detailed elsewhere on this site). de Havilland offered the Air Ministry a modified, militarized version of its soon-to-be DH.106 "Comet" narrow-body passenger jet airliner which took to the skies for the first time on July 27th, 1949. In its civilian-minded form, it entered service with BOAC in May of 1952 and production reached 114 units (including the project prototypes).
Under this existing framework, it was reasoned to provide the RAF with a bombing platform in the shortest amount of time when compared to competing designs. Technologies and design qualities would all be proven by flying the DH.106 instead of designing and building an advanced bomber form from scratch. The design work on the new aircraft was readied for official review in May of 1948 and it became known officially as the "PR Comet" and unofficially as the "Comet Bomber".
Based on the production "Comet 1" airliner, the DH.111 was to retain as many of the physical qualities of the original jet as possible, including its four turbojet engine arrangement- to expedite development. The fuselage was redrawn with slimmer lines which reduced frontal drag and lightened overall weight. The aircraft was also given additional internal fuel stores to help increase the design's estimated operational range - a critical quality of Cold War-era bombers. Pressurization would be had at all of the crew spaces - four crewmen would be used to operate the machine as opposed to the Specification's required five personnel.
The wing mainplanes kept their original design lines but the members were raised to the mid-mounted position along the sides of the fuselage (the original Comet held its mainplanes low against the fuselage). The members were used to house the paired turbojet engines at the wing roots, two engines to a wing. The engines were aspirating from oval ports at the leading edges and exhausted through circular ports at the trailing edges. Sweep back was noted at the leading edges with only slight sweep back given to the outboard section of the trailing edges. All pertinent trailing edge control surfaces were present outboard of the engine exhaust ports.
The hollow nose section would be home to the H2S Mk.IX series airborne, ground-scanning radar system. However, the sheer size of this unit within the confines of the Comet's fuselage required that nose section be reworked to include cheek "blisters" to better accommodate the system's width. The cockpit was positioned over and aft of the nose cone and identified by a framed, "bubble-style" canopy seated high on the design. The tubular fuselage then ran towards the rear of the aircraft, tapering elegantly at the tail section. The tail unit encompassed a single vertical fin with upward-canted horizontal planes, these members installed at the fin's base. Ground-running would be done with a conventional (wholly retractable) tricycle undercarriage utilizing a double-wheeled nose leg and single-wheeled main landing gear legs. The nose leg retracted under the cockpit while the main legs were set just outboard of the outer-most turbojet engine installation at the wings. As drawn up, the DH.111 was given a running length of 95 feet and a wing span of 115 feet while gross weight reached 105,000lb.
Propulsion power would come from 4 x de Havilland "Ghost" air-breathing turbojet engines of 5,700lb of thrust each unit. Engineers estimated their aircraft to have a maximum speed of 518 miles-per-hour while reaching an altitude of 50,000 feet out to a range of 4,280 miles.
Internally, it was proposed that the bomber would carry up to 18 x 1,000lb conventional drop bombs or 1 x 10,000lb nuclear-tipped ordnance in their place. However, there arose concern amongst British authorities that the bomb bay could not quite accommodate the required nuclear payload, forcing a modification of the fuselage to be considered should the DH.111 design be advanced.
In the end, Air Ministry officials elected not to pursue this somewhat promising, yet ultimately questionable, de Havilland bomber entry - this while the Royal Air Force was already awaiting the results of a handful of other more potential and possible higher-performing bombers in the pipeline. Brief thought was also given to keeping the DH.111 on hand as an "insurance policy" against these complicated aircraft in much the same way the Short "Sperrin" was retained (this aircraft is detailed elsewhere on this site) but this came to naught. As such, the DH.111 fell to history after it was ended on October 22nd, 1948.