General Dynamics F - 111K The General Dynamics F - 111K was a planned variant of the General Dynamics F - 111 Aardvark medium - range interdictor and tactical strike aircraft , developed by General Dynamics to meet a requirement for such an aircraft for the Royal Air Force . The aircraft was planned as a hybrid of several variants of the F - 111 as a way of producing an aircraft for the specific needs of the United Kingdom . The project was initiated in 1965 following the cancellation of the BAC TSR - 2 strike aircraft , with 50 units ordered in 1967 , only for the order to be subsequently cancelled a year later . Development . Background . In the early 1960s , the British Aircraft Corporation was in the process of developing a new strike aircraft for the Royal Air Force to replace the English Electric Canberra . This aircraft , designated as " TSR - 2 " ( Tactical Strike and Reconnaissance ) . The large set of requirements listed by the government for the new strike aircraft to undertake had led to TSR - 2 becoming a hugely complex machine , as it was intended that it be able to undertake both conventional and nuclear strike missions at high and low level , in all weathers , at supersonic speeds . As a consequence , the costs of the project began to increase , leading to it becoming the most expensive aviation project in British history , at a time when defence spending was being cut . This led to the RAF being asked to look for potential alternatives to TSR - 2 , in the event of it being cancelled . At the same time , the Royal Australian Air Force were also looking for a Canberra replacement , and were looking at a number of options , including both TSR - 2 and the General Dynamics F - 111 then being developed for the USAF ' s TFX programme . The uncertainty over TSR - 2 led to the Australians selecting an adapted version of the F - 111 in 1963 . The RAF were asked to evaluate the F - 111 as a cheaper option for the strike aircraft requirement , although the incoming Labour government denied it planned to cancel the British aircraft . This denial was reversed in April 1965 , when TSR - 2 was cancelled and a decision taken to look into the option of acquiring up to 110 F - 111s instead . No firm commitment was made to the F - 111 until the publication of the 1966 Defence White Paper , although it was the government ' s preferred option . Following the publication of the defence review , it was announced that up to 50 F - 111s would be procured for the RAF ; like the Australian version , these would be highly adapted to suit the unique set of British requirements . The intention was to form an initial four operational squadrons , plus an OCU , with two stationed in the UK and two forming part of the UK ' s forces East of Suez . The intention was that long - range , land based F - 111s would be used to replace the strike capability of the CVA - 01 aircraft carriers that were cancelled in the White Paper . Although there was no public announcement as to specific squadrons that would receive the F - 111 , a document from early 1966 by the AOC - in - C of Bomber Command , Air Chief Marshal Sir Wallace Kyle , indicated that 12 Squadron ( then a Vulcan squadron assigned to the strategic nuclear role ) , together with the inactive 7 , 15 and 40 Squadrons , would receive the aircraft upon their delivery . In April 1966 , a firm order was placed for 10 F - 111s for the RAF , with options for another 40 , covering the standard F - 111K models and a number of dual - control TF - 111K trainers , with the purchase price set around £2 . 1m ( $ 5 . 95m ) per unit ( 1965 prices ) . This was intended to show a significant reduction in cost when compared with the development and estimated production costs of TSR - 2 . At the same time , a pair of Victor squadrons had been moved out of RAF Honington , which was earmarked for conversion to accommodate the F - 111 force . However , at the same time the actual cost of F - 111 production had increased ; in April 1967 , when the RAF ' s 40 additional aircraft were ordered , the per unit cost of the F - 111C for the Royal Australian Air Force was US $ 9m . This eventually led to an admission from the British government that the cost would increase from the initial figure set out - in 1967 , the then Secretary of State for Defence , Denis Healey , stated that adjusting for inflation was taken into account , which would add approximately 2 . 5 % to the cost of each aircraft . This did not include the cost of installing the British adaptations . The total estimate cost by the time the last aircraft was due to be delivered in 1970 was approximately £2 . 7m . Despite this , the government still maintained that the F - 111 programme ( combined with the proposed AFVG ) would be cheaper than TSR - 2 to the tune of approximately £700m . Cancellation . The first two aircraft began assembly in July 1967 , and were issued with the serial numbers XV884 and XV885 . These were intended as development aircraft , to undertake airframe , avionics and weapons testing prior to them being refurbished as operational units . At the same time , the remainder of the planned 50 strong fleet were allocated serials from XV886 - 887 ( TF - 111K ) and XV902 - 947 ( F - 111K ) . The first two airframes were in the final stages of assembly at General Dynamics ' plant at Fort Worth , Texas in early 1968 when the Government then issued a new policy that would see the majority of British forces stationed East of Suez withdrawn by 1971 . At the same time it also decided to cancel the F - 111K procurement . The devaluation of sterling in 1967 had led to the per unit cost rising to approximately £3m . Additionally , the production schedules were slipping ; while the RAAF had its first F - 111 delivered in 1968 , official acceptance of the type into service did not occur until 1973 due to structural and development problems ( which led to the RAAF having to lease 24 F - 4 Phantoms as an interim measure ) . All of the components that had been assembled for the production of the main F - 111K fleet that shared commonality were diverted to the FB - 111A program , while the two aircraft under construction were re - designated as YF - 111As with the intention that they be used as test aircraft in the F - 111A program . Ultimately however , the two F - 111Ks were never operated as test aircraft - in July 1968 , almost exactly a year after the first airframe began construction , the US Air Force decided not to take them over , and General Dynamics were ordered to use them for component recovery . Replacement of F - 111K . The cancellation of the F - 111K still left a requirement for a strike aircraft to replace the Canberra , so the government ordered 26 new Blackburn Buccaneer aircraft for the RAF to operate alongside ex - Fleet Air Arm Buccaneers that were being moved to the air force following the phased withdrawal of fixed wing carrier aviation in the Royal Navy - somewhat ironically , the Buccaneer had been rejected as a contender for the original RAF requirement that had led first to the selection and cancellation of TSR - 2 , and subsequently the F - 111K . The first Buccaneer squadron ( 12 ) became operational at RAF Honington in 1969 . With responsibility for the UK ' s nuclear deterrent passing to the Royal Navy in 1969 , Avro Vulcan s were transferred from the strategic bomber role to the long range air interdiction role that would have been fulfilled by the F - 111 . The ending of the F - 111 procurement , combined with the cancellation of the Anglo - French Variable Geometry project , led to Britain eventually joining the multi - national working group to develop the " Multi - Role Combat Aircraft " in 1968 ; this led to the formation of Panavia and the ultimate development of the Tornado , an aircraft that assumed the roles of low - level strike and long range interdiction planned for the F - 111 . Design . The British version of the F - 111 was designated as the F - 111K . This was to be based around the airframe of the original F - 111A version built for the U . S . Air Force , but was to feature a number of alterations and adaptations . Structurally , the aircraft would be similar to the Australian F - 111C , with longer wings taken from the carrier based interceptor version and the heavy duty undercarriage from the strategic bomber version . This allowed for a greater gross weight to be designed into the aircraft . The other major design change from the F - 111A was in its avionics , with the design calling for the Mark II package developed for the F - 111D version , which featured a new inertial navigation and attack system , incorporating the AN / APQ - 130 attack radar , an IBM on - board computer , a Marconi doppler radar and the AN / APQ - 128 terrain following radar . The plan was then to pair this avionics package with British designed and developed mission systems , of which the main elements were the reconnaissance capability and weapon carriage . The F - 111K was to feature a revised weapons bay , containing a new removable centreline weapons pylon , which was beneficial given the design of the underwing pylons - the F - 111 had four stations under each wing , but only the inner pair were designed to pivot , meaning that the outer pair could not be used with the wings in full sweepback mode . All of the weapon pylons featured British designed ejector rack units . The aircraft was given provision for a pallet inside the weapons bay that would feature a British designed reconnaissance system , with three camera windows located next to the nosewheel undercarriage ( which the US versions were not fitted with ) . The aircraft was designed with an aerial refuelling probe compatible with the " probe and drogue " system used by the RAF , similar to the one fitted to the F - 111B , although mounted differently .