by Damien Burke
The undercarriage was of orthodox tricycle layout, both the nose and main units retracting rearwards into the fuselage. Avro did not put any serious effort into dealing with the whole question of airfield performance on rough strips and short runways, and as a result the 739 fell short of the requirement when it came to take-off distances, needing rocket assistance to meet the sortie requirements if supersonic bursts were included, and even then being unable to manage the 1,000nm sortie’s take-offdistance requirement. Avro felt that keeping the aircraft as small as possible was extremely important, and thus planned to build it large enough to be able to manage only the 600nm sortie on internal fuel. The 1,000nm sortie would require drop tanks, jettisoned before going supersonic, and AUW in this configuration (one Red Beard internally, two 600gal (2,730L) drop tanks) would be around 91,000lb (41,300kg) if the lightest of six suggested engines was chosen. A considerable excess was available when it came to ferry range, where the aircraft could manage up to 2,830nm (3,250 miles; 5,240km) with drop tanks. While the GOR specifically mentioned that subsonic cruise was to be no lower than Mach 0.95, Avro chose Mach 0.9 as being near enough. Avro’s preferred engine was the Rolls-Royce RB.142R, which would appear in most submissions to GOR.339. It also listed two flavours of Conway and three flavours of Olympus, the Conway needing least development but giving the highest AUW at 97,130lb (44,090kg) for the 1,000nm sortie with supersonic burst.
The construction was to use tried and tested techniques, light alloys being used wherever possible and exotica like titanium being employed only for the flap blowing tubes, reheat pipe heat shields and other areas requiring great heat resistance and strength. In terms of production responsibilities and teaming up with other firms, Avro’s submission was weakened by its wish not only to have overall control of the airframe but also to handle the flight control system itself, and take charge of the radar-navigation-bombing system and any contractors brought on board for this equipment, with vague mentions of using the appropriate design, technical and experimental resources of the rest of the Hawker Siddeley Group. The company predicted that, if a specification was in hand by January 1959, it could have the first of fifteen development-batch aircraft in the air by November 1961, with full CA release by September 1964.
Barnes Wallis–Vickers Type 010 Swallow Momentum Bomber
Barnes Wallis, the inventor of the ‘bouncing bomb’ of Dambusters fame, had been working on variable-sweep designs since 1948, with partial funding from Vickers as a pure research programme and some desultory contributions from government. He had come up with the ‘Swallow’, a remarkable tailless design with a variable-sweep wing (from 15 to 75 degrees), an 80-degree swept forebody and eight engines, mounted in paired nacelles mounted above and below the wing, near the tips. These swivelled to retain their fore-and-aft orientation when the wing sweep changed, and tilted up and down to provide flying controls. No conventional control surfaces were to be provided. Wallis claimed that a suitably sized bomber version could cruise at high altitude at Mach 2.5 and deliver a 10,000lb (4,500kg) bomb load to a target up to 2,500 miles (4,000km) away and return, with no hope of fighters being able to reach its altitude, or catch it if they could. Unfortunately he had been unable to convince the government to fund a research vehicle, and his Swallow project had never got off the ground. While the Air Staff had shown keen interest in the concept, asking Wallis in late 1956 to submit a brochure for a Swallow variant to satisfy OR.330 (a high-altitude supersonic bomber requirement), Duncan Sandys unilaterally cancelled Wallis’s research programme in early 1957, even before publishing his Defence White Paper, in spite of objections from the Air Staff. Wallis, undeterred, went ahead and submitted his brochure on Swallow to OR.330 in February 1957, but OR.330 too was killed by Sandys, and consequently the Swallow was never assessed in that role. The Air Staff continued to show interest in the Swallow throughout 1957, provoking a slap-down from the MoD in August of that year, in which it was stated that the Swallow was not to be proceeded with.
Leading particulars: Swallow to GOR.339
Length
77ft (23.47m)
Height
9ft (2.74m)
Wing span
37ft (11.27m) swept,
90ft (27.43m) unswept
Wing area
727sq ft (67.54sq m)
Wing aspect ratio
1.88 swept, 11.14 unswept
Engines
4 × Bristol Olympus 12
Max speed
Mach 2.0 @ 50,000ft
(15,000m)
Empty weight
22,805lb (10,350kg)
Max AUW
43,935lb (19,940kg)
With GOR.339 on the table just weeks later, Wallis made another attempt to convince the government of the viability of his schemes, putting forward a preliminary brochure on a variable-sweep aircraft to meet GOR.339. This was a Swallow variant, the Type 010. Two versions had been schemed, a large one using existing turbojet engines (the Bristol Orpheus BO412), and a smaller aircraft using idealized engines based on project studies from Bristol (the BE36) and Rolls-Royce (the RB.121), better matched to the Swallow design. Both differed from Wallis’s original Swallow proposal in having a deeper forebody, a redesigned tandem cockpit (without the rising turret of the original design), and four engines rather than the eight of the original. As an alternative a single Gyron PS.52 engine could be mounted in the fuselage, but this would require conventional control surfaces and additional structural weight to cope with them, and the wings would have had to be stiffened to resist flutter now that the wing-mounted engines were absent.
The larger aircraft with Orpheus engines was to have an AUW of 43,935lb (19,9450kg) and a ferry range of 2,700nm (3,100 miles; 5,000km). The AUW of the smaller aircraft with idealized engines would be just 30,000lb (13,600kg) and it would have an incredible ferry range of no less than 5,000nm (5,750 miles; 9,250km). For the 1,000nm sortie Wallis sketched a hi-lo-hi flight plan in which the aircraft would cruise climb at Mach 0.9 to 36,000ft (11.000m) to begin with, increasing to Mach 2.0 before descending to 1,000ft for a just-subsonic attack run, and then returning to Mach 2 and high altitude for the return home. Instead of carrying a 1,650lb (750kg) atomic weapon, the aircraft could carry four 1,000lb HE bombs, seventy-four 2in rockets or thirty OR.1099 rockets. Day, night and radar reconnaissance would also be possible, though no details were provided.
Barnes Wallis shows off a magnificent model of his Swallow aircraft, a variation of which was proposed to satisfy GOR.339. BAE Systems
The Orpheus engines had significantly poorer fuel consumption compared with the RB.142 suggested for the Vickers Type 571, but as they had been selected for their ability to be used in a tilting fashion to control the aircraft, replacement with RB.142s would be difficult. Earlier RAE investigations into the Swallow had raised concerns about control loss if an engine failed, but Wallis had argued that this could be countered by a mechanical system to detect thrust loss and angle the remaining engines to compensate automatically, in less time than it would take for the pilot even to notice that something had gone wrong. In terms of satisfying GOR.339 the Swallow could not meet the take-off roll requirements, and all of Wallis’s figures excluded the additional weight of ‘assisted take-off units’ that would be required to enable it to do so. The RAE’s investigations into the characteristics of the design had also found that in the unswept condition the aircraft would also be so stable as to be difficult to manoeuvre, and the addition of a canard, or substantial redesign of the forebody, would be required. If this could be carried out and a realistic ‘idealized’ powerplant could be developed, however, the design had promise. Several meetings were held in September 1958 to assess the application of the Swallow concept to GOR.339, but it was felt likely that this would put back the entry into service by four years for dubious benefit. By October the RAF had concluded that there were just too many engineering problems to solve, and that the Swallow concept was better suited to a transport or high-altitude bombe
r than to GOR.339.
A general-arrangement drawing of the Vickers Type 010 of January 1958. The term ‘momentum bomber’ came about from the winged bomb mounted on the upper rear fuselage. This was designed to carry out its own delivery manoeuvre, using the momentum of the delivery aircraft. The Swallow would fly over the target, whereupon the bomb would be released and then pull into a half-loop and dive back down on to the target. Damien Burke
The chances are that, even if the aircraft had been theoretically perfect, politics would have killed it off regardless. Wallis was viewed with distrust by many in power, and a typical government bureaucrat assessment noted that Wallis ‘… works in an atmosphere of extreme secrecy and as he has got older he has become more and more difficult with the people actually working with him … … [He] has shown himself very resentful of any suggestions from the young men working with him, and for this reason has great difficulty keeping together a good team.’ As to the Swallow itself: ‘It looks extremely impressive but we have not so far found anyone who can understand it …’.
Blackburn and General Aircraft B.108
Blackburn once again submitted a variation of the NA.39 for consideration, though it had not been in the list of firms specifically selected to be asked for submissions. This time it was designated the B.108, and had moved on somewhat from the B.103 the RAF had originally derided back in 1955. At that time the actual aircraft had not been built, and was only the subject of an order for a development batch. Now, two years down the line, the NA.39 had evolved somewhat in capability as well as appearance. The nose extension of the B.103A had been incorporated; a spine along the fuselage contained control runs and made more room for internal fuel; the selection of a single radar installation for the nose radome had been made, and the radome and its fold line redesigned to suit. This was basically similar to the aircraft that has since become familiar as the Buccaneer S.1.
The B.108 had other changes too. That fuselage extension was in the area of the cockpit, giving 18in (46cm) more room for radar displays, which would be needed, as the aircraft had SLR in the forward fuselage to provide fix corrections for the new INS. The underwing slipper tanks were enlarged to give 60 per cent more capacity and enable the B.108 to just about manage the 1,000nm sortie. However, with a low-level cruising speed of just Mach 0.89, no realistic supersonic capability, and no improvements in take-off and landing performance, Blackburn had immediately given the RAF just the excuse it needed to discount the B.108 submission.
Support for the NA.39 to meet GOR.339 was strong from all other directions, however. Even a former Chief of the Air Staff, Sir John Slessor, wrote to Duncan Sandys in January 1958 to commend the NA.39 to him, albeit as an interim measure. At the time it was thought to be around three years in advance of any other type (including American ones), and it was surely worthwhile to have a stop-gap available right now that would be ahead of the game for three or four years, and could soldier on for eight to ten, by which time a really modern replacement could have been acquired. Blackburn indicated that Fairey would be its partner of choice if either company were to be awarded the contract to build an aircraft to satisfy GOR.339.
A general-arrangement drawing of the Blackburn B.108 of January 1958. Damien Burke
Later, in February 1960, Blackburn suggested a further upgraded aircraft, the B.111, re-engined with the new Rolls-Royce RB.168 (Spey) of 19,250lb (8,740kg) thrust (in reheat), with all naval features deleted; an effort owing a lot to the Buccaneer S.2, albeit with reheat. The B.111 would be supersonic, with a top speed of Mach 1.25 at high altitude, normally cruising at Mach 0.85. If it stayed subsonic, combat radius would be 840nm (970 miles; 1,550km), and the AUW for this sortie would be 46,988lb (21,328kg), with a take-off roll of 1,800yd (1,650m) and landing roll of 1,070yd (980m). Only by carrying drop tanks could the B.111 manage the 1,000nm sortie. Predictably, with the TSR2 by then well under way, the RAF was still not interested.
After that, Blackburn gave up any serious efforts to try and get in on the TSR2 act, though it did come up with another improvement, the B.113, which differed primarily from the B.111 in having a reshaped fuselage and greater fuel capacity, giving it combat radius of 1,290nm (1,480miles; 2,390km) with external tanks and an AUW of 54,200lb (24,600kg), along with a claimed top speed of Mach 1.85 at altitude. This was aimed at a possible Royal Australian Air Force (RAAF) requirement for a strike and all-weather interceptor aircraft. The RAAF was not interested; and when the proposal was brought up in September 1960 by the MoA, the RAF was quick to point out that it was just a minimal improvement on an already unacceptable design.
Bristol Aircraft Type 204
Undoubtedly the most unusual design submitted to satisfy GOR.339 was Bristol’s Type 204. Bristol had put together a truly futuristic aircraft with a beautifully shaped ‘Gothic’ wing (so named because the curve in planform matches that of the ogival arches of Gothic architecture), above which sat a large box containing the engines and intakes, with a long nose extending from below the wing. Finishing off the aircraft’s striking appearance was a bizarre canard mounted on a ventral fin below the nose.
Leading particulars: Bristol Type 204
Length
79.5ft (24.23m)
Height
20.75ft 6.32m)
Wing span
32ft (9.75m)
Wing area
820sq ft (76.2sq m)
Wing aspect ratio
1.25
Foreplane span
8.5ft (2.6m)
Foreplane area
55sq ft (5.11sq m)
Foreplane aspect ratio
1.3
Fin area
127sq ft (11.8sq m)
Engines
2 × Bristol Olympus 22SR
Max speed
Mach 2.0 @ 52,000ft
(16.000m)
Empty weight
41,000lb (18,600kg)
Max AUW
81,350lb (36,925kg)
Bristol’s departure from the more conventional layouts favoured by other companies was its solution to the GOR’s demanding mix of subsonic and supersonic flight, low- and high-level performance, good gust response and fatigue strength, and excellent short-field performance. Bristol had already been working on designs for a supersonic transport, and the slender-delta wing (the classic ‘paper dart’ planform) was clearly the best for high Mach numbers. However, such a wing was far from ideal in the low and slow landing regime, and adding flaps to a delta wing that are big enough to be of any use also introduces such huge trim changes that the aircraft would be impossible to control. Modifying the delta by means of introducing an ogival curve to the leading edge, effectively rounding off the tips and apex, improved the wing’s stability (particularly at high angles of incidence) and was considerably less draggy than a standard delta. When the Gothic wing had first been drawn up, it was intended that an aircraft using it would be ‘integrated’, with the crew, equipment, fuel and engines all contained within the contour of the wing, which would be of very thick section. The requirements of GOR.339, particularly the sheer amount of fuel needed for the required combat radius, made an integrated design impossible, so Bristol added a long fuselage (almost doubling the aircraft’s length in the process), in which was housed the crew compartment, bomb load and electronic equipment. This also enabled Bristol to add a canard flying surface and thus deal with the trim changes caused by flaps, which could now be big enough to be unblown and still effective; they also doubled as ailerons.
A general-arrangement drawing of the Bristol Type 204 of January 1958. Damien Burke
The foreplane had a trailing-edge flap of its own, and was mounted underneath the nose on a ventral fin to give maximum span for the flap and keep the vortices from the foreplane away from the main fin. The foreplane itself was of identical planform to the mainplane, and in normal cruising flight would be all-moving for the limited trim power required in the cruise. The flap would be used only to trim out the large changes introduced by the use
of the wing flaps, and Bristol suggested that the foreplane flap might need blowing to be effective enough. Stability was expected to be acceptable through much of the envelope, but an autostabilizer would be necessary for comfortable handling.
