by Damien Burke
P.17E
This was an abortive attempt to design a version of the P.17C fully capable of meeting all of the load and range requirements in GOR.339 while needing no conventional runway at all, operating in a completely VTOL manner. It fell foul of the vicious circle of ever-increasing structure and fuel weight needed. For a combat radius of 400nm (460 miles; 740km) the AUW would be 83,500lb (37,900kg); for 500nm (575 miles; 925km) it jumped to an impractical 182,000lb (82,600kg), and beyond that the figures soon converged on infinity.
P.17F / P.24A
After the initial brochure submission, English Electric and Shorts continued to play with the lifting-platform idea, and the P.17F was the first result, this being a fan version to be used as a military freighter with a higher payload of 35,000–45,000lb (15,875–20,400kg). This could be developed further by the removal of the launching and retrieving roles and associated equipment to create a larger civil VTOL platform, the P.24A. These are beyond the scope of this volume.
P.22
English Electric had also originally proposed a fighter variant of the P.17A, the P.22, on the basis that the P.17A’s high thrust-toweight ratio, large fuel capacity, moderate wing loading and aerodynamic docility made it readily convertible to the long-range interceptor role. The nose had space for a developed AI radar, and the weapons bay was large enough to carry five canisters of unguided 2in rockets (370 rockets in all) or a pair of air-to-air missiles (Blue Jay, later known as Firestreak, or the American nuclear-tipped Genie, then under investigation for possible use on the P.1B). All of these weapons would be housed internally, and the rotating bay door would allow the use of a trapeze to lower the missile or rocket canister out of the bay before firing. The aircraft would not have been a great dogfighter, but it could have made a valuable contribution to long-range defence against Soviet bomber formations. The continuing fallout from Sandys’ White Paper, however, made sure that English Electric killed off the P.22 itself before it got the company into trouble.
Variable sweep
Volume 3 of the English Electric/Shorts submission included a chapter on the more novel designs that had been studied. The first was a variable-sweep wing. After trials of various planforms a wing that, when fully swept, was similar to that of the P.1, was felt to the most practical. It pivoted on a translating pivot point in the fuselage, thus dealing with the shift in aerodynamic centre as the sweep angle changed. High loads on the centre section in the unswept position would require a complex and weighty mechanism, with a variety of difficult problems to solve for which English Electric could find no existing helpful research material. Carrying stores under the wing and fuel within it was felt to be impractical, and the provision of electrical and hydraulic services to the wings would be difficult. The wing would have to be thicker, too, to provide sufficient lift in the landing configuration, though it could be smaller in area than the existing P.17 delta planform, with resultant higher wing loading; fine for low level, but an embarrassment for high-altitude performance. Overall, English Electric could see only small possible advantages and a slew of disadvantages.
Flexibly mounted wing
As a method of gust alleviation to improve crew comfort, a proposal was made to mount the wing on large dampers within the fuselage, with a pivot point from the front spar to a reinforced frame in the fuselage. This introduced large structural, weight and drag disadvantages, as the wing could no longer carry any fuselage loads and would be mounted higher than normal, and a large variable cowling would be required to fair it in to the fuselage at the rear. The slight advantages of lower airframe and crew fatigue were insufficient to justify proceeding with this idea.
Variable-incidence wing
Raising the wing leading edge by jacks and pivoting by the rear spar was seen as a way to improve the take-off lift coefficient and improve STOL performance. However, with an additional angle of incidence of 10 degrees being needed for a worthwhile improvement, this would have resulted in the front of the wing being raised 4ft (1.2m) above the fuselage. A similar scheme had been used on the Vought F-8 Crusader, but on a much smaller scale, and it was felt that it would be impractical on the P.17. Consquently English Electric, unlike de Havilland, soon abandoned this idea.
P.17Z clipped wing and narrow delta
Assuming the P.17D lifting platform was developed, and the strike aircraft could be acceptable if made entirely reliant on the platform, two P.17 variants were proposed, one a fairly careful and obvious progression and the other a much more extreme example of what could be possible. With the platform taking the aircraft up to 250kt (290mph; 460km/h) before parting company, a smaller wing and lower-thrust engines would be possible. The first suggestion was a variant of the P.17A with a smaller wing (reduced from 610sq ft to 415sq ft (38.5sq m) and span down to 28.8ft (8.78sq m)), the undercarriage deleted and the space used for fuel (thus offsetting the loss of wing fuel space), along with RB.133 engines (whose lower thrust would no longer matter as there was no take-off case to deal with). The second, much more radical suggestion bore no relation to the other P.17 designs whatsoever, and was instead based on a narrow delta shape that had originated from RAE theoretical work, optimized entirely for supersonic cruise at low level. This was very much ‘finger in the air’ thinking, with very little work on the shape having been carried out and much research still needed.
A P.17 design with variable-sweep wing. Unlike later successful VG designs, this wing used a single central translating pivot point to cope with the shift in aerodynamic centre at different sweep angles. English Electric considered wing fuel and underwing stores impractical on a variable-sweep wing. BAE Systems via Warton Heritage Group
A general-arrangement drawing of the English Electric P.17Z. Damien Burke
Other novel layouts
Some idea of the broad scope of English Electric’s brochure will now have been gained; yet there was more! A variety of much less conventional overall airframe layouts was combined with various engine configurations to see if the benefits of the P.17B and P.17C could possibly be combined with the performance of the P.17A. These included a canard layout with two podded Olympus engines embedded in the wings and two Orpheus lift engines in the fuselage; another canard with two Olympus 21Rs in the fuselage fed from a ‘sharkmouth’ ventral intake and two Orpheus lift engines mounted in knife-edge pods under a delta wing; a similar canard delta but with a dorsal intake feeding tilting Olympus 14 engines in the fuselage, and large underwing pods for Orpheus engines with simple aft/downward thrust vectoring; and a twin-boom layout with a modified delta wing, Olympus 21Rs in the booms and Orpheus lifting engines in the central fuselage pod. The least bizarre layout was a fairly minimal variation on the P.17A with twin fins and extra intakes on the fuselage sides behind the wing leading to the Orpheus 12R engines; the forward-mounted intakes led to Orpheus lift engines which had a thrust-vectoring plate to allow them to thrust either to the rear or vertically downwards. Each variation showed some advantages for particular types of operation, if only minimal ones, but the effort and risk involved in developing each of these configurations was felt to be excessive.
English Electric also looked briefly at other possibilities of off-airfield operation, including tail-sitting VTOL and ‘zero-length launchers’ (i.e. being mounted on a road vehicle and fired into the air by powerful rockets), but concluded that both ideas were impossibly handicapped by the sheer size of the aircraft. Road transport, even with various bits folded or dismantled, would introduce strict route limitations because of the size of the trailer, and that was even before the problems of developing a launcher came into it. A recent mishap involving one of the US Army’s huge atomic cannon, which had ended up firmly embedded in a 12ft (3.6m)-deep ditch while being transported from one site to another in West Germany, also illustrated the hazards that could be expected in transporting large and heavy loads over even well-mapped territory (the damage to a TSR2 airframe on delivery to Boscombe Down seven years later would provide an ironic additional
demonstration of the risks).
Finally, the possibility of ducted-fan lift was examined. Fans had better lifting efficiency but introduced great structural difficulties. The major problem was the need to pass a large volume of air through an area of the aircraft that had to be fairly structurally dense to cope with the loads experienced, particularly during low-level operations. This would naturally result in a larger aircraft, which would be heavier, and thus ran the risk of cancelling out the lifting gains. The optimum layout that English Electric could come up with was a canard design with RB.142Rs mounted in the fuselage, driving a battery of eight ducted fans exhausting downwards. In normal flight, no penalty (other than the added weight) would be incurred; for STOL operations intake louvres would be opened on the upper fuselage and part of the engine thrust directed to drive the fans. Further louvres underneath would open to allow the relatively low-speed fan exhaust out, with the louvres acting as thrust deflectors to enable transition from high to low speeds and vice versa. In this configuration, the two engines, producing 28,000lb (13,000kg) of thrust, would be augmented by the eight fans and produce a 70,000lb (32,000kg) vertical thrust component for a weight penalty of around 5,000lb (2,300kg). However, the large volume required by the fan bay would result in an aircraft significantly larger than the P.17A, and, with no quantitative data available on fan efficiency, English Electric left this as an academic exercise.
English Electric followed up its weighty tome on the P.17 and its variants with a summary document that attempted to focus Ministry minds on the urgency of the requirement and the need for minimum delay in making a decision. The company hammered home the point that the P.17 airframe had already entered the detail design stage, was firmly based on their experience with the Canberra and P.1 (much more the latter, of course), and that it was the only aircraft that could meet the 1964 in-service deadline.
Fairey – Project 75 Tactical Strike/Reconnaissance Aircraft
Fairey’s submission to GOR.339 was a basically delta-wing aircraft with engines in pods hung under the wings. Unusually, though, it chose a canard layout and side-by-side seating for the crew, very much in the style of the Second World War de Havilland Mosquito. In its brochure Fairey first addressed the whole question of VTOL, and concluded that it would simply result in an excessively heavy aircraft carting around a load of structure and engine weight that would be of no use during the sortie, along with the fuel reserve needed for a VTOL landing. Fairey was striving for the reverse of this; the smallest, lightest aircraft possible for the task. Ideally this would be a tailless delta, but the problems of meeting the take-off and landing-roll requirements meant that a conventional tail would be required. To make room for the required fuel and bomb load, the fuselage would be unable to hold the engines, so these would be mounted in underwing pods. This then brought up the problem that a low-set tailplane, the only viable location for transonic operation, would be bathed in jet wash. The solution was to choose a canard configuration, though it was acknowledged that this risked some unwanted interaction between the fore-plane and the engine intakes.
Leading Particulars: Fairey Project 75
Length
100.75ft (30.71m)
Height
17.75ft (5.41m)
Wing span
34.66ft (10.56m)
Wing area
600sq ft (55.74sq m)
Wing aspect ratio
2
Foreplane area
228sq ft (21.18sq m)
Fin area
183sq ft (17.00sq m)
Engines
2 × RB.142R
Max speed
750kt (860mph; 1,390km/h), Mach 2.2
@ 36,000ft (11,000m)
Empty weight
32,910lb (14,940kg)
Max AUW
65,900lb (29,910kg)
The navigation system was to vary with the phase of the flight; inertial navigation and Doppler for the high-level part of the sortie, inertial only for the descent to low level, and then switching to X-band ‘side viewing radar’ at low level. The FLR would be a development of Ferranti’s AI.23 set, and would handle terrain clearance and target identification. The resulting large nose radome required a wide fuselage, which as a bonus gave enough room for side-byside crew seating. The pilot would sit further forward, however, so that his view would not be obscured to one side and the navigator would have more room for his equipment. An offset seating position benefited the pilot, as the high angle of incidence on approach to landing would result in the nose obscuring his view of the runway if he was seated centrally. By being offset to the side by several feet a much-improved view was possible. The navigator’s main instrument panel was ahead of him, with a further panel to his left, blocking his direct view in that direction. The view downwards and sideways to aid photographic reconnaissance was through a smaller window inset in the starboard cockpit side. The navigator’s seat could be motored down a foot to give him a better angle of view through this window. Contrail detection was by the Mk 1 eyeball, a rear-view mirror enabling the pilot to see the wingtips, the most likely source of contrails.
Below the cockpit were the SLR aerials, and aft of the cockpits and forward of the bomb bay was a large equipment bay. The bomb bay would have a rotating bomb beam, as Fairey believed traditional doors would introduce unacceptable buffet in transonic flight. A side door would open briefly during the rotation period (a clever arrangement of jacks linking both the door and beam to eliminate the use of complex sequencing valves and microswitches), allowing the larger stores to clear the side of the bay, and close again once the beam was fully rotated and the stores were hanging in the air stream. The bay had room enough for all of the stores mentioned in the GOR, including six 1,000lb HE bombs. With the bay located just ahead of the c.g., stores release would cause a c.g. shift that would need to be trimmed out by canard movement. To mount a reconnaissance pack in the bay, the bomb beam and both opening and fixed side doors would be removed first. The reconnaissance pack would consist of various cameras, sideways-looking reconnaissance radar with a moving target indicator, and linescan recording and transmission equipment. A buddy flight-refuelling pack was also an option.
A general-arrangement drawing of the Fairey Project 75 of January 1958. Damien Burke
An artist’s impression of Project 75. BAE Systems via RAF Museum
The Project 75 pilot’s cockpit; the offset seating improved the pilot’s view during the approach to land. BAE Systems via RAF Museum
The Project 75 navigator’s cockpit. The navigator had various blinds he could pull across his outside view to allow a clearer view of his various radar scopes and instruments, and a small window on the right provided some downward view. BAE Systems via RAF Museum
A subsidiary equipment bay was located aft of the bomb bay, with access through the main undercarriage bay roof (similarly, the front equipment bay was reached via the nose undercarriage bay). Dive brakes were mounted on the rear-fuselage sides, extending outwards up to 90 degrees. A braking parachute container was mounted in the extreme tip of the rear fuselage, too, housing three 10ft (3m)-diameter parachutes that would be deployed in a cluster. Flexible bag-type fuel tanks were also distributed about the centre portion of the fuselage, with integral tanks within the wing. For self-protection, RWRs could be mounted in the rear fuselage around the base of the fin. Radar-absorbing material would be used within the cockpit, behind the nose radome and in the intakes; possibly in the jet exhausts as well.
The undercarriage comprised tandem twin-wheel nose and main-gear bogies retracting rearwards into the fuselage, with outrigger wheels extending from the engine pods and also retracting to the rear. The aircraft’s ‘sit’ on the ground was very nose-high to aid unstick on take-off, resulting in a huge and ungainly looking nose gear leg. Nosewheel steering was aided by differential braking on the outrigger wheels. The outrigger units were not handed, cutting down on the amount of spares backing needed.
For the wing, Fairey stuck wit
h the 60-degree swept delta of the Fairey Delta 2, and chose not to go with any form of leading- or trailing-edge flap blowing, citing expense and maintenance difficulties. The wings had conventional flaps and ailerons, and the canard foreplanes were all-moving. The inner wing housed integral fuel tanks, with outer integral tanks holding water-methanol used to restore engine thrust in hot-and-high conditions. The fuel system itself was fully automatic and self-balancing. In-flight refuelling was catered for via a retractable probe mounted ahead of the pilot on the port side of the nose. The chosen engines were RB.142Rs, in common with many other submissions, though provision was also made to take the Olympus 15R. Access to engine controls was via a removable engine pylon leading edge, and the front and rear fairings of the engine nacelle could be removed to enable with drawal of the engine or its associated reheat unit.
A Project 75 production breakdown. BAE Systems via RAF Museum
With the aircraft spending most of its flying life below Mach 1, conventional light-alloy construction sufficed, using the structural techniques Fairey had developed for the FD2 of clad sheet, forgings and extrusions. Fairey struck a confident note in its brochure when it came to being able to design and build the aircraft successfully. The company’s experience on the FD2 would cut down on the aerodynamic and structural work necessary, and its experience with Gannet production, including envelope jigging, would ensure a smooth production run with good component interchangeability characteristics, enabling assembly of components at dispersed sites. Fairey predicted first flight two years and three months after receipt of the contract, and peak production of sixteen aircraft per month, rising to thirty per month when using the production facilities of an associated company. (No particular company was specified in the brochure, though Blackburn was selected as the preferred associate in the covering letter.)
