Avro 730
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The Avro 730 was a planned British Mach 3 reconnaissance aircraft and bomber for the Royal Air Force. It was cancelled in 1957 along with other development on manned aircraft as part of the 1957 Defence White Paper.
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[edit] History
During the early Cold War, the RAF bomber fleet of V-bombers was given the nuclear deterrent role. For strategic reconnaissance both pre- and post-bombing, an operational requirement, OR.330, for an aircraft was identified and a specification was drawn up in 1954 for an aircraft that could enter the Soviet Union while avoiding their air defenses. The aircraft envisaged would have be capable of maintaining Mach 2.5 at 60,000 feet, with the ability to reach Mach 3, and operate at a maximum range of 5,000 nautical miles.
There were submissions from the major UK aircraft manufacturers: the Handley Page HP.100, Vickers SP4, English Electric P.10, Avro Type 730 and a Short Brothers entry. All were futuristic delta or needle shapes in appearance employing several engines 12 on the HP.100, 16 mounted horizontally at the rear of the Vickers. The English Electric used ramjets.
Avro were given a contract in 1955 to develop their submission aircraft as the Type 730. As an aid to development the Bristol Type 188 research aircraft was built to test the wing shape and later effects of prolonged supersonic flight on metal. The first prototype was planned to fly in 1959. The first prototype was being built when the minister, Duncan Sandys, announced the decision to cancel. The Bristol 188 project continued though.
[edit] Design
The initial Avro 730 was based around a long and thin fuselage with a high fineness ratio, a requirement for sustained high-speed flight. A small almost-rectangular wing was mounted just rear of the midpoint of the fuselage, swept slightly to the rear along the leading edge and to the front along the trailing edge. Four Armstrong-Siddeley P.156 engines were carried, two each mounted over-under in pods at the extreme tips of the wings. No conventional canopy was fitted in order to maintain the fineness ratio, instead the cockpit featured only two small windows facing to the side, and used a retractable periscope for landing. A crew of three would be carried, pilot, navigator and radar operator.
This initial version was intended strictly for the reconnaissance role, using its "Red Drover" sideways-looking radar to find targets for attack by the V-bomber force that would follow. As development progressed it became clear that the radar would need a much smaller antenna than initially believed, freeing up considerable internal room. In response, the RAF started concentrating on the secondary bombing role carrying both the radar and also including a long bomb bay for either a weapon or additional fuel. A high-speed bomber requirement was also being studied at the time, OR.336, so the two projects were combined into the new RB.156 requirement. This led to a fairly major redesign.
Although the new version looked much like the original, it was larger overall and featured a new wing planform. Unlike the original rectangular design, the new version used a delta wing that grew progressively more swept toward the tips, at about 45 degrees inside the engine pods, and about 60 degrees outside them, the pods having been moved inboard slightly to about the 2/3rds span point. The engine pods were now specified to carry four Armstrong-Siddeley P.176 engines each, for a total of eight. The pods were circular at the front and mounted a single large shock cone, and grew progressively more "square" to the rear, where they ended flush with the rear of the wing. The rest of the layout was generally the same as the earlier version, with the rectangular canards, "hidden" cockpit and large cropped-delta vertical fin at the extreme rear.
The new version also allowed for a reduction in crew to two, although the reasons for this are not clear considering it still carried the same equipment, and potentially more. The bomb bay was narrow but very long at 50 ft, and was intended to be armed with a nuclear-tipped standoff missile. A suitable warhead started development as Blue Rosette.
Specification for reconnaissance version
- Length: 163 feet 6 in
- Wing span: 59 feet 9 in
- Wing area: 2,000 square feet.
- powerplant: 4 Armstrong Siddeley turbojets .
- weight: up to 200,000 lbs
[edit] See also
- Operational Requirement F.155 - the planned opposition to the expected Soviet high flying supersonic attackers
