By late 1955, Avro realized that, thanks to the alterations that had needed to be carried out to the 730, the fuselage was fatter, the wing trailing edge had been straightened and there was further wing area added, outboard of the engine nacelles. It was decided that more power was needed, so a revision led to the adoption of eight Armstrong-Siddeley P.176 engines which would be fitted in a square box four arrangement, with a single movable centre body controlling the airflow to all four engines in each pod. The wing area grew to 2,100 sq ft (196.09 m2), with the span increased to 65.61 ft (20.00 m). However length was reduced to 159 ft (48.46 m). The fuselage diameter rose to 9.35 ft (2.85 m) instead of the original 7½ ft (2.28 m). A test house was built at Avro’s, that could accommodate a full-size airframe, and would allow the simulation of skin temperatures at Mach 2.5. The Chadderton factory had set to work on the first fuselage when the infamous 1957 White Paper from Duncan Sandys appeared on the scene. OR.330 was abandoned, with all efforts now put towards the Blue Streak ballistic missile programme, which also was subsequently cancelled. Although development of the Avro 730 was estimated to reach a cost of £100 million over ten years, it would have been able to meet its aims as far as structurally and aerodynamically. However, with regards to the systems planned for it, these may have caused delays to service entry, in a similar fashion to those proposed on the later TSR.2. However, if one example at least could have been retained for high-speed research for the SST programme, then the money would have been well spent. As it was, when the fuselage of the Avro 730 was broken up, the stainless steel honeycomb sections, ended their lives as giant circular bins for depositing metal refuse in the factory. Some of these bins, even found themselves moved to Woodford and were last used on the abortive Nimrod MRA.4 programme! However, the wing shape of the Avro 730 was to finally be seen in the skies over Britain. As mentioned in my earlier post, Bristol had been allocated to the production of one of the Avro 731 airframes. In fact they were further along the path than Armstrong-Siddeley. It was decided that the aircraft would be modified to allow for the testing of a stainless steel structure at high-speeds. Unlike Avro’s manufacture technique, Bristol opted to use a puddle weld process, which actually added to the delays in getting the Bristol 188, as the revised design had been called, into the air. Other modifications to the airframe included moving of the cockpit to a further forward position, the adoption of a conventional tailplane, instead of the canard surface, moving the wing forward, dude to the lack of canard surfaces and the inboard wing sections made straight, instead of the swept design of the Avro 730. When the 188 did finally take to the air, it was found the DH Gyron Junior engines, selected for their high thrust, were so fuel-thirsty that the flights were not able to be of any significant duration, to allow for decent test results to be made. The failure of the Bristol 188 cost the UK taxpayers £20 million, with the Gyron Junior engine scrapped, and there not being any other application for an airframe like the Avro 730/Bristol 188. Here’s a GA of the final configuration of the 730 with its eight engines.
Posted on: Wed, 23 Jul 2014 19:10:34 +0000
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