In today’s Sydney Flyer article, author Anthony Coleiro shares his most recent instalment of his X-Files series. This is Anthony’s 141st article under the ‘X-Files’ banner for the club magazine, and the first for 2022.
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FILE X141: BRISTOL T.188
Back in the day when the UK was interested in competing for speed supremacy in the air against the US, a specification was issued for a research vehicle that could reach speeds of Mach 2. Specification ER.134T was issued in February 1953, several firms responded and Bristol won the contract with their Type 188, the first turbojet conceived by their design team. While it was designed as a research vehicle to test kinetic heating effects on aircraft structures, the military became interested in the project as a single-seat high speed military interceptor. The faster you intend to go the more problems that you encounter and there were many to solve, after all that was the intent of the design, to find out what the problems were and find solutions.
The original engines Bristol intended to install were a pair of Rolls-Royce Avon RA.24R but instead a pair of 10,000 lb static thrust de Havilland Gyron Junior DGJ.10 afterburning turbojets that could operate to a temperature of 2000° Kelvin was substituted. The afterburners boosted thrust of these engines by another 40%. These engines were the first British engines designed for continuous running at supersonic speeds. These were pioneering engines introducing stainless steel and titanium into the building of jet engines and high temperature oils and fuel systems. Lessons learned with these engines were later applied to the Olympus engines that famously powered the Anglo-French Concord and the ill-fated BAC TSR.2 (the subject aircraft of my 39th article back in 2004).
At an altitude of 36,000 ft. and at Mach 2.5, the thrust produced by the Gyrons was predicted to rise to in excess 20,000 lb per engine.
Bristol received an initial order for six aircraft but this was later revised down to three with one of these airframes built for structural testing purposes.
With the anticipated stresses to the airframe, it was felt that aluminium construction would just not cut it; instead stainless steel was extensively used. This was not an easy material to make an aircraft out of and the construction suffered numerous delays while problems were being solved as they went. One of these problems that caused much delay was the fasteners. With kinetic heating comes expansion of metal, the trick was to find fasteners that had the same expansion rate as the metal it was fastening. One can imagine the effect on joints if the skin expands at a different rate to the rivets. A new form of welding was developed for this project but this proved unsatisfactory and assistance from Armstrong Whitworth was sought who had experience in such construction and as they were already building some important components under sub-contract for this project.
In 1957, the military lost interest in the aircraft and withdrew their financial support. Bristol on the other hand thought the research they were doing was far too important to let go so the project limped on as a private venture with the capital constraints that this imposes. It was not until April 1961 that Bristol finally got to the point where they had a completed aircraft. The aircraft was very sleek with a long 21.6 metre long fuselage and a relatively short 10.7 metre wingspan.
Testing had revealed more problems particularly with the engine intakes, the inner wing panels and the tail-plane position and it was not until a year later before the aircraft was ready to take to the air. The maiden flight was conducted by Bristol’s test pilot, Godfrey Auty taking off from Filton airport. The flight lasted 23 minutes terminating at Boscombe Down where he landed the aircraft at the Aircraft and Armament Experimental Establishment.
The second prototype was ready for flight in April 1963. The aircraft was tested over the English Channel and over the Irish Sea reaching a speed of Mach 1.88. Other engines were planned to be tested on the airframe to see if the speed could not be pushed out further to Mach 3.
After all that work, the careers of these aircraft was short lived, even though the fuselage contained extensive fuel tanks, it consumed fuel at such a high rate due to having very thirsty engines and leaking fuel tanks, a problem that was never resolved, that endurance at the required speed proved completely inadequate. Consequently, Mach 1.88 was the best speed the T.188 achieved so its type number proved to be rather prophetic in the end.
The first prototype went into storage at Filton in December 1963 and in March of the following year, the second prototype followed suit after it had racked up just 51 flights. They were struck off charge in November 1966 and transported to the Proof and Experimental Establishment at Shoeburyness to be used as gunnery targets. In 1974, the first prototype won a reprieve from certain destruction and was allotted for preservation at the Cosford Aerospace museum.
Even though the design intent was not achieved, enough data was collected and valuable lessons in construction were learned that this was put to good use in the development of the Concorde’s sleek fuselage.
Conde Nast Publications
The Illustrated Ency. of Aircraft
Empire of the Clouds
When Britain’s Aircraft Ruled the World
British Prototype Aircraft