| Bristol Type 188 | |
|---|---|
 Bristol Type 188 XF926 at theRoyal Air Force Museum Cosford | |
| General information | |
| Type | Experimental aircraft |
| Manufacturer | Bristol Aeroplane Company |
| Status | Experimental |
| Primary user | Royal Aircraft Establishment |
| Number built | 3 (one static test, two flight test prototypes) |
| History | |
| First flight | 14 April 1962 |
| Retired | 1964 |
TheBristol Type 188 is asupersonic research aircraft designed and produced by the British aircraft manufacturerBristol Aeroplane Company. It was nicknamed theFlaming Pencil in reference to its length and relatively slender cross-section as well as its intended purpose.[1]
The Type 188 was developed as part of supporting research efforts for theAvro 730, a later-cancelled bomber capable ofMach 3 flight. Its purpose was to explore high-speed, high-temperature flights; for the latter purpose, it made use of unconventional materials, such as large quantities ofstainless steel, as well as the incorporation of an activerefrigeration system. To work with this material, relatively exoticpuddle welding fabrication techniques were employed along with extensive technical support from external companies. As part of its intended test programme, the Type 188 was designed with flexible engine installations that allowed for the fitting of different air intakes, engines, and propelling nozzles. It was also furnished with extensive electronic sensors, data recording, andtelemetry apparatus. A total of three aircraft were constructed – a single static test frame along with two (constructor numbers13518 and13519) flight-capable aircraft; various scale models were also produced.
During May 1960, the first airframe was delivered to theRoyal Aircraft Establishment (RAE) at Farnborough. Themaiden flight of the Type 188 occurred on 14 April 1962. Flight testing encountered numerous problems, including the excessive fuel consumption of theDe Havilland Gyron Junior engines used, which did not permit the aircraft to fly at high speeds long enough to evaluate the "thermal soaking" of the airframe, one of the main research areas of the project. Across 51 flights, the Type 188 attained a maximum speed of Mach 1.88 (1,240 mph; 2,000 km/h) at 36,000 ft (11,000 m).[2]
During early 1964, it was announced that all activity involving the Type 188 was to be terminated. The project had cost £20 million by the end of the programme,[3] making it the most expensive research aircraft ever developed in Britain at that time.[4] The technical data and knowledge garnered from the Type 188 was put to use in other British high-speed aerospace efforts, most notably the development ofConcordesupersonic transport, as well as the Bristol (later Rolls-Royce)Olympus 593 powerplant, which powered both Concorde and theBAC TSR-2 bomber.[1] During the late 1960s, it had been intended for both of the Type 188 fuselages to be used as targets for gunnery trials at theProof and Experimental Establishment atShoeburyness, Essex; however,XF926 was subsequently transported toRAF Cosford, initially to act as instructional airframe 8368M, it has since been preserved at theRoyal Air Force Museum Cosford inShropshire.
The Bristol Type 188 had its genesis inOperational Requirement 330, which sought a high speed (Mach 3)reconnaissance aircraft, which eventually developed into theAvro 730.Air Ministry officials recognised that, as the Avro 730 was expected to operate at high speeds for extended periods of time, more data was needed on high speed operations; to fulfil this need, the follow-onOperational Requirement ER.134T was issued in February 1953; it called for a flyingtestbed capable of attaining speeds in excess of Mach 2. This aircraft was expected to run at these speeds for extended periods of time, allowing it to studykinetic heating effects on such an aircraft. Furthermore, it was also expected to operate for a considerable amount of time with askin temperature around 300 Celsius.[1][5]
Several of Britain's aircraft manufacturers took interest in this relatively advanced specification, Bristol Aircraft being specifically invited totendered by ministry officials.[5] The company's design team opted to produce a clean sheet aircraft design, which was assigned the internal designation ofType 188. The submitted design was somewhat vague and even speculative in several aspects, the aircraft's layout was not firmly decided upon until as late as 1955.[5] Nevertheless, following a competitive review of submissions, the associated contract6/Acft/10144 was awarded to Bristol during February 1953.
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The advanced nature of the aircraft meant that new construction methods had to be developed. Several materials were considered for construction and two specialist grades of steel were selected: atitanium-stabilized 18-8austenitic steel and a 12%-Cr steel used in gas turbines (Firth-VickersRex 448). These had to be manufactured to better tolerances in sufficient quantities for construction to start. The 12% chromiumstainless steel with ahoneycomb centre was used for the construction of the outer skin, to which no paint was applied. However, simply procuring sufficient amounts of stainless steel sheeting was a challenge, only compounded by factors such as the desired strength and uniformity.[5]
While traditionalriveting was considered to be a potential construction method, however, this posed substantially difficulties as every rivet,bolts, andscrews used would have had to be specially manufactured out of compatible materials to ensure the necessary tolerances were met.[6] Instead, a relatively cutting-edge technique ofarc welding using anargon gas shield, known aspuddle welding, was used. Another British aircraft manufacturer, theW. G. Armstrong Whitworth company, provided substantial technical help and support to Bristol during this period; they had also explored the use of puddle welding for advanced aerospace purposes. Armstrong Whitworth produced major sections of the airframe as asubcontractor.[7]North American Aviation used the same methods of argon welding of stainless steel honeycomb sheet metal for theXB-70 Valkyrie bomber.[citation needed]
A fused-quartzwindscreen andcanopy andcockpitrefrigeration system were designed and fitted, but were never tested in the environment for which they had been designed.[citation needed] The pilot was provisioned with a conventionalejector seat. All of the flight controls, along with elements such as theundercarriage and four-partair brakes, werehydraulically powered.[7] The main undercarriage elements retracted inwards to lie vertically within the fuselage aft of the mainspar, while the forward undercarriage retracted forwards into a space directly aft of the cockpit. The majority of the oval-shaped fuselage's internal volume was occupied by the fuel tanks; a large compartment forward of the wing housed the suite of electronic recording andtelemetry apparatus along with elements of the refrigeration system.[7]
Amongst the various stipulations of the specification was the requirement of engine installations which permitted the fitting of different air intakes, engines and propelling nozzles.[8] The Type 188 was originally intended to be powered by a pair ofRolls-Royce Avon engines, however, these were substituted for a pair ofDe Havilland Gyron Junior engines (each of which was half a ton lighter) in June 1957. This change of engines necessitated some configuration changes, including the mounting of the engines further forwards along with elongated nacelles and jet pipes.[7][9] The Gyron Junior was then under development for theSaunders-Roe SR.177 supersonic interceptor and incorporated a fully variablereheat arrangement, which achieved a smooth variation in thrust between dry and full reheat, so being one of the first engines in the world to give continuous variation in thrust from idle to max reheat.[10] This choice of powerplant resulted in the Type 188 having a typical endurance of only 25 minutes, not long enough to conduct the high-speed research tests that were required of it. Chief Test Pilot Godfrey L. Auty reported that while the Type 188 transitioned smoothly from subsonic to supersonic flight, the Gyron Junior engines were prone to surging beyond that speed, causing the aircraft topitch andyaw.[citation needed]
In order to solve the aerodynamic andflutter problems identified, a large number of scale models were produced and tested. Some of these models were mounted on convertedrocket boosters and used to conduct free-flight investigations, multiple such launches were conducted fromRAE Aberporth.[11] As a result of these tests, along withwind tunnel testing, various aerodynamic refinements and alterations were made to the Type 188's design. As a result, a largely rectangular wing plan was adopted between the engine nacelles alongside horn-balancedailerons on the compact outer wings; theall-moving tailplane was also raised to the top of thefin while thechord was also extended to accommodate single-engine failure during take-off.[7]
It was ultimately decided that there would be three aircraft built, one being a static test frame while the other two (constructor numbers13518 and13519) would be used for flight testing.[7] On 4 January 1954, under contract numberKC/2M/04/CB.42(b), theserial numbersXF923 andXF926 were given to the two aircraft. To support the development of the Avro 730 Mach 3 reconnaissance bomber, another three aircraft were ordered (Serial NumbersXK429,XK434 andXK436). However, this follow-up order would be eventually cancelled shortly after the Avro 730 programme was itself terminated during 1957 as part ofthat year's review of defence spending. Despite this, the Type 188 project was continued for the time being as a high speed research aircraft.[1][7]
During May 1960, the first airframe was delivered to theRoyal Aircraft Establishment at Farnborough, where it underwent a series of structural tests, both heated and unheated, before it was transferred toRAE Bedford. On 26 April 1961,XF923 undertook the firsttaxiing trials, after which it was promptly put through extensive pre-flight testing.[7] Due to problems encountered with the initial design of the intake, themaiden flight of the Type 188 did not take place until 14 April 1962.[4][6]XF923 was intended to remain with Bristol for its initial flights and evaluation before turning it over to the MoA.XF926 had its first flight, powered byXF923s engines, on 26 April 1963;XF926 was given over to RAE Bedford for its flying programme.[4][7]
Across 51 flights, the Type 188 reached a top speed of Mach 1.88 at 36,000 ft (11,000 m).[2] The longest subsonic flight lasted only 48 minutes, which was largely due to 70 percent of the aircraft's total fuel capacity being consumed just to attain its operational altitude.[1]
In September 1962, the first prototype made its first public appearance, being displayed on both the ground and in the air at that year'sFarnborough Air Show.[7] During that same year, the aircraft was seen in the filmSome People.[12]
Measurements during testing were collected and, in addition to being recorded onboard, weretransmitted to a ground station for live review as well as being recording and subsequently analysed.[13] The ground station was typically manned by both an engineer and a "ground pilot"; the extent of the flight information transmitted permitted the ground pilot to comprehensively advise the pilot of the aircraft in real time, although it was convention for only key information to be communicated as such to avoid excessive distraction to the pilot flying.[7]
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Flight testing of the Type 188 encountered a number of problems, perhaps the principal being that the fuel consumption of the Gyron Junior engines used did not permit the aircraft to fly at high speeds long enough to evaluate the "thermal soaking" of the airframe, which was one of the main research areas that the Type 188 had been built to investigate. Combined with fuel leaks, the inability to reach its design speed of Mach 2 and atakeoff speed at nearly 300 mph (480 km/h) severely compromised the flight testing phase of the project.[2] Nonetheless, although the Type 188 programme was eventually abandoned, the knowledge and technical information gained was put to some use for the futureConcorde program. The inconclusive nature of the research into the use of stainless steel led to Concordes being constructed from conventionalaluminium alloys with a Mach limit of 2.2. Experience gained with the Gyron Junior engine, which was the first British gas turbine designed for sustained supersonic operation, additionally later assisted with the development of the Bristol (later Rolls-Royce)Olympus 593 powerplant, which was used on both Concorde and theBAC TSR-2.[1]
During early 1964, it was announced that all development activity on the Type 188 was to be terminated. The final flight ofXF926 took place on 12 January 1964. In total, the project cost £20 million.[3] By the end of the programme, considered the most expensive to date for a research aircraft in Britain, XF923 had to be "cannibalised" in order to keep the other airframe flightworthy.[4][14]
In April 1966, both Type 188 fuselages were transported to theProof and Experimental Establishment atShoeburyness, Essex to act as targets for gunnery trials, but during 1972,XF926 was dismantled and moved toRAF Cosford (without its engines) to act as instructional airframe 8368M, and is preserved at theRoyal Air Force Museum Cosford inShropshire.[1]XF923 was subsequently scrapped atFoulness.[3]
Data fromThe World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters,[3]Bristol Aircraft since 1910[15]
General characteristics
Performance
Bristol 188XF923 was prominently featured inSome People (1962), a feature film primarily shot in Bristol.[1]
Aircraft of comparable role, configuration, and era
