Bristol 188

Le Bristol 188 raconté sur Wikipedia; en anglais :

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The Bristol 188 was a [Vous devez être inscrit et connecté pour voir ce lien] research [Vous devez être inscrit et connecté pour voir ce lien] built by the [Vous devez être inscrit et connecté pour voir ce lien] in the 1950s.

Its length, slender cross-section and intended purpose led to its being nicknamed the "Flaming Pencil".

Design and development

The aircraft had its genesis in [Vous devez être inscrit et connecté pour voir ce lien] 330 for a high speed (Mach 3) [Vous devez être inscrit et connecté pour voir ce lien] aircraft, which eventually developed into the [Vous devez être inscrit et connecté pour voir ce lien].

As the 730 was expected to operate at high speeds for extended periods of time, more data was needed on high speed operations, leading to Operational Requirement ER.134T for a testbed capable of speeds greater than [Vous devez être inscrit et connecté pour voir ce lien].

The aircraft was expected to run at these speeds for extended periods of time, allowing it to study [Vous devez être inscrit et connecté pour voir ce lien] on such an aircraft.

The aircraft was expected to spend a considerable amount of time with a skin temperature around 300 Celsius.

Several firms took interest in this very advanced [Vous devez être inscrit et connecté pour voir ce lien] and the eventual contract (6/Acft/10144) was awarded to Bristol Aircraft in February 1953.

Bristol gave the project the type number 188, of which three aircraft were to be built, one a pure test bed and the other two (constructor numbers 13518 and 13519) for flight testing.

Under contract number KC/2M/04/CB.42(b) [Vous devez être inscrit et connecté pour voir ce lien] XF923 and XF926 were given on 4 January 1954 to the two that would fly.

To support the development of the [Vous devez être inscrit et connecté pour voir ce lien] Mach 2 reconnaissance bomber, another three aircraft were ordered
(Serial Numbers XK429, XK434 and XK436).

The follow-up order was cancelled when the Avro 730 programme was cancelled in 1957 as part of [Vous devez être inscrit et connecté pour voir ce lien].

The 188 project was continued as a high speed research aircraft.

Steve Lane. Taken at RAF Museum Cosford, on 1st March 2007. URL - [Vous devez être inscrit et connecté pour voir ce lien]

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The advanced nature of the aircraft meant that the construction methods had to be developed.

Several materials were considered for construction and two specialist grades of steel were selected: a [Vous devez être inscrit et connecté pour voir ce lien]-stabilized 18-8 [Vous devez être inscrit et connecté pour voir ce lien] and a 12%-[Vous devez être inscrit et connecté pour voir ce lien] steel used in gas turbines (Firth-Vickers.448).

These had to produced to better tolerances in sufficient quantities for construction to start.

The 12% [Vous devez être inscrit et connecté pour voir ce lien] with a [Vous devez être inscrit et connecté pour voir ce lien] centre was used for the construction of the outer skin, to which no paint was applied.

Riveting was a potential method for construction but the new [Vous devez être inscrit et connecté pour voir ce lien] technique using an [Vous devez être inscrit et connecté pour voir ce lien] gas shield known as [Vous devez être inscrit et connecté pour voir ce lien] was used.

There were long delays with the method and was less than satisfactory.

The [Vous devez être inscrit et connecté pour voir ce lien] company, provided substantial technical help and support to Bristol during this period; they produced major sections of the airframe as a subcontractor.

A fused-[Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] refrigeration system were designed and fitted but were never tested in the environment for which they had been designed.

The engine installations had to allow development of variable geometry intake systems.

These would permit maximum efficiency at across a range of supersonic speeds.

This had also led to the engines position on the wings rather than within the fuselage.

[Vous devez être inscrit et connecté pour voir ce lien] engines were initially selected to power the 188, but five engine combinations were evaluated:
two with [Vous devez être inscrit et connecté pour voir ce lien] 200s, two with the [Vous devez être inscrit et connecté pour voir ce lien] and one with an [Vous devez être inscrit et connecté pour voir ce lien], the last disintegrating on test.

Subsequently, in 1957, the final choice for the 188 was two 10,000 lbf (44 kN) [Vous devez être inscrit et connecté pour voir ce lien] Gyron Junior DGJ10Rs, developing 14,000 lbf (62 kN) of thrust on [Vous devez être inscrit et connecté pour voir ce lien] at sea level and 20,000 lbf (89 kN) at Mach 2 at 36,000 ft
(11,000 m).

The Gyron Junior was then under development for the [Vous devez être inscrit et connecté pour voir ce lien] supersonic interceptor and incorporated a fully variable reheat, from idle to full power, the first such application used in an aircraft.

Unfortunately this choice of powerplant resulted in the 188 having a typical endurance of only 25 minutes, which was too little time for any serious high speed research.

Chief Test Pilot Godfrey L. Auty reported that while the 188 transitioned smoothly from subsonic to supersonic flight,
the Gyron Junior engines were prone to surging beyond that speed, causing the aircraft to [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien].

In order to solve the aerodynamic and flutter problems, a large number of scale models were employed.

Mounted on converted rocket boosters, a number of models were launched from RAE Aberporth, for free-flight
investigation.

Bristol Type 188 on display at the RAF Museum Cosford on February 23,
2007. Photograph by Neil Tipton.

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Operational history

In May 1960, the first airframe was delivered to the [Vous devez être inscrit et connecté pour voir ce lien] at Farnborough for structural tests – loading tests both heated and unheated – before moving on to [Vous devez être inscrit et connecté pour voir ce lien].

XF923 undertook the first [Vous devez être inscrit et connecté pour voir ce lien] trials on 26 April 1961, although due to problems encountered, the first flight was not until 14 April 1962.

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, using XF923s engines, on 26 April 1963. XF926 was given over to RAE Bedford for its flying programme.
Over 51 flights, it managed a top speed of Mach 1.88 (2,300 km/h) at 36,000 ft (11,000 m).
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The longest subsonic Bristol 188 flight was only 48 minutes in length, requiring 70% of the fuel load to be expended to attain its operational altitude.

XF 926

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Measurements collected during testing were recorded onboard and transmitted to the ground station for recording.

The flight information transmitted meant that a "ground pilot" could advise the pilot.

The project suffered a number of problems; the main being that the fuel consumption of the engines did not allow 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 it was built to investigate.