The Bristol 188, known as ‘The Flaming Pencil’, was an experimental aircraft commissioned by the British government with the sole purpose of investigating the conditions of supersonic flight, which had been proven possible in 1947.
British juggernauts Bristol Aeroplane Company were somewhat unrealistically expected to create one of the fastest airplanes in the world just to meet this ambitious requirement.
Although many lessons would be learnt from the decade-long 188 program, it would also prove to be a reality check, and a case study in the difficulties that inevitably arise from efforts to apply groundbreaking scientific discoveries into modern technological uses.
In October 1947, US Air Force Captain Chuck Yeager broke the sound barrier for the first time ever while piloting the X-1 rocket plane, produced by Bell Aircraft Company, over Rogers Dry Lake in southern California.
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With his speed dial exceeding 662 mph at 40,000 feet, he paved the way for supersonic flight, a feat previously deemed impossible by many skeptical commentators, who believed it would tear any aircraft apart.
Following Yeagers’ demonstration that it was indeed possible for humans to travel beyond the limits of sound, the scientific community was eager to learn more about flying conditions at the supersonic level.
By the early 1950s, the effect of such high velocities on the structure of an aircraft was still relatively unknown. It prompted the British government to challenge its aeronautical industry to build them an aircraft that could help researchers shed some light on this new and exciting frontier of air travel.
In order to examine the kinetic and heating effects of supersonic speed on airplane structure, Specification ER.134D called on manufacturers to produce an experimental air vehicle that could maintain a speed of Mach 2.75 for long periods of time.
It would be the fastest airplane in the world after the North American X-15 space plane. Policymakers were to use the findings to help support the development of the Avro 730 Bomber, another ambitious project, which was forecast to fly at Mach 2 speed and above.
Several manufacturers vied for the contract, designated 6/Acft/10144, including English Electric who submitted plans to make another version of the Lightning called the P.6. After a lengthy competition, it was awarded to the Bristol Aeronautical Company in February 1953 which was tasked with creating 3 prototypes.
Only the XF923 and the XF926 were earmarked to fly, with the remaining model planned only to be a test bed stationed permanently on the ground.
Numbering their new project 188, a further 3 Bristols were also ordered, given the serial numbers XK429, XK434, and XK436, but they were soon cancelled after the discontinuation of the Avro program in 1957.
Under the watchful guidance of veteran aircraft technician Archibald Russell, who would later receive a knighthood for his contribution to the Concorde successor, the program commenced in 1954.
The first challenge that Bristol faced was finding a suitably strong material that could withstand the onslaught of supersonic speed.
After a long search, they settled on F.V.520 hardened stainless steel which could resist heat of up to 500 degrees Celsius. Engineers turned to the latest approaches, performing puddle-welding, which utilized inert argon gas to fuse the steel to make panels.
Yet, Bristol’s overriding desire to use the most up-to-date methods would be responsible for a series of delays that plagued them from the very outset, as puddle-welding proved less effective than previously hoped.
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They would also have to completely re-design the wings after aerodynamic difficulties were found during model testing, setting them back even more.
In addition, design changes to the engine further halted proceedings. Bristol was forced to look for a replacement after its Rolls-Royce Avon R.A.24R engines, also to be used in the Avro bomber, were scrapped following the termination of the Avro project in 1957.
Multiple De Havilland PS.50 ‘Gyron Junior’ engines were instead implemented, in a switch that would ultimately be responsible for the 188’s downfall.
It would take until May 1960 for the first airframe to be delivered to Farnborough, its structural qualities tested there before it was moved on to the Royal Aircraft Establishment in Bedford.
Engine trials for the XF923 commenced the next year in April, unveiling further issues with the intake and afterburner components. After this was fixed, the Bristol was ready for its maiden voyage set for April 1962.
The Bristol 188, weighing 37,527Ibs and possessing a span of 35 feet and 1 inch, had a long cylindrical shape ending with a pointed nose and a large fin located on its back.
Its frontal area was reduced with a long slim fuselage, as were the wing sections which were made extremely thin at 4%, each housing a small engine bay.
The aircraft’s outer wings were so sharp that special gloves had to be made in order to protect the hands of the employees working on it, who affectionately christened it ‘The Flying Pencil’ after its sleek characteristics.
Alongside its slender wings, the Bristol 188 was outfitted with a wide array of advanced features designed to diminish heat intake.
Its fuselage panels were made from a mixture of titanium and stainless steel as opposed to conventional aluminium, the windscreen and canopy were lined with quartz, and it was fitted with a refrigeration system in the cockpit that could cool down the craft when necessary.
Finally, in April 1962 the XF923, commanded by Bristol Chief test pilot Godfrey L. Auty, took to the skies for the first time without incident, taking off from Filton and landing safely at Boscombe Down.
In September it made its first public debut, being exhibited at the Farnborough Air Show for four consecutive days to a rapturous response.
The XF926 started its life in the air less auspiciously in April 1963, being escorted by a Hawker Hunter T-7 for its first flight.
The 51 flights of the XF923 revealed some major flaws. Although the Gyron Junior gas turbines it was fitted with provided ample enough power, they guzzled so much fuel that the craft could only travel at Mach 1.88 speed for only 25 minutes, not nearly enough time to perform adequate high-speed tests and more importantly not within the desired Mach 2 range set out by the British government.
In fact, the longest flight of the Bristol clocked in at a mere 48 minutes after 70% of the fuel had been burnt lifting it to operational altitude.
It meant that they could never properly analyse some of the heat reduction innovations, such as the quartz-lined windscreen and canopy as well as the cockpit refrigeration system.
In addition, Pilot Godfrey Auty would praise the craft for its smooth transition between subsonic and supersonic levels, but criticize its dangerous tendency to jerk between pitch and yaw directions because of unpredictable surges in speed due to engine malfunctions.
The only facet of the program to not disappoint was the trailblazing flight data collection system, around 30 years ahead of its time, which for the first time was able to send flight data to a command centre electronically for near-instantaneous information evaluation.
Personnel on the ground were also helped by the addition of a second cockpit commanded by a co-pilot, who could remotely control a lot of the aircraft’s functions, allowing his commanding officer to focus more on manoeuvring.
The last journey of the Bristol 188, with the XF926 edition, was in January 1964 and was only made possible by the sacrifice of the XF923, which was constantly scavenged for spare parts. Project leaders decided that the cost of redesigning the engine bays and intakes so the Gyron Juniors could be replaced was simply too much.
In addition, by the 1960s, more research into supersonic technology was not needed after the significant advances of the 1950s.
Indeed, by the time the 188 made its first foray into the skies, the Mach 2 Lightning had already entered into service with the RAF.
In April 1966 the fuselages of both were uninstalled and transported to the Proof and Experimental Establishment in Shoeburyness, Essex, to be used as weapons-testing targets. Later in 1972 the XF926 was fully dismantled and sent to RAF Cosford, where its airframe was used for educational purposes thereafter as instructional airframe 8368M, before being later moved to the RAF Cosford Museum where it can be found today.
After a brief cameo in the 1962 film `Some People`, featuring footage of one of its test flights, the XF923 met a less illustrious end, being pawned for scrap metal at Foulness.
The knowledge gained from the Bristol 188 would be an important stepping stone, informing much of Bristol’s efforts at creating a supersonic airliner for their Concorde program alongside French firm Sud Aviation in 1962.
The shortcomings of the Gyron Junior engine also greatly influenced the development of Bristol’s Olympus 593 powerplant, which was installed on the Concorde as well as the BAC TSR2.
Moreover, thanks to the insights provided, it was decided that another airplane, the Bristol Type 223, should not be fashioned with stainless steel, the 188 illustrating that such a process was too expensive and ineffective.
In the end, the Bristol 188 was a failure, but a necessary bridge to the glory of the Concorde program, which would emblazon Bristol’s name into the annals of aviation history.
- Crew: 1
- Length: 77 ft 8 in (23.67 m)
- Wingspan: 35 ft 1 in (10.69 m)
- Height: 12 ft 0 in (3.66 m)
- Powerplant: 2 × de Havilland DGJ.10R Gyron Junior afterburning turbojets engines, 10,000 lbf (44 kN) thrust each
- Maximum speed: 1,043 kn (1,200 mph, 1,932 km/h)