The beautiful “Flaming Pencil”

by Dr. Marshall Michel
86th Airlift Wing historian

The Bristol 188, certainly one of the most beautiful aircraft ever made, had its genesis in 1952 when the British Ministry of Defense issued specification ER. 134T for a test aircraft capable of speeds of Mach 1.8 to Mach 2.5 to gather data for the development of the Avro 730, a Mach 2 reconnaissance bomber.

The 188, much to Bristol’s disappointment, would never be developed as a combat aircraft. But the contract called for three aircraft to be built, one a pure test bed and the other two for flight testing.

The Avro 730 was cancelled in 1957 as part of the notorious “Defense White Paper” that said, among other things, no new strategic supersonic fighters or defensive supersonic fighters would be built for the Royal Air Force. Surprisingly, Bristol was allowed to continue the 188 project because its potential Mach 2.5 speed was deemed “indispensable” for research purposes for supersonic transport aircraft.
The 188 promised to be an exceptional performer that would have twice the speed and altitude performance of any aircraft in the world. Additionally, the design was modular so it could be adapted to a number of systems and engines, and it had built-in systems to collect data during test flights and transmit it directly to a ground station for immediate evaluation.

The 188 was expected to fly at more than Mach 2 for extended periods of time to study kinetic heating effects on the aircraft, and at those speeds steel took over from aluminum alloys as the optimum airframe material. To protect the pilot against heat build-up, it also had a special cockpit refrigeration system.

To get the necessary stiffness and resistance to high temperature from kinetic heating, the 188’s unpainted outer skin was made from 12 percent stainless steel with a honeycomb center.

The stainless steel skin required a new arc welding technique known as “puddle welding,” but the new process took time to develop and caused delays in the aircraft’s construction. Additionally, stainless steel was very heavy and the 188 weighed 40,000 pounds.

When it was completed in 1960, the 188 was a stunningly-beautiful aircraft. It had a long, thin fuselage, an almost “T” tail and a pointed housing for a large drag chute in the tail. The two large engine nacelles were mounted on a very thin wing that was straight from fuselage to nacelle but almost triangular from nacelle to tip. The air intakes could be easily removed so alternate intakes could be installed for flight tests.

But what went inside the nacelles was a problem. Five engine combinations were evaluated and the final choice was two Gyron Junior PS.50 engines with fully variable afterburners that developed (for the time) the amazing thrust of 20,000 pounds at 36,000 feet. That was the good news – the bad news was that the PS.50 proved to be an incredible gas guzzler and left the 188 with a very limited time of flight.

The problems with construction with the new materials and the engines resulted in the date of the first flight being slipped from July 1958 to April 1960 and then even further, and the first aircraft was not delivered for structural tests until May 1960. The problems were hidden from the public, and in December 1960, a British newspaper began publishing articles about what was called the “Flaming Pencil” because the skin was expected to glow from the heat generated at top speed.

The first taxiing trials took place April 26, 1961, but the first flight did not occur until almost a year later  on April 14, 1962. Test pilot Godfrey Auty flew it for 22 minutes, reached a speed of Mach 1.88 at 36,000 feet and reported that the 188 transitioned smoothly from subsonic to supersonic flight. Nevertheless, Auty was voted by his contemporaries as “the test pilot most likely to eject this year.”

Once flying tests began in earnest, the 188 showed a number of problems, including fuel leaks and an inability 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. Normal flights lasted only 25 minutes from take off to landing, and 70 percent of the fuel was used just to attain its operational altitude. The 188’s longest flight was only 48 minutes, and it was entirely subsonic.

Though the 188 was eventually abandoned, the problems associated with the use of stainless steel led to Concorde being constructed from conventional aluminum alloys with a Mach limit of 2.2, and the experience with the Gyron Junior engine assisted with the development of the Concorde’s Rolls Royce Olympus power plant.
For questions or comments, contact Dr. Michel at