In his fascinating interview with Hush-Kit in May 2012, supercar designer Peter Stevens theorised on the often close relationship between aircraft and automobile design: “In aircraft terms all cars can be described as being reliant on ‘low speed aerodynamics’, but the actual shapes are often taken from very high speed aircraft”.

One of the most blatant examples of this idea at work was American car designer Harley Earl’s astonishing Firebird series of concept cars for General Motors (GM) during the 1950s. Powered by gas-turbine engines developed by Emmett Conklin and bristling with fins, bubble canopies and other aeronautically-inspired refinements, the Firebirds represented the high-point of America’s obsession with the jet age.

Earl was no stranger to using aircraft as inspiration — his Le Sabre concept car of 1951 was, as the name suggests, directly influenced by North American’s F-86 Sabre jet fighter, then fighting it out with Soviet MiGs over Korea. He had also long admired the unorthodox twin-boom layout of Lockheed’s World War Two-vintage P-38 Lightning, reflected in the designer’s fishtail fenders for later GM products. Earl was fascinated by the impression of speed that aircraft imparted, fighter aircraft in particular adhering to his concept of cars looking long and low, alert, ready to pounce.

Having introduced sharply-swept fins and wraparound windshields, both a prevalent part of contemporary fighter design, on the Le Sabre, Earl felt compelled to push further into the realms of the fantastic, often making almost impossible demands on his long-suffering technical team in the interests of pushing the envelope of American automobile design.

Reportedly, Earl was aboard an airliner during one of his frequent trips across the USA in the early 1950s when he read a short article in an in-flight magazine on the futuristic Douglas A4D Skyray, which made its first flight in January 1951. Earl was fascinated by the new Navy fighter and stared at the photographs in the article for more than an hour. Remarking that it was “a striking ship”, he tore the page from the magazine and put it in his inside pocket before settling into deep thought. When his travelling companion asked whether he was thinking of next year’s model and what it might be, Earl paused for a moment before slapping his breast pocket and saying “I have it right here”. Earl later recalled: “I was only answering the banter in kind. Then bingo, I decided I had kidded myself into something”.

Design and construction of the first Firebird began in 1953, the idea being to create a complete rolling laboratory in which state-of-the-art technology could be tested in real road conditions. It was also a clear opportunity for GM to showcase the extremes in technology and design that it was capable of. Given the company designation XP-21, the single-seat Firebird I was the first American car to be powered by a gas turbine engine, in the form of the 370 h.p. Whirlfire GT-302. Arguably the single most impractical car ever devised, the Firebird I comprised a bullet-shaped fibreglass fuselage with a single fin and short rounded delta “wings” (as on the Skyray), the driver being accommodated in a fighter-style cockpit with a bubble canopy. Flaps were also incorporated for braking purposes — another lift from aeronautical design. The car was driven by Conklin and racing driver Mauri Rose and found to be largely satisfactory, despite issues with noise, exhaust overheating and, unsurprisingly, extremely high fuel consumption.

Earl’s second Firebird, designated XP-43, was intended to parlay the lessons learned with the Firebird I into a more practical four-seat family car. With its distinctive double air intakes at the front, high bubble canopy and fin, the Firebird II was intended to be a component of GM’s “Safety Autoway of Tomorrow”, a rapid transit system which would take advantage of an “electronic brain” in the car, which received signals from a metallic conductor buried in the road, the magnetic device creating a form of autopilot for cars. The boffins at GM worked hard to get the system working and eventually conducted successful tests of what the company dubbed the “dream highway”. The Firebird II was the first car to have its entire exterior bodywork constructed from titanium, then being used in the construction of the USA’s state-of-the-art fighters such as the McDonnell F-101 Voodoo and Lockheed’s F-104 Starfighter — another of Earl’s appropriations of contemporary aeronautical techniques.

If the Firebird II reflected fighter aircraft design in the mid-1950s, the last  — and most extravagant — of the Firebirds anticipated the cutting edge of the next generation of American warplanes, typified by Republic’s super-sleek F-105 Thunderchief, which entered US Air Force service in mid-1958. While GM’s engineers were perfecting the “electronic chauffeur”, Earl and his team were going for broke with a design that incorporated no fewer than seven wings and fins protruding from a science-fictionesque wedge-shaped main body.

Promotional material of the time dispensed with any pretence of subtlety and announced that the new Firebird would be “an entirely different kind of car, in which a person may drive to the launching site of a rocket to the moon”, the aeronautical terminology being supercharged to include the rapidly escalating space race. The new car, which incorporated double bubble canopies, cruise control and air-conditioning, was to be fitted with an extension of the Firebird II’s “ping-pong ball” control system, known as Unicontrol, in which steering, acceleration and braking would be performed by means of a single control stick, again echoing fighter cockpit design.

The initial tests of all three Firebirds were referred to as “first flights”, that of the Firebird III taking place at GM’s Desert Proving Ground in Phoenix, Arizona, in August 1958, the machine subsequently undergoing extensive trials in a windtunnel, as used for testing aircraft.

Publicly unveiled at GM’s 1959 Motorama show in New York City and Boston (actually held in October 1958), the Firebird III was a hit; the two-seat rocket-ship of the road fired the imaginations of the young and old alike. As on the Firebird II, Earl had sought to exploit aerodynamic braking in the form of air brakes, which emerged from flat panels in the Firebird III’s main body. The 225 h.p. Whirlfire GT-305 engine provided propulsion power only, a separate 10 h.p. two-cylinder powerplant being installed to drive the electrical and hydraulic accessories.

The Firebird III was not just a hit at the car shows; in April 1959 it was exhibited at the World Congress of Flight in Las Vegas, its space-age looks fitting right in with the highly advanced military hardware on view at nearby Nellis AFB.

The Firebirds were never seriously intended to be put into production, however earnest the brochures of the time were in suggesting otherwise, and although a Firebird IV ground-effect machine was built in mock-up form, GM decided that the III was the end of the line for the ambitious space-age Firebirds. The name, however, lived on in a series of Pontiac “ponycars” from 1967.

All three Firebirds still survive and have been acquired by GM, which aims to restore them to roadworthy status and possibly tour them at some stage. Happily, car designers are still very much taking cues from aeronautical developments, as Peter Stevens explained in his Hush-Kit interview: “I do think that designers are looking at things like the F-117 stealth fighter for inspiration; the Lamborghini Aventador is a good example of this trend”. Long may it continue.

By Nick Stroud, Editor of The Aviation Historian

The interview of Peter Stevens by Joe Coles can be found here: 

Follow my vapour trail on Twitter: @Hush_kit