The First French Jets
Beginning in 1938 and 1939, the French
Armee de l'Aire sharply increased their interest in developing turbojet engines in light of German and Italian research into alternate propulsion methods. Development of new engines was given to four French companies, with orders to research and develop different aspects of the technology. Unlike the situation which developed in Germany, Britain, and other early turbojet developers, the French turbojet research lacked the presence of iconic engineers like Frank Whittle and Hans von Ohain, who claimed patents and places in the history books. Instead, French research tended to emanate from project teams composed of multiple engineers, working and designing in concert. Although several names of the more productive and knowledgeable project leaders have survived, the majority of work was done by engineers and researchers who would remain relatively unknown through the rest of their lives.
The Problem of Propulsion
Hispano-Suiza, at that time France's largest aircraft-engine manufacturer, hired Dimitri Sensaud de Lavaud, the creator of the first French turbo-jet engine, and began work on turbo-compound piston engines. These engines used a gas recovery turbine to draw energy from the engine exhaust. Efforts largely focused on the 24-cylinder inline Hispano-Suiza 24H. By mid 1943, continued development resulted in the 24H Composé engine, which developed 3,500 horsepower. The first 24H Composé engine was actually built by Farman's engine-manufacturing division (which had close ties to Hispano-Suiza) and flew in July with the experimental Farman Belphegor, which challenged altitude records. Hispano-Suiza simultaneously worked on true turbojet technology for other non-aero applications. However, despite their work with turbojet technology, Hispano-Suiza never manufactured a turbojet engine of their own design during the 1940s..
Turbomeca, a company founded in 1938 by Joseph Szydlowski and André Planiol, worked very closely with Hispano-Suiza and Gnome-Rhone to develop superchargers for aircraft engines, and despite the company's youth, they were quickly included in the effort to design a French turbojet engine. The company grew massively between 1938 and 1942, as it was the only substantial French provider of turbochargers and superchargers, supplying both Hispano-Suiza and Gnome-Rhone. Although Turbomeca's R&D division was small, it was dynamic and inventive, and focused on small-scale turbojet applications with knowledge gleaned from their contacts with Gnome-Rhone and Hispano-Suiza. Turbomeca's assistance to Hispano-Suiza was critical to the company's successful creation of the HS-24H Composé, and by 1945 Turbomeca had prepared innovative designs for turbojet and turboprop engines. They would soon become a world leader in the development of the turbojet.
To the firms of Gnome-Rhone and the much smaller Rateau-Anxionnaz was entrusted the job of designing and building turbojets for military use. Rateau-Anxionnaz, which manufactured parts for steam turbines for Indret, had a small advantage, particularly due to the presence of engineer Rene Anxionnaz. Anxionnaz began work on a turbojet design called the A.60, which used a centrifugal compressor like in the earliest designs fielded by Germany and Britain. The A.60, which first ran in late summer of 1941, was designed to provide 1,600 KG thrust, but in practice it never gave more than a thousand kilos. The A.60 additionally suffered, particularly in its earliest days, from runaway combustion, where the engine sucked in fuel at a terrific rate and raced the engine to nearly explosive speeds, and from an unfortunate tendency to catch fire. Through 1942 and 1943, Anxionnaz worked to overcome the limitations of the engine design, but it would still be the A.60 that powered France's first jet flight, made with the Bloch MB.1000 Triton. Persisting in his development, Anxionnaz eventually produced an updated variant of the A.60, designated as the A.62, which finally achieved the goal of 1,600 kgf. The A.62 would power France's second jet, the Dewoitine D.800 Flèche, in early 1944. The A.62 was still seen as a flawed engine, however, and in December 1943 Anxionnaz petitioned the
Service Technique de l'Aéronautique, which oversaw the development programs for the French Ministry of Defense, to allow them to cease development of the A.62 in order to develop a clean sheet design. The STA agreed to this proposal with the caveat that the A.62 still had to be produced through 1944, in order to support aircraft manufacturers. Rateau-Anxionnaz quickly designed the A.65, which reached the test bench in late January 1944. The A.65 was of a novel design with a single axial stage and a single centrifugal stage compressor (a design mimicked by Turbomeca later). The A.65 was the first French turbojet to incorporate a 'réchauffe' or postcombustion stage component to the engine, although this was not added until later versions.
Although Gnome-Rhone had significantly greater research and development resources than Rateau-Anxionnaz, the larger company proceeded at a slower pace. In portioning out the French development efforts, the
Service Technique de l'Aéronautique had given Gnome-Rhone the task of developing axial turbojets, while Anxionnaz and Turbomeca developed centrifugal turbojets. The size of Gnome-Rhone's R&D department made the STA feel the larger company had a better ability to handle an advanced and long-term development program. Gnome-Rhone harvested extensive contacts within allied powers, particularly within Atlantis. The Atlanteans, who flew their first turbojet-powered aircraft in March 1942, had worked extensively on axial-layout turbojets through the work of Dr. Menelaus Crius. Gnome-Rhone eventually unveiled their first turbojet, nicknamed the 'Curtana', in November 1943. Despite STA's attempts to prod development along at a faster pace, Gnome-Rhone took their time for development. As a result, the first aircraft designed to be powered by the Curtana engines, the VG.640 Graoully, was significantly delayed in delivery. However, despite their tardiness, Gnome-Rhone knew their business and eventually developed the Curtana into one of the most potent and reliable engines of the early jet age.
The Problem of Airframes
STA's primary goal in developing a French turbojet was always to use it to place as the propulsion unit of a new fighter. Beginning in the mid 1930s, the French Air Force became concerned at the increase of operating speeds and altitudes of fighters and bombers. In order to accomplish these higher performance figures, piston engines were growing in size and weight, with the accompanying growth of airframe design. The Armee de l'Aire's interest in the turbojet was primarily as a way to achieve higher performance figures than were believed to be possible with pure piston-engine aircraft.
One early possibility which the French investigated was the ramjet engine of Rene Leduc. France held a substantial lead in ramjet development, and there were proposals to field groups of ramjet-powered interceptors which could climb quickly to intercept even the fastest of enemy bombers. The ramjet's greatest flaw was that it required external air-flow to start the engine: all of the ramjet flights had to be accomplished by carrying the testbed aloft on a mothership. This was clearly not a feasible solution, and thus the French turned to turbojet engines.
At the beginning of the project, numerous French aircraft manufacturers desired to undertake research and development into jet aircraft - so long as the French government paid the bill. Although the STA awarded funds for research and development of new types, they became increasingly strict with their requirements. Five companies eventually emerged at the head of the development groups. Breguet (which merged with Nord in March 1942 to become Breguet-Nord) quickly established themselves as one of the earliest partners of the STA, building the Leduc ramjets. However, Breguet-Nord evinced little interest in developing fighter aircraft. Similarly, Lioré et Olivier preferred to work on larger designs.
Most early jet fighter design therefore occurred at
Constructions Aéronautiques Émile Dewoitine,
Société des Avions Dassault (formerly
Société des Avions Marcel Bloch), and the government-owned
Arsenal de l'Aéronautique. All three companies presented their initial designs to the STA and the Armee de l'Aire in 1943, together with estimated timelines for development and production. Although the Armee de l'Aire had consciously pursued a policy of standardization with regard to its fighter arm, picking a single design and then producing massive quantities, this policy was temporarily and intentionally abandoned with the early jets. Simultaneous development and manufacture of several types, with production to occur in low quantities, would ideally provide the French air force with operational experience, as well as fallback options in case a design should fail.
Dewoitine's D.800 Flèche ("Arrow") was the first jet fighter turned over to ONERA for testing, arriving at the CEV testing grounds in January 1944. Three initial weeks were spent with inspections and taxi trials. The D.800's first flight was delayed a day due to weather, but occurred on February 11th, 1944. It was immediately obvious that performance, particularly speed, was disappointing: the D.800 struggled to outrun an Arsenal VB.20 chase plane, only pulling ahead above eight thousand meters altitude. The second flight was marred when the A.62 engine caught fire during preparations for take-off, and the test pilot broke his wrist when he was forced to jump out of the aircraft. Although the aircraft was not permanently damaged, it was an inauspicious start. Nevertheless, ten pre-production aircraft were ordered with the hope that performance would improve after further development. More production aircraft would eventually be ordered, sufficient to equip a
Groupe de Chasse, but the Flèche never proved to be a success story.
Arsenal's entry into jet power was more fortuitous. Arsenal had previously made their name with the VG.30 series propeller-driven fighters, which were then followed by the even more successful VG.60 and VG.64. The VG.60 was lightweight, easy to manufacture, friendly to fly and competitive with the best foreign air forces had to offer. Arsenal took a low-effort approach to jet design: they simply redesigned the tricycle-gear VG.64 to mount a single Gnome-Rhone Curtana 1C turbojet in the aircraft's nose, with the turbojet exhaust venting underneath the aircraft's belly. Almost all other features of the original VG.64 were retained. This low-effort approach yielded ironically good results: the resulting VG.640 Graoully actually had a higher top speed and better maneuverability than the Dewoitine, although it suffered from issues with range. Additionally, as so many parts from existing aircraft had been retained, the cost of the VG.640 was significantly lower. Although the first VG.640 airframe was completed in December of 1943, Gnome-Rhone did not deliver a completed TRAC-1C engine until mid March, and flight testing did not begin until April. Seventy-six were immediately ordered, and the numbers increased quickly. Production, however, proved to be problematic: through 1944 and 1945, all French aircraft engine manufacturers had difficulty keeping up with demands. Completed aircraft often waited months to receive their engines.
Although the Graoully had several advantages over the Flèche and was produced in larger quantities, the Armee de l'Aire used it more as a sort of advanced trainer, building a corps of pilots experienced in jet operations. The Graoully was out of 'frontline service' before the end of 1945, although most planes remained in a training role for some time afterward. Others were transferred to foreign air forces.
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Dewoitine D.800 Flèche
General characteristics
Crew: One
Length: 9.69 m (31ft 9.5in)
Wingspan: 11 m (initial version, rounded wingtips) or 10.50 m (final version, squared wingtips) (36ft 11in)
Height: 3.39 m (11ft 1.5in)
Wing area: 19,70 m²
Empty weight: 2,358 kg (5,198 lb)
Max takeoff weight: 3,600 kg (7,937 lb)
Powerplant: 1 × Rateau A.62 centrifugal turbojet, 15.7 kN (1,600 kgf / 3,527.4 lbf)
Performance
Maximum speed: 720 km/h (447 mph)
Range: 900 km (559 mi)
Service ceiling: 15,500 m (50,855 ft)
Rate of climb: 20.8 m/s (4,094 ft/min)
Power to weight ratio: 0.444 lbf/lb at loaded weight
Wingloading: 182.7 kg/m² / 37.43 lb/ft²
Armament
Guns: 4 × 23 mm Hispano-Suiza HS.406 cannon with 125 rounds per gun
Notes
This is the historical FMA Pulqui I, which was designed in Argentina by Emil Dewoitine and some Argentine co-workers. Used with Hood's permission.
First flight February 1944, entry into squadron service around September or so. Probably retired from service by 1946-47.
Estimated quantity manufactured: between 50-100, no more. Production will probably run from July to December of 1944, after which it will be ended.
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Arsenal VG.640 Graoully fighter
Specifications
Wingspan: 10.7 m (35.1 feet)
Length: 9.06 m (29.7 feet)
Height: 3.14 m (10.3 feet)
Wing Area: 18.8 m² (202.36 ft²)
Empty weight: 2,500 kg (5,511 lbs)
Loaded Weight: 3,319 kg (7,317 lbs)
Engine: 1 × Gnome-Rhone Curtana TRAC-1C axial turbojet 9 kN (918 kgf / 2,023 lbf thrust)
Crew: 1 (pilot)
Performance
Max speed: 750 kph (466 mph) @ 9,000 meters
Range: 550 km (314 miles)
Service ceiling: 12,250 m (40,190 ft)
Rate of climb: 20.5 m/s (4035 ft/min)
Power to weight ratio: 0.276 lbf/lb at loaded weight
Wingloading: 176.5 kg/m² / 36.2 lb/ft²
Armament
- 2 × 23 mm HS.406 with 90 rounds in nose
Variants
- VG.640: Single-seat fighter
- VG.640T: Twin-seat advanced trainer
Notes
This is based off the Russian Yak-15/Yak-17 concept.
First flight May 1944, entry into service October/November 1944.
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OOC Comments: Basically, I view both of these aircraft as failures, or perhaps partial successes. They'll look good in press photographs and overflights during Bastille Day, but it should be fairly obvious, even to foreign observers, that the French are struggling a bit with their first jets.