Arsenal VG-33

The Arsenal VG-33 was one of a series of fast French light fighter aircraft under development at the start of WWII, but which matured too late to see extensive service in the French Air Force during the Battle of France.

The original specification that led to the VG series was offered in 1936 in order to quickly raise the number of modern aircraft in French service, by supplying a "light fighter" of wooden construction that could be built rapidly in large numbers. The contract resulted in three designs, the VG-30, the Caudron C.714 and the Bloch MB-700. Prototypes of all three were ordered.
Named for engineer Michel Vernisse (V) and designer Jean Galtier (G), the VG-30 was all wooden in construction, using plywood over stringers in a semi-monocoque construction. The layout was conventional, a low-wing monoplane that bore a striking resemblance to the later Italian Macchi C.202. Armament consisted of a 20 mm Hispano-Suiza HS.404 cannon firing through the propeller hub, and four 7.5 mm MAC 1934 M39 drum-fed machine guns, two in each wing. 

The design was supposed to be powered by the Potez 12Dc flat-12 air-cooled inline engine, but this ran into development problems. The prototype was then fitted with a Hispano-Suiza 12Xcrs instead, and flew in this form in October 1938.

General characteristics
Crew: 1
Length: 8.55 m 
Wingspan: 10.8 m 
Height: 3.31 m 
Wing area: 14 m2 
Empty weight: 2,050 kg 
Gross weight: 2,655 kg 
Powerplant: Hispano-Suiza 12Y-31 V-12 liquid-cooled piston engine, 641 kW / 860 hp
Maximum speed: 558 km/h 
Range: 1,200 km 
Service ceiling: 11,000 m
Power/mass: 0.24 kW/kg 
Armament; 1 × 20 mm Hispano-Suiza HS.404 cannon + 4 × 7.5 mm mg

In order to find some solution to the engine problem, the VG-31 was to use the 632 kW (860 hp) Hispano-Suiza 12Y-31 and the VG-32 the Allison V-1710C-15. The VG-31 flew in 1939 and proved to have excellent performance. The prototype VG-32 was completed in 1940 and awaiting its test flight when it was captured by the advancing German forces at Villacoublay.

The VG-33 was a modified version of the VG-31 using the same 12Y-31, and first flew on April 25, 1939. It had surprisingly good performance of 560 km/h, and was ordered into production with a contract for 220 aircraft in September, later raised to 1,000. Production didn't take long to start, but most of the airframes never received engines and sat at the factory when it fell to the Germans.

Further developments continued while the VG-33 production started. The VG-34 mounted the newer 688 kW (935 hp) 12Y-45, the VG-36 used the 735 kW (1,000 hp) 12Y-51 originally intended for the VG-35, and introduced a new streamlined radiator bath that looked similar to the one on the P-51 Mustang. Single prototypes of all three were built and flown in early 1940. The VG-37 was an extended-range version of the -36, while the VG-38 was to have used the 12Y-77, but neither was built.

The last in the series was the VG-39, originally powered by the new 882 kW (1,200 hp) 12Y-89 using an extension shaft on the propeller to streamline the nose profile, giving the plane an excellent speed of 625 km/h (388 mph) even when loaded down with two more machine guns. The actual production version was to have been the VG-39bis, powered by the new 1177 kW (1,600 hp) Hispano-Suiza 12Z-17, using the streamlined radiator intake design from the VG-36.

Two more designs were projected, both based on the VG-39bis airframe. The VG-40 mounted the Rolls-Royce Merlin III and the VG-50 the newer Allison V-1710-39. Neither was built.

Although using the same engine and being lighter, the VG-33 was capable of the same speed as the Dewoitine D.520. Somewhat under-armed compared to the Messerschmitt Bf 109, it matched it in terms of speed and maneuverability, but as was the case with the D.520, due to the limitations of the supercharger in use at the time, this could be achieved only below 5,000 m. In any event, plagued by continued production problems the aircraft never took part in combat. 

Only 19 of about 40 completed aircraft were actually received by the Armée de l'Air, while at the time of Armistice about 160 were close to completion. Only two machines ever flew in an active group - the GC 1/55 which began life under chaotic conditions four days before the capitulation – but did not have an opportunity to prove its capabilities. The Luftwaffe confiscated twelve VG-33s, perhaps for training use.

Variants
VG-30 - The original powerplant was the Potez 12Dc flat-12 air-cooled inline engine, but the prototype was fitted with a Hispano-Suiza 12Xcrs, and flew in this form in October 1938.
VG-31 - Hispano-Suiza 12Y-31 powered prototype.
VG-32 - Allison V-1710C-15 powered prototype.
VG-33 - First production model with Hispano-Suiza 12Y-31 engine (160 near completion at Fall of France. Unknown number completed.)
VG-34 - 697 kW (935 hp) Hispano-Suiza 12Y-45 engine. 360 mph (600 km/h). Prototype only.
VG-35 - VG-33 variant with newer engine. One built.
VG-36 - 746 kW (1,000 hp) Hispano-Suiza 12Y-51 engine. Prototype only.
VG-37 - Extended-range version of the VG-36. Not built.
VG-38 - projected for Hispano-Suiza 12Y-77 engine. Not built.
VG-39 - 954 kW (1,280 hp) Hispano-Suiza 12Z engine. 393 mph (655 km/h). 6 7.5 mm MAC 1934 machine guns. Prototype only.
VG-39bis - proposed production version powered by a Hispano-Suiza 12Z-17.
VG-40 - projected variant powered by a Rolls Royce Merlin III.[1]
VG-50 - projected variant powered by an Allison V-1710-39. (N.B. The designation VG 50 was also used for a projected four-engined trans-atlantic transport)
VG-60 - The ultimate projected variant powered by a 1,000 hp Hispano-Suiza 12Y-51 supercharged by a two-stage Sidlowsky-Planiol turbo-charger.