The Potez 630 series of twin-engine aircraft was introduced with the French Armee de l'Air (French Air Force) in the late-1930s as an all-modern, metal-clad, heavy-class fighter. Its design kept pace with other twin-engine, multi-role developments witnessed during the period - particularly those emerging from Britain and Germany where their proved a need for heavy fighter types to contend with the growing threat of bombers who saw their own technological growth throughout the decade. Heavy fighters were to offer both performance and armament suitable for successfully engaging larger targets and, when outfitted with bombs, could engage ground targets as needed with equal fervor.
The Potez 630 emerged from a French Air Force requirement of 1934 which called for a multi-role aircraft capable of air control/direction, interception/bomber escorting, and night fighting. Design of the 630 line was attributed to Potez engineers Louis Coroller and Andre Delaruelle and their approach utilized a well-streamlined, metal-skinned body fitting a three-man (seated inline) cockpit at front with a tapering rear section mounting a dual vertical tail fin arrangement. The mainplanes were fitted low along the fuselage sides and ahead of midships with each wing mounting a single radial piston engine along the leading edge. The undercarriage was retractable (save for the tail wheel) and of the "tail-dragger" arrangement which saw two main, single-wheeled legs fitted under each engine nacelle. The long cockpit was covered over in a greenhouse-style canopy with thin framing which offered good views of the surrounding action. The pilot sat at front with a mission specialist at center, and a dedicated gunner at rear. The center crewman position could be eliminated base on mission need and a ventral area allowed for management of lower armament or observation of the passing terrain below. Power was from 2 x Hispano-Suiza 14HBs radials of 580 horsepower each.
As designed, the aircraft showcased a standard armament suite of 1 x fixed, forward-firing 7.5mm MAC 1934 machine gun and 1 x fixed, rear-firing machine gun of same model and caliber in the ventral gondola. The rear gunner managed another of the same gun, though this on trainable mounting hardware in a dorsal position primarily facing aft.
Flight testing of the prototype (Model 63.01) revealed it an overall sound aircraft - first flight recorded on April 25th, 1936. An accident forced a slight tail redesign, producing prototype Model 630.01 and a second prototype, Model 631.01 was used to test Gnome-Rhone 14 Mars engines - first flight of this entry on March 15th, 1937. Without any major modifications following, the line was adopted for formal service by the French Air Force in 1937 through an order numbering eighty aircraft as the "Potez 630". At this same time, the similar "Potez 631" emerged and this variant made use of 2 x Gnome-Rhone 14M radial piston engines which offered better performance and reliability. The French Air Force was equally sold on this design and ordered it through a separate 90-strong contract as "Potez 631 C3". In 1938, yet another order for 50 more aircraft was signed as France geared up for its impending war with hated Germany. Twenty of this batch were also ordered by Finland though France's entry into World War 2 would negate delivery.
Still another form emerged as the "Potez 633" which became a dedicated two-seat light level bomber form. These lost their ventral gondolas and had a standard tandem, two-seat cockpit with the middle crew position taken up by a new internal bomb bay which was to service up to 880lbs of stores. The rear gunner doubled as the bombardier with delivery aided through a periscope. A prototype first flew during the latter part of 1937 and 133 were on order for 1938. However, the design changed some before the end as it was decided against a two-seat design and the third crew added back in for a spread workload. The "Potez 634" became a proposed dual-control trainer and was the Potez 630 fitted with the Gnome-Rhone engines but not furthered. Similarly, the Potez 63.16 T3 was to become a dedicated crew trainer and it only ever existed as a "one-off" prototype.
Dedicated reconnaissance variants became the "Potez 637" and the "Potez 63.11". In the former, the gondola was glazed over and used as the observer's post with the overall designed based largely on the existing 631 model. Sixty modified aircraft matching this form arrived after August 1940. In the latter, the fuselage became deeper and housed a small internal bomb bay or extra fuel while a glazed over nose assembly was used for the observer. 730 of this variant were delivered from September 1939 onwards though 1,365 were originally intended. The 63.11 became the last of the line to enter serial production. These were powered by Gnome-Rhone 14M 4/5 14-cylinder radials of 700 horsepower each.
Deliveries of 630s and 631s began by the end of 1938 and the French Air Force, China, Greece, and Romania all committed to orders for the 633 bombers as well (the French eventually abandoned this pursuit). The Hispano-Suiza-powered aircraft proved troublesome with its performance never satisfactory - therefore quickly given up for the Gnome-Rhone-engined forms. With looming war against its European neighbor, French officials ordered some of the Romanian- and Greek-bound stock to be reconstituted for use by the French Air Force. With war formally greeting Europe in September of 1939 led by the German invasion of Poland, the Potez series was finally placed into combat service some time later - serving in ground attack, night fighting, reconnaissance, and training roles. It fought on into the Battle of France which spanned just a few short weeks from May 1940 into June. Potez 631s were credited with downing 29 German foes.
During the fighting, thought was given to improving the type's armament - and this achieved a considerable upgrade. The forward-facing battery was now made up of three machine guns under the fuselage and four added to the wings, two placed outboard of each engine. The ventral position now fielded three machine guns and two were installed in the dorsal position. The bombload was 440lbs.
The campaign eventually saw the capitulation of France to the German - giving rise to the "Free French" forces with a government in exile and the Axis-aligned Vichy French. Both forces, as well as the Germans and Italians, continued use of available stocks of Potez 630 aircraft while some were passed to Yugoslavia. Free Polish forces also operated the type throughout the war - also through a government in exile following Poland's own surrender the year before.
In practice, the Potez 630 series aircraft were solid contributors though largely limited by their choice of engines which restricted performance when compared to her contemporaries. Elegant aircraft and fully modern, pilots praised the design's sound handling characteristics and combat survivability. Additionally, they were relatively inexpensive to serially produce and could be manufactured in French factories in short order. As heavy fighters however, they proved slow to intercept enemy formations and too slow to tangle directly with lighter fighter types like the Messerschmitt Bf 109 of the German Luftwaffe. Its true value lay in reconnaissance and ground attack work as well as training where the long cockpit served as a proper classroom.
Those Potez 633 model aircraft that managed to be delivered to Greece and Romania saw additional combat service in the years following. Greek mounts operated in the defense of Greece after the Italian invasion of October 1940 and were on the side of the Axis-aligned Romanians when establishing the East Front against the Soviet Union. Some airframes intended for China were reclaimed by the French to be used as local security over Indo-China and were pressed into service during its war with Thailand (1940-1941).
Total production was over 1,100 aircraft and these served into the final days of the war with various parties - mainly given up due to attrition or lack of spares. On the whole, the line could be considered a mixed success that fought the war on both sides.