French twin-engined heavy fighter of World War II
The Potez 630 and its derivatives were a family of twin-engined, multirole aircraft developed for the French Air Force in the late 1930s. The design was a contemporary of the British Bristol Blenheim (which was larger and designed purely as a bomber) and the German Messerschmitt Bf 110 (which was designed purely as a fighter).
The Potez 630 was in use by several operators during the Second World War. Following the Battle of France, both the Vichy French Air Force and Free French Air Forces used the type; a number of captured aircraft were operated by several air wings of the Axis powers. After the end of the conflict in 1945, a handful of aircraft were used for training purposes for some time.
Development.
Origins.
On 31 October 1934, the French Ministry of Air issued a specification for a heavy fighter. The specification demanded the aircraft be capable of performing three principal roles: fighter direction, in which it was required to lead formations of single-engine fighters with sufficient maneuverability; day attack, in which the type was also to escort friendly close air support and bomber aircraft; and nightfighter operations. Specified performance details included a maximum speed of 450 km/h at 4,000 meters, a 300 km/h cruising speed, and an endurance of at least four hours. Armament requirements included two fixed forward-firing 20 mm cannons and a single machine gun to the rear for self-defence. The sought aircraft was also required to accommodate two/three seats along with a twin-engine configuration; however, some of the performance limitations imposed upon the aircraft, such as the maximum weight, served to restrict the range of suitable engines to power the type.
The original "Potez 630" was developed to meet this specification; two variants of the aircraft were originally submitted for consideration, one (the 630) powered by Hispano-Suiza 14AB radial engines and the other (the 631) with the Gnome-Rhône 14N. Other companies also produced submissions in response, including Breguet Aviation, Hanriot, Chantiers aéronavals Étienne Romano, and Loire-Nieuport. Each of the competing manufacturers were requested to produce a single prototype for evaluation at their own expense; work on the first prototype, designated as the "Potez 630-01", commenced in April 1935. In addition to the Potez 630, the same specification had ultimately resulted in the successful Breguet 690 series of attack aircraft.
On 25 April 1936, the Potez 630–01, equipped with a pair of 580 hp Hispano-Suiza 14, conducted its maiden flight from Méaulte, Picardy. Initially, the prototype was equipped with an experimental feature in the form of a braced horizontal stabilizer that incorporated no dihedral. On 6 May 1936, the prototype suffered some damage due to a hard landing following the mid-air loss of a propeller blade. On 3 August 1936, after receiving repairs, the Potez 630-01 was transferred to Villacoublay Air Base, Île-de-France; it was soon refitted with an alternative tail arrangement similar to later production aircraft and long-stroke landing gear. On 20 November 1936, flight testing of the prototype resumed; it was shortly thereafter delivered to the "Centre d'Essais de Matériels Aériens" (CEMA) for official tests.
The original engines of the Potez 630-01 were progressively replaced with improved models of Hispano-Suiza engine, gradually increasing power to reach 700 hp on takeoff. At its maximum takeoff weight of 3,850 kg, the prototype was capable of a maximum speed of 460 km/h and a maximum range of 1,300 km when flown at an economical cruising speed of 300 km/h. In March 1937, the second prototype, designated Potez 630–02, performed its maiden flight from Méaulte. The Potez 631-01 was damaged after a landing with its landing gear not being locked into the down position; after repairs, it was handed over to CEMA for official trials in November 1937.
Production.
On 23 December 1936, the Société nationale des constructions aéronautiques du Nord (SNCAN) was officially formed, grouping together five French aircraft factories; further amalgamations into SNCAN soon took place, including Potez in early 1937. Shortly following its establishment, SNCAN received a provisional order letter for ten experimental aircraft; four of these were derived from the Potez 630, three from the Potez 631 (one being the existing 631-01 prototype), two Potez 633 light bombers and one Potez 637 aerial reconnaissance aircraft. This was promptly confirmed by a contract, under which one Potez 633 was replaced by a single Potez 637 low level ground attack aircraft.
In June 1937, an order for an initial production batch of 10 two-seat and 30 three-seat Potez 631 day fighters was received, the first five of which were to be delivered by February 1938. As large-scale manufacturing of the Gnome-Rhône 14M engines had yet to be achieved and thus was not able to reach the desired production rate of the Potez 630, an additional order was placed for 80 aircraft powered by the alternative Hispano-Suiza engine. The first 48 aircraft to be produced were equipped with Hispano-Suiza 14AB02/03 engines, these were succeeded on later models by the improved Hispano-Suiza 14AB10/11. In December 1937, regular contracts took the place of the provisional letters; a further order for 50 Potez 633 light bombers was also received, bringing the total orders for the type to 180, including the ten prototypes that had been ordered.
During the late 1930s, the Potez 630 received considerable foreign interest; in addition to France, many countries were in the process of re-equipping their air forces. One such foreign venture was the acquisition of a licence to manufacture by the Czechoslovakian aircraft firm Avia to produce a variant of the aircraft, designated as the "Potez 636"; none were completed prior to Czechoslovakia's annexation by Nazi Germany in 1938. In 1938, a further 50 additional Potez 631s were ordered, of which 20 were to be diverted to Finland, although they never reached that country. A number of firm foreign orders was placed with SNCAN for the type; the Republic of China ordered four Potez 631 and five Potez 633, the Kingdom of Yugoslavia ordered two Potez 630 and one Potez 631, the Kingdom of Romania ordered 20 Potez 633, the Kingdom of Greece ordered 24 Potez 633, and Switzerland ordered one Potez 630 and one Potez 633.
In May 1937, series production of the Potez 630 commenced. Manufacturing work on the aircraft's various sections and components was shared out across various SNCAN facilities; the fuselage and tailplanes were produced in Caudebec-en-Caux, Normandy, the wings were made at Le Havre, Normandy, and final assembly was initially performed at Méaulte; the assembly work was later transferred to Les Mureaux. In February 1938, the first production Potez 630 conducted its maiden flight; on 23 February, the French Air Force accepted their first production 630 aircraft. Early on, production of the Potez 630 was hit by considerable delays, caused by a shortage of engines, propellers, and cannons; the first batch of Potez 630s were armed with four machine guns instead of the two 20 mm Hispano-Suiza cannons. On 2 August 1938, the first Potez 631 was officially accepted.
On 15 March 1938, a major re-equipment and expansion program of the French Air Force, known as "Plan V", was approved. While there had been intentions to order a more capable twin-engine aircraft, these were not ready for production, thus the Potez 631 and 633 were retained for this production program, which first involved 207 twin-engined day-and-night fighters along with 449 daytime light bombers. On 25 March 1938, the order for the Potez 633 was increased to 125 bombers, which were also requested to be three-seaters. The Potez 633 orders were subsequently cancelled, ordering additional Potez 631 aircraft in their place; further orders of the Potez 631 were placed to allow for the speedy withdrawal of the troublesome Potez 630. Between January and June 1940, an average production rate of 100 aircraft per month was maintained.
Design.
The Potez 630 was a twin engine, monoplane, fully metallic three-seater with efficient aerodynamic lines and twin tailfins. The basic design allowed for the type to replace various obsolete aircraft in the French Air Force in a wide range of roles. The long glasshouse housed a crew of three, comprising a pilot, an observer or commander who was carried based upon mission requirements, and a rear gunner who manned a single flexible light machine gun. The Potez 637 featured a glazed gondola located beneath the fuselage for an observer to be carried in the prone position. Some variants, such as the Potez 631 and 633, had a vertical bomb bay located between the two crew members. The 630 was a relatively simple and sound design, requiring an average of 7,500 man-hours to assemble each aircraft. All members of the family (with the possible exception of the Potez 63.11) shared pleasant flying characteristics and were designed to allow for easy maintenance.
As a day fighter aircraft, the performance of the Potez 631 C3 was relatively disappointing, due to a low maximum speed and inadequate rate of climb compared with contemporary fighter aircraft. As a night fighter, lack of detection equipment drastically limited their effectiveness. Later models had a heavy armament (12 machine guns for the Potez 63.11). The Potez 63 family, as with the contemporary Fairey Battle and Bristol Blenheim bombers and like many French aircraft of the time, proved vulnerable to Messerschmitt Bf 109s. Their similarity to the Messerschmitt Bf 110, both being equipped with twin engines, twin fins and a long greenhouse canopy, is believed to have resulted in several aircraft being lost to "friendly fire".
Operational service.
Introduction.
From May 1938, production Potez 630 fighters started to be delivered; the first improved Potez 631 aircraft were received in August that year. Potez 630 and 631s, in two-seater configuration, were soon used to replace obsolete ANF Les Mureaux 113 used as night fighters, while single-seat fighter groups received a number of three seat Potez 63s to act as command aircraft, from which formations of single-seat fighters would be directed and co-ordinated by radio. In July 1938, the first fifteen Potez 630 aircraft participated in the Villacoublay Air Show.
In May 1938, the "Armée de l'Air" (French Air Force) placed an order for 125 Potez 633 light bombers; additional orders had also being placed by Romania and Greece for 20 and 24 Potez 633s respectively. France cancelled its order for Potez 633s in the summer of 1938, but further orders for the 633 were placed by Romania (for 20 more aircraft, which had been part built under the French order), and from China, for nine. Deliveries to Romania started late in 1938, with the Greeks receiving their first aircraft in the spring of 1939. In August 1939, with the risk of war increasing the French government requisitioned 32 Potez 633s from the Greek and Romanian orders that were still in France awaiting delivery.
By September 1938, the Potez 630 had begun to supplant the obsolete Bloch MB.200 bomber in the fighter direction role; however, the Potez 630's engines proved so troublesome in service that most units were rapidly re-equipped with the Potez 631 prior to the outbreak of the Second World War. By 1 April 1939, a total of 77 Potez 630 and 88 Potez 631 aircraft had been accepted by the French Air Force. The retirement of other obsolete French aircraft, such as the Morane-Saulnier M.S.225 and Dewoitine D.510, could be accommodated for by the increasing numbers of Potez 631s. Just prior to the outbreak of the Second World War, the French Air Force had 85 Potez 630s, 206 Potez 631s, 22 Potez 633s, 63 Potez 633s, and 5 Potez 63.11 aircraft.
The Potez 633 aircraft that were exported to Greece and Romania saw greater service than their French counterparts despite their limited numbers. Greece had nine Potez 633s in service when Italy invaded Greece in October 1940. These were used for bombing attacks against Italian supply lines until shortage of spares forced their withdrawal. In June 1941, Romania joined Germany in the invasion of the Soviet Union. Two squadrons were equipped with the Potez 633 which were used to support the Romanian army as it advanced towards Odessa. In 1942, they were replaced by Junkers Ju 88 bombers, allowing the survivors to be transferred to the advanced training role.
Second World War.
On 28 August 1939, the French Air Force initiated the mobilisation of its units, including those equipped with the Potez 630 series. Due to requests from French Naval Aviation some Potez 631 aircraft were soon diverted to replace their Dewoitine D.371 fighters. In February 1940,