Potez 63 on the ground
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The Potez 63 was the overall designation for a series of aircraft that between them were the most numerous in French service during the Second World War, acting as night fighters, day fighters, light bombers, reconnaissance aircraft and army co-operation aircraft. Sadly by 1940 the entire family of aircraft was suffering from a general lack of engine power, and was verging on obsolescence, although its impressive manoeuvrability helped reduce losses to enemy action.
On 31 October 1934 the French Air Ministry issued a specification for a twin-engine two or three seat multi-purpose fighter aircraft. The new aircraft would have to fulfil three different roles. It was to be used as a three-seat fighter direction aircraft, used to control the movements of formations of single seat fighters (the C3). It was to serve as a two-seat bomber escort fighter and day attack aircraft (the C2). Finally it was to be used as a two-seat night fighter (the CN2).
The new aircraft was to have a top speed of 280mph at 13,123ft, to be able to climb to that altitude in less than fifteen minutes, to have an endurance of four hours at 199mph, to be armed with two fixed-forward firing 20mm cannon and a flexibly mounted machine gun, and to as manoeuvrable as the single-seat fighters it was expected to operate alongside. The ministry suggested that either 450 Renault inline engines or 600hp Hispano-Suiza or Gnome-Rhone radial engines be used, and the initial weight limits excluded any more powerful (and thus heavier) engines.
Five designs were submitted in response to this specification - the Breguet Br 690, Hanriot H 220, Loire-Nieuport LN-20, Romano 110 and Potez 63. Potez suggested developing two versions of the aircraft - the Potez 630 with Hispano-Suiza engines and the Potez 631 with Gnome & Rhone engines.
The Potez 63 was a low-wing twin-engined monoplane with more than a passing resemblance to the Bf 110. Like the German aircraft it had a twin tail, a streamlined fuselage, and the cockpit was covered by a long greenhouse canopy. The wings were low-mounted. The short central section, between the fuselage and the engine nacelles had parallel leading and trailing edges and no dihedral, while the outer sections had a clear dihedral and straight edges that tapered towards a rounded point. The horizontal surface on the twin tail also had dihedral. The retractable undercarriage folded into the engine nacelles.
The successful manufacturers were asked to build one evaluation aircraft with their own funds. Potez chose to build a prototype of the 630, and work began on the Potez 630-01 in April 1935. The aircraft took almost exactly one year to build, and made its maiden flight on 25 April 1936. At this stage it had a wooden tail with no dihedral. The prototype was slightly damaged in a crash on 6 May, but was soon replaced and sent to Villcoublay for official trials on 3 August. After some early trials the wooden tail was replaced with the production model, and tests resumed in November. The engines were replaced twice, until the prototype was using the Hispano-Suiza 14 Ab 10/11 engines, which provided 640hp at sea level, 700hp at take off and 725hp at altitude. With these engines the fully loaded aircraft reached a top speed of 286mph.
At this stage the Potez company was nationalised, forming part of the National Aircraft Construction Company of the North (SNCAN). The new company was formed on 23 December 1936, and by mid-April had absorbed five aircraft factories, including the Potez plants.
The second prototype, the Potez 631-01, made its maiden flight in March 1937. This aircraft was powered by the Gnome-Rhone 14 Mars radial engine, which provided 570hp at sea level, 700hp at take off and 660hp at altitude. Although the Gnome-Rhone engines were less powerful, they were also smaller, and the Potez 631-01 was only 4mph slower than the 630-01.
Early in 1937 SNCAN received a provisional order for ten evaluation aircraft. This was to be made up of four Potez 630s, three Potez 631s (including the prototype), two Potez 633 B2 light bombers and one Potez 637 A3 reconnaissance aircraft. When this provisional order was confirmed one of the Potez 633s was replaced by a Potez 639 AB2 ground attack aircraft.
In June 1937 SNCAN received a letter of intent for forty Potez 631s (ten two-seat trainers and thirty three-seaters) and eighty Potez 630s, ordered to make up for a shortage of Gnome & Rhone engines. The first of these aircraft were to be delivered in eight months. In December the letter of intent was turned into a formal contract, and fifty Potez 633 B2s were added.
Production of the aircraft actually began in May 1937, before the letter of intent had been issued. The fuselage and tails were built at Caudebec, the wings at Le Havre and the aircraft were assembled at Méaulte, then at Les Mureaux.
Next to be ordered into production was the Potez 637 reconnaissance aircraft, followed by the Potez 63.11 army cooperation aircraft. This version would be built in larger numbers than any other, accounting for three quarters of the total production run. The order for Potez 633s was soon cancelled, and turned into one for Potez 631s. The first production Potez 680 was completed in February 1938, and the type entered service late in 1938.
Combat Record (see individual models for more detail).
Only the Potez 631, Potez 637 and Potez 63.11 saw significant action during the Battle of France. The Potez 630 had been withdrawn because of engine problems and the Potez 633 was mainly used for training.
The Potez 631 saw most use as a night fighter, but the lack of any system for intercepting German raiders (the French didn’t have radar) meant that there were very few combats between the Potez fighter and German aircraft. A small number were used for daylight ground attack missions, but with little success.
The Potez 637 was one of the more modern aircraft in the reconnaissance groups, but losses were heavy. Production of this variant was limited, and the Potez 63.11 played just as important role in these group. The Potez 63.11 was also the most important aircraft in the army co-operation units, where it suffered heavy losses, mostly to ground fire and on the ground (although managed to hold its own against German fighters). By 1940 the entire family was outdated, with the lack of engine power and thus speed being their main weakness, but slow production of the more modern aircraft designed to replace them meant that large numbers of French aircrew were forced to fight in members of the Potez 63 family.
Export Orders
The Potez 63 was made available for export in 1937, and a number of orders were received, although only two were even partly fulfilled. The Potez 633 B2 was the most popular export model. After the French Air Force cancelled its own order for the bomber variant, these export aircraft were the only ones to be constructed, and they served with the Armée de l'Air.
Five countries ordered aircraft from France: China ordered four Potez 631 C3s and five Potez 633 B2s. Greece ordered twenty-four Potez 633 B2s. Romania ordered twenty Potez 633 B2s in a first order and another twenty in 1938. Switzerland ordered one Potez 630 C3 and one Potez 633 B2s. Yugoslavia ordered two Potez 630 C3s and one Potez 631 C3. Finally Avia in Czechoslovakia arranged for licence production of the Potez 636 C3, but production had not got underway when Germany occupied the country.
From these orders Switzerland received its Potez 630. Yugoslavia received one of its Potez 630s, but the other, a dual control trainer, was retained in France.
Variants
The Potez 630 was a fighter version, powered by troublesome Hispano-Suiza engines. It was produced in small numbers but was withdrawn from front line service early in 1940.
The Gnome-Rhone powered Potez 631 was the main fighter version. It was used as a night fighter during the Battle of France, but without radar was unable to intercept many German aircraft.
The Potex 632 was the designation given to one Potez 633 ordered by the Swiss.
Two-seat light bomber with bombs carried internally. French orders cancelled and a small number produced for export.
The Potez 634 was an alternative designation given to the ten two-seat training aircraft ordered in the first production contract.
Fighter version designed for licence production in Czechoslovakia, none built.
Potez 637 A3 reconnaissance aircraft
Reconnaissance version, with observer carried in glazed gondola under fuselage. Produced in significant numbers but being replaced by Potez 63.11 by the spring of 1940.
The Potez 639 AB2 was an attack bomber, one example of which was ordered as part of the ten evaluation aircraft.
Potez 63.11 army co-operation aircraft
The Potez 63.11 was an army co-operation aircraft with a larger fuselage and a glazed nose. It was the most numerous member of the family, and was used by reconnaissance and army co-operation units.
One Potez 631 re-engined to use Pratt & Whitney engines
One Potez 63.11 given a wing with a larger area early in 1940.