Potez 63 / 630 / 631 / 637
The Potez 63 was built originally to a 1934 French Air Ministry programme calling for a 'Multiplace legere de Defense', literally a light multi-seat defensive aircraft. In practice the specification called for an aircraft to perform the three roles of fighter control (three-seat C3); daylight interception (two-seat C2); and night-fighter (two-seat Cn2). The Potez 630 was a twin engine, monoplane, fully metallic three-seater with efficient aerodynamic lines and twin tailplanes. The long glasshouse hosted the pilot, an observer or commander who was only aboard if the mission required it, and a rear gunner who manned a single flexible light machine gun.
The Potez 63.01first prototype flew on 25 April 1936. It was an all-metal stressed-skin cantilever monoplane with two 432-kW (1580-hp) Hispano-Suiza 14AB10/11 radials, and a retractable landing gear.
French re-equipment policies were blurred by lack of purpose (being confused by the likely form of warfare being studied by Germany), with the result that orders for development aircraft included four-general purpose two/three-seat day/night fighters, three two-seat night-fighters, one light bomber, one reconnaissance aircraft and one close-support aircraft.
Ten further prototypes were tested (including use of the Gnome-Rhone 14 radial) before production orders were placed in 1937 for 80 Potez 630s (two 432kW Hispano-Suiza 14 radials) and 80 Potez 631 C3 fighters (Gnome-Rhone 14 Mars radials). The production in three main streams was started by the nationalised SCAN organisation.
Fifty additional Potez 631s were ordered in 1938 of which 20 were diverted to Finland (these aircraft did not arrive in Finland). A typical feature of the 630 and 631 was the frontal armament, which originally consisted of two 20 mm Hispano-Suiza HS.404 cannons in gondolas under the fuselage, though sometimes one of the cannons was replaced by a MAC 1934. Later in their career, 631s received four similar light machine guns in gondolas under the outer wings, though it was theoretically possible to fit six.
The heavy fighter stream included the Potez 630 (82 with Hispano-Suiza engines) and Potez 631 (202 with Gnome-Rhone engines). The light bomber stream included the Potez 633 (71 mostly for export but mainly retained by France) and Potez 637 (60 for reconnaissance). The tactical reconnaissance and army co-operation stream included the Potez 63.11 (925 aircraft) and a number of experimental fighters and dive-bombers.
Dissatisfied with its strategic reconnaissance aircraft such as the troublesome Bloch MB.131, the Armée de l'Air ordered the development of a derivative of the Potez 631 heavy fighter for this role. The observer was to be housed in a gondola under the fuselage. While particularly uncomfortable, this arrangement resulted in a Potez 637 that retained most of the qualities of the 631. 60 examples were ordered in August 1938 and delivered. Unlike many contemporary French aircraft, production of the Potez aircraft was reasonably prompt and the first deliveries were effected before the end of 1938. The 63 had been designed with mass production in mind and as a result, one Potez 630 was cheaper and faster to manufacture than one Morane-Saulnier M.S.406. As production tempo increased, a number of derivatives and experimental models were also developed and produced with exceptional rapidity.
The Potez 633 B2 was a light bomber version with a partially glazed nose, 40 of which were ordered by Romania and others by Greece. In the event only 21 of the Romanian aircraft were delivered, the rest retained by France. The Potez 637 A3 was a three-seat reconnaissance version with a ventral gondola for the observer, 60 of which were built.
The Armée de l'Air was desperate to re-equip its army cooperation units which had particularly antiquated equipment, but since the development of the Potez 637, had completely changed its mind about how the observer position should be arranged. Potez was therefore required to develop a variant that, while retaining the wings, engines and tail surfaces of the 631, hosted the observer in a more conventional nose glasshouse. Because the pilot needed to be seated above the observer, the Potez 63.11's fuselage was taller, which resulted in top speed degradation and reduced manoeuvrability. As a result the final production version, the Potez 63.11 proved very vulnerable, despite being protected with some armour and a basic self-sealing coating over the fuel tanks.
As a secondary light bomber capability was part of the requirements (though it was rarely if ever used), the fuselage accommodated a tiny bomb bay, carrying up to eight 10kg-class bombs. This bomb bay was replaced by an additional fuel tank on late examples. Additionally, two 50kg-class bombs could be carried on hardpoints under the inner wings. Frontal armament was originally one, then three MAC 1934s under the nose, and many 63.11s were equipped with additional MAC 1934 guns in wing gondolas as the 631s. The first Potez 63.11 No.1 and second No.2 prototypes first flew in December 1938, and no less than 1,365 examples were on order in September 1939, of which 730 were delivered.
Potez 63-11s were delivered from November 1939 and served with 40 GAO (observation Groupes) and 13 reconnaissance Groupes by May 1940.
Although a night-fighter prototype had flown in March 1937 as the Potez 631-0, relatively little importance was placed on the Potez 631 night-fighter, and it was not until June 1938 that production orders totalling 207 were confirmed.
The Ilmavoimat / Maavoimat evaluation team looked at a number of diferent variants of the Potez 630 in early 1938. There report indicated that all members of the family (possibly except the Potez 63.11) shared pleasant flying characteristics. They were well designed for easy maintenance and could be fitted with a heavy armament for the time (up to 12 light machine guns for the Potez 63.11 design that was being worked on). Although not heavily built they seemed capable of absorbing considerable battle damage. Unfortunately the Potez 63 family, like many French aircraft of the time, simply did not have sufficiently powerful engines to endow them with an adequate performance. However, while the aircraft was considered reasonably good, it by no stretch met the STOL Observation / Medical Evac requirements of the aircraft that was being looked for.
By 1 April 1939 the Armee de l'Air had taken delivery of 88 aircraft, of which 20 were in service; in May two night-fighter units, Groupes de Chasse de Nuit GCN III/l and II/4, and one day fighter unit, GC II/8, were equipped with about 30 aircraft; four other Potez 631s were serving at Djibouti. At the outbreak of war a total of 206 aircraft had been delivered, and the type had also joined GCN 1/13 and GCN 11/13, as well as seven escadres de chasse. Some aircraft were later transferred to the Aeronavale. When the German attack opened in the West the various Potez 631 units were in constant action both by day and night, although lack of radar prevented much success during the hours of darkness. In the first 11 days of the campaign Aeronavale's Flotille F 1C shot down 12 German aircraft for the loss of eight, but the Armee de l'Air night-fighter units were ordered to assume day ground-attack duties, losing heavily to enemy flak. Moreover, losses were exceptionally heavy to Allied guns and fighters as a result of the Potez 631's superficial similarity to the German Messerschmitt Bf 110; it has been estimated that as many as 30 of the French aircraft were shot down in error. In all, Potez 631 night-fighters destroyed a total of 29 German aircraft in the Battle of France, but for a loss of 93 of their own number. Of the remainder about 110 were in the Free French Zone (Vichy France) at the time of the armistice, but their number dwindled quickly because of a chronic lack of spares, although ECN 3/13 moved to Tunisia with a small number of Potez 631s in June 1941.
Armament comprised two forward-firing and one rear-mounted 7.7mm machine-guns. Potez 637s equipped five reconnaissance Groupes and during the battle for France suffered heavy losses.
After the outbreak of the Winter War, 20 Potez 631s were ordered diverted to Finland. These aircraft arrived in mid-April 1940, having been flown to the UK where they were picked up by Ilmavoimat Ferry Pilots and flown via Norway and Sweden to Finland. In Ilmavoimat service, they were found to be underpowered and slower than many of the Soviet bombers, as well as undergunned. A rush project was undertaken to replace the engines with the Finnish-built and more powerful Hispano-Suiza 12Y’s, and every one of the aircraft was fitted with two nose-mounted 20mm cannon and four machine guns under the wings. In addition, the internal bomb bay was replaced with an additional fuel tank to extend the range.
Ilmavoimat Potez 631’s undergoing modifications at the Veljekset Karhumäki factory at Tampere, May 1940.
The aircraft finally entered service in August 1940, by which time the war was almost over. The Ilmavoimat went on to use them in the night-fighter role that the French had intended them for. They were not particularly successful in this role and were retired from active service and used as trainers from 1941.
A total of 748 examples were built.
John Garric recreated an example of the long extinct Potez 63-11 twin-engined reconnaissance aircraft.
Potez 637 A no (C591 de la lère Esc. Du G..II/3 January 1940
Engines: two Gnome-Rhône 14M
Maximum speed: 264 mph
Range: 932 miles
Service ceiling: 27,885 ft
Armament: 1x fixed, forward-firing 7.5 mm MAC 1934 machine gun, 1x fixed, rearward-firing 7.5 mm MAC 1934 machine gun, 1x flexible, rearward-firing 7.5 mm MAC 1934 machine gun
Bombload: 4x 50 kg (110 lb)