PZL P-23
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Bloch MB-210
Potez Po-633B2
Heinkel He-111
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Savoia-Marchetti SM 79B ( JRS-79B )
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The Potez Po-633B2 light bomber / reconnaissance aircraft

In 1934, the French Air Ministry decided to boost the capabilities of the L'Armee de l'air by providing it with a "workhorse" capable of performing all sort of missions. Therefore, they issued a specification for a twin-engine, multi-role plane, to be powered by two small-diameter radial engines conceived and built by Gnome-Rhône and Hispano-Suiza. The plane had to have good armament, to be able to act as a kind of airborne controller for single-seat fighters, to serve as interceptor, heavy fighter and night fighter as well.
A team of engineers from the Potez company, headed by Louis Coroller
and M.Delaruelle, came up with the Potez 63 design. It was a cantilever, low-wing monoplane of basically stressed-skin light alloy construction with an oval-shaped fuselage made up of three sections (semi-monocoque nose and tail sections attached to a four-longeron central section). It had a low-set wing, with a flat constant-chord center section built integrally with the
central part and external panels tapered in thickness and chord. Cockpit was a raised, "glasshouse" type, with sliding panels for easier access. The landing gear was fully retractable, with the main gear retracting rearwards into the undersides of the wing.
First prototype, designated Po-63.01, took off for the first time in April 1936, with a temporary wooden tail, so that it could be easily transformed into the optimal shape. It was powered by two Hispano-Suiza 14Hbs radial engines. After some time, a second prototype, designated as Po-631.01, was completed and started test flights. This plane was powered by two Gnome-Rhone 14Mars engines. After the Po-631.01 was built, the Po-63.01 became the Po-630.01.

 

 
 
After beating its rivals ( the Breguet Bre.690, the Hanriot H.220, Loire - Nieuport LN.20 and Romano R-110 ) in an open contest, the Po-63 managed to make such an impression on the French Air Ministry, that it was quick decided to place an order for a batch of no less than 7 pre-production Po-63 variants.
  The Potez Po-633B2 light bomber  
Eventually, 5 of these versions entered mass-production : - Potez Po-630C.3, a three-seat fighter powered by 2 Hispano-Suiza 14AB-02/03 or -10/11 radial, rated at 650 hp or 700 hp engines and armed with two fixed forward-firing 20 mm cannons plus a rear-firing 7.5 MAC machine gun ( initially was destined for night fighter units, but some planes were sent to single-seat fighter units to act as avions de commandement, meaning command aircraft for single-seat fighters ) ; Potez Po-631C.3, a dedicated three-seat fighter, powered by 2 Gnome-Rhône 14M-4/5 or -6/7 radial, with the same armament ; Potez Po-633B.2, a light bomber, pretty much similar to the 631C.3, but with a glazed lower nose where the bombardier stood , and an internal bomb bay where eight 50 kg bombs positioned vertically could be carried ; Potez Po-637A.3, a three-seat reconnaissance and army co-operation version, fitted with a glazed observation gondola and a Labrely F.20, F.30 or F.50 camera with up to 40 marker flares in the rear furselage, as well as two 50 kg bombs underneath the wings ; Potez Po-63.11A.3, the final army co-operation and reconnaissance version.
The ARR became interested by the Po-633B2 in 1937, and in the spring of 1938 an order for 20 modified planes was placed. Changes consisted in fitting electrically operated Ratier propellers, inertia engine starters, and provision for a Labrely F.30 or F.50 reconnaissance camera in the weapons bay. Defensive armament was changed as well : 3 Browning FN 7.92 mm machine guns were mounted, one fixed forward-firing, one
rearward-firing in the rear cockpit and one rearward-firing in a new ventral hatch position. In 1939, all 20 Po-633B2's arrived in Romania, where they were assigned to the 74th and 75th Bomber Squadrons of the 2nd Bomber Group. Afterwards, 20 more airplanes were ordered but it seems that only 1 was delivered, as the rest were embargoed by the French, and pressed into service with their own air force.
At the start of operation Barbarossa, 17 Po-633B2 were standing by ready for action. They did a pretty good job, but took heavy losses from AA fire, so after just one month the 75th Bomber Squadron handed in all its remaining planes to the 74th Squadron. After participating in the siege of Odessa, the 74th had been reduced to 5 operational Po-633B2's. In late 1941, 9 more Po-633's were received from Vichy France in exchange for various oil products. Most were assigned to the 74th Bomber Squadron ( they had 9 Po-633's when they were sent to the east front ) but it seems that some were given to the 3rd Long Range Recon Squadron as well. Both units took part in the Stalingrad campaign, but were pulled out of action and sent home by early 1943. Afterwards, surviving aircraft were used as trainers for night fighter pilots. Generally, the Po-633's achieved a good combat reputation, mainly for its good handling and good survivability, being able to take considerable damage and still make it back home.

Technical data of the Potez Po-633B2

Wingspan
16 meters
Length
11.07 meters
Height
3.62 meters
Weight (empty)
2450 kg
Weight (loaded)
3760 kg
Maximum speed at 6000 meters
438 km/h
Maximum operational ceiling
9000 m
Range
1300 km
Engine
Two Gnome-Rhone GR 14Mars rated at 660 HP
Armament
Three 7.92 mm FN machine guns
Payload
Up to 400 kg of bombs ( 8x50 kg )
Crew
3
Numbers received
30

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