Bloch MB 151, 152
Type MB 151 C1 Single seat fighter MB 152 C1 Single seat fighter
Engine 1 Gnome-Rhône 14N-35 1 Gnome-Rhône 14N-25 with a Gnome-Rhône 2590 propeller
Dimensions Length 9,104 m, height , span 10,570 m, wing area 17,50 m2 Length 9,104 m, height , span 10,570 m, wing area 17,50 m2
Weights Empty 2073 kg, normal flying weight 2522 kg, max. flying weight 2800 kg Empty 2103 kg, normal flying weight 2691 kg, max. flying weight 2800 kg
Performance Max.speed 470 km/h at 4550 m, climb to 4000 m 7 min. ., service ceiling 10080 m Max.speed 482 km/h at 5500 m, climb to 4000 m 6 min. 8 sec., service ceiling 10300 m, range at 5500 m 580 km
Armament   2  7,5 mm machine-guns MAC 34   in the wings
2  20mm cannons Hispano Suiza HS-404 in the wings
On 13 July 1934, the Service Technique Aéronautique (Aeronautical Technical Service) of the French Air Force issued the "C1 design" requirement for a new and completely modern single-seat interceptor fighter. Envisioned to make use of a monoplane layout and a retractable undercarriage, the prospective fighter aircraft was to serve as a replacement for the French Air Force's existing inventory of Dewoitine D.371, Dewoitine D.500, and Loire 46 aircraft. Amongst the various aviation companies who took interest in the specification, to which the potential for a large production order was attached, was French aircraft manufacturer Société des Avions Marcel Bloch.
The design team, headed by Maurice Roussel, was assembled at Bloch's Courbevoie facility in Paris. They designed an all-metal stressed skin monoplane, powered by a single 930 hp Gnome-Rhône 14Kfs radial engine and armed with a pair of wing-mounted Hispano-Suiza-built HS.404 cannon. During September 1935, construction of the type's first prototype, designated as the Bloch 150-01, commenced.
Although the C.1 competition was ultimately won by a rival design, the Morane-Saulnier M.S.406, it was decided to independently continue with the design's development. During 1936, these efforts culminated in the first attempted flight of the MB.150.01 prototype; unfortunately, the aircraft proved unable to leave the ground during the attempt. Disappointed, work on the design was temporarily halted, but development was resumed during early 1937. Following the implementation of various modifications, consisting of a strengthened wing of greater area, revised undercarriage arrangement and the installation of a  940 hp Gnome-Rhone 14N-0 radial engine with a three-blade constant speed propeller, on 29 September 1937, the MB.150 finally conducted its maiden flight.
Months later, the MB.150.01 was handed over to the Centre d'Essais du Materiel Aerien (CEMA) for service trials; during one such official test flight in December 1937, a maximum recorded speed of 434 km/h was attained. As a result of the CEMA flights, the prototype's performance proved to be sufficiently interesting as to warrant further development. This brought, at the beginning of 1938, a small increase in the aircraft's wing span, the replacement of the twin wing-mounted radiators by a single unit installed between the wheel wells, and the installation of an improved 14N-7 engine, which led to the prototype being re-designated as the MB.150.01M (M standing for modified). During spring 1938, further trials of the modified aircraft were performed by CEMA.
By this point, wider circumstances within France, such as the declining diplomatic situation between the European powers and the enactment of several urgent re-equipment programmes for the French Air Force, proved favourable for the MB.150. Specifically, on 15 March 1938, one such programme, referred to as Plan V, was adopted, calling for the near-unrealistic delivery of 940 modern fighter aircraft to the Air Force within the space of a year. Even the most optimistic projections saw 285 M.S.406 fighters delivered; while the MB.150 was deemed to have not yet completed development, it was decided to include the type within the production.
Accordingly, on 7 April 1938, upon the completion of trials in late spring 1938, the newly formed manufacturing consortium SNCASO received an initial order for a pre-production batch of 25 aircraft which, upon successful completion of the MB.150's development programme, was followed by the confirmation of a sizable order for 450 aircraft. Initially, 300 aircraft were to be delivered to the French Air Force by 1 April 1939; this was later cut down to 206 aircraft. In reality, only a single aircraft had been delivered by the prescribed deadline; other aircraft types also proved similarly unable to attain the tight delivery dates.
However, there was no direct production of the MB-150.01 as the aircraft having been deemed to be unsuitable for mass production. Amongst other changes needed, the structure of the airframe had to be redesigned in order to suit mass production. During early April 1938, an order was received for a three further prototypes; these were to explore the possibilities for installing more powerful engines of both French and American origins, such as the Hispano-Suiza 14AA, Pratt & Whitney R-1830 Twin Wasp, and further derivatives of the Gnome-Rhône 14N engine. Accordingly, this design effort led to the production of the MB.151.01 and MB.152.01 prototypes, which were developed and produced in parallel.
The first pre-production prototype, the MB.151.01, was quickly assembled at Courbevoie using the new simplified construction methods developed. This aircraft, which was fully armed, performed its first flight at Villacoublay Airfield, Île-de-France, on 18 August 1938. According to Christesco, the performance of the MB.151.01 was initially disappointing leading to efforts to rectify performance issues. Development, and thus mass production, was delayed by two separate issues, the overheating of the engine (resulting in multiple oil coolers being trialled and the most efficient of these adopted) and the aircraft being poorly balanced on its pitch axis at high speeds. Additionally, neither the prototype nor the production MB.151 were able to attain 480 km/h, the design's estimated maximum speed.
According to Christesco, the MB.152.01 was "the first true aircraft" of the series. This model was equipped with a more powerful 1,030 hp Gnome-Rhône 14N-21 engine, capable of an elevated top speed of 520 km/h, and equipped with a revised armament arrangement. On 15 December 1938, the MB.152.01 prototype performed its maiden flight. During January 1939, it was refitted with a more production-representative 1,000 hp Gnome-Rhône 14N-25 engine; various alternative engine cowlings and propellers were also trialled for the purpose of addressing an engine cooling problem. In order to prevent further delays to the production aircraft, a large cowling was adopted, which produced elevated drag levels and in turn negatively impacted on the MB.152's flight performance.
The manufacturing of the fighter was divided amongst the various branches comprising SNCASO. Aside from a handful that were assembled at Courbevoie early on, roughly half of all aircraft produced were manufactured at Chateauroux, Berry while the other half were built at Bordeaux-Merignac, Nouvelle-Aquitaine. From January 1940 onwards, production was centered at Chateauroux alone. During December 1938, the first of the pre-production aircraft were completed; on 7 March 1939, the first production fighter was delivered to the French Air Force. By mid-May 1939, only 22 aircraft, a combination of MB.151s and MB.152s, had been dispatched; of these, only 10 had been accepted by the Air Force.

Upon evaluation, early deliveries were deemed unsuitable for combat operations, principally due to issues with the tailplane; thus, plans were laid for the first 157 production fighters to be stored awaiting modification, while additional production examples were built with the correction made. Furthermore, the type was initially confined to performing training duties alone; prior to the outbreak of the Second World War, only a single squadron, allocated to the 1st Escadre de Chasse, received the type. Upon the eve of the conflict, around 249 aircraft had been manufactured; of these, roughly 123 aircraft had been accepted by the Armée de l'Air. However, few of these were considered to be flyable, the majority missing their gunsights and propellers.
On 26 September 1939, the first modified MB.152s were delivered to the French Air Force; the first of these fighters were allocated to active squadrons by early October and, by mid-November 1939, two separate Groupes de Chasse (fighter groups) had been equipped with 26 MB.152s each. At this point, the type still demonstrated some unfavourable flight characteristics, such as during steep dives. Meanwhile, increasing numbers of MB.151 aircraft were being delivered to be squadrons for training purposes in advance of their anticipated conversion to the MB.152.[12] During the initial stage of the conflict, known as the Phoney War, very few engagements between the MB.152 and the aircraft of the Luftwaffe occurred; in this period, only a single kill of a Junkers Ju 88 was recorded.
During the Battle of France, a mixture of MB.151s and MB.152s equipped nine Groupes de Chasse; the MB.152 held the distinction of being the most numerous aircraft remaining in service during the final weeks prior to the signing of the Armistice of 22 June 1940. While they were considered to be outmatched by the faster Messerschmitt Bf 109E, the pilots of Bloch MB.152s destroyed at least 188 enemy aircraft, for the loss of about 86 Blochs. They proved to be tough aircraft, able to withstand considerable battle damage, rapidly reach high speeds during a dive, and functioned well as a gunnery platform.]
However, in comparison with its other French contemporaries, according to aviation author Michel Cristesco: "the MB.152 was the least successful in combat and the one that suffered the heaviest losses". The type suffered some numerous issues and shortcomings; these problems included poor agility, unreliable guns, a relatively low range 600 km  compared to 660 km for the Bf 109E) and being considerably underpowered. Writing of its faults, Cristesco attributed two major points for its short performance; its inadequate manoeuvrability and its range.
Following the Armistice, a total of six groups continued to fly in the Vichy French Air Force until this was disbanded on 1 December 1942, the aircraft being passed over to the Royal Romanian Air Force by the Germans. By April 1941, the German Armistice Commission had agreed with a proposal to standardise the Vichy Air Force onto the Dewoitine D.520, resulting in all other single-engine fighters being phased out. The Germans seized around 173 fighters, 83 of which being reportedly serviceable, which were impressed into service with the Luftwaffe. Chrisesco alleged that around 95 MB.152s were secretly modified during late 1941/early 1942 with a rear-fuselage fuel tank, giving them the range to cross the Mediterranean Sea to freedom.
Though the Greek government had ordered 25 MB.151s, actually only nine of these were actually exported to Greece by the time of the Armistice being signed. Those that were delivered were still in the process of working up when the Greco-Italian War broke out, leading to the wider Balkan Campaign between the major European fighters. The MB.151 fighters flew with the 24th Moira Dioxis (Fighter Squadron) of the Hellenic Royal Air Force, stationed at Elefsina against the Italians and Germans, scoring several air-to-air victories until 19 April 1941, when the last of Greece's MB.151s was shot down.
At one stage, the Bulgarian government was in the process of negotiating the acquisition of MB.152 fighters with the Vichy government. During February 1943, a contract for delivery of 20 aircraft was signed, but this was vetoed by the German authorities, which by now had a controlling say within Vichy French politics. Instead, Bulgaria later received a series of Dewoitine D.520s to meet their needs.
During 1944, several surviving MB.152s were liberated at an airfield in mid-southern France. After being flight-tested and evaluated, and painting out the Balkenkreuze, and swastikas, they were fitted with more-powerful American engines and went up against the last remnants of the Luftwaffe with the Free French.
Total production :
136 Bloch MB 151 with Gnome Rhône 14N35 engine: 25 for Greece, 30 for naval aviation, 85 for schools and 4 for SNCASO for testing
555 Bloch MB 152 broken down as follows :
203 aircraft with Engine Gnôme-Rhône 14N25 or 14N39 (Serial nr from 9 to 300)
352 aircraft with Engine Gnôme-Rhône 14N49 (nr 301 to 431, nr 497 to 500 and nr 501 to 696 )
The Germans seized around 173 fighters, 83 of which being reportedly serviceable, which were impressed into service with the Luftwaffe.