Bloch carried out work on an all-metal monoplane with retractable landing gear and two-row radial engine solely at its own expense, on an initiative basis. The design bureau was headed by engineer Maurice Roussel. Prototype fighter designated MB. 150, was built at the firm's Courbevoie plant in mid-1936.

The prototype "Bloch" 150-01, which marked the beginning of the production of single-seat French fighters, could hardly boast of a successful start to its "career" - twice, in June and in August, it could not get off the ground during test flights. After significant modifications and replacement of the engine with a more powerful Gnome-Rone, the flight took place on September 29, 1937. The purpose of the ensuing changes was to prepare the aircraft for production. It was ordered as "Bloch" -151. However, instead of more than two hundred fighters intended for the French Air Force, on April 1, 1939, only one was delivered. Poor flight performance, coupled with engine overheating and poor performance of control devices, led the aircraft, after some alterations, to retraining into a training machine. Only 140 aircraft were built. In April 1938, a contract was signed for three more models, which appeared under the numbers 152, 153, 154. Only 152 reached the stage of industrial production. "Bloch" 152-01, significantly different from its predecessor, had a "Gnome-Rhone" engine and first took off on December 15, 1938. The SNCA du Sud Ouest factories were engaged in the production of this aircraft, which by that time had absorbed the company of Marcel Bloch.

The first orders for "Bloch" 152 came for 288 aircraft, but by the beginning of the war only one squadron was completed, and its aircraft were not ready for combat. By January 1940, the French Air Force had over a hundred Bloch 152s that could fly, and twice as many that could not fly as they did not have propellers. In total, 482 aircraft entered service, but by the end of July 1940, only two thirds of them remained. Many of the surviving aircraft were used by the Vichy government's air force, 20 were transferred by the Germans to Romania. At almost the same time, the Royal Greek Air Force received 9 Bloch 152 aircraft from France (out of 25 ordered).

The SNCASO company did not limit itself to the release of MB only. 152, and shortly before the start of the war, the design bureau of Marcel Bloch developed several more variants of the Bloch fighter. Among them were aircraft equipped with American power plants. Since October 1938, work was underway on the MB. 153 with Pratt-Whitney R-1830-SC3G Twin Wasp motor. Prototype MB. 153-01 made its first flight in April 1939, then was tested at SEMA and was returned for design improvements. After repeated tests, he was accepted by representatives of the Air Force and then flew in the south of France. Fighter MB. 154 was planned to be equipped with the Wright R-1820-G205A engine, but this motor entered the country when there was no need for it.

The engineers achieved the best result by simply improving the Bloch MB.152 with the Gnome-Ron 14N49 engine and the Xavier 371 propeller. Thus MB was born. 155, developed under the guidance of leading designers of the firm SNCASO G. Fando and L. Servanti. MB prototype. 155, which first took off on December 3, 1939 in Deola, was a simple alteration of the serial MV.152, on which a smooth hood of a larger diameter was mounted, the oil cooler was moved from under the left wing to the carburetor air intake fairing, and the horizontal tail struts were eliminated. To improve the aerodynamic shape of the fuselage, overhead rounded bulwarks were installed between the firewall and the seventh frame. A little later, the ailerons of the aircraft were equipped with trimmers, and the Xavier propeller was replaced by the Bloch propeller. Due to the insufficient strength of the tail unit, the stabilizer struts had to be reinstalled.

Prototype MB. 155 was tested until the spring of 1940 and generally showed satisfactory flight characteristics. Compared to the MV.152, it had slightly better maneuverability and surpassed its predecessor in maximum speed by 25 km / h.

Serial production of the new Bloch was planned to be deployed in Deola, where the final assembly of aircraft from units supplied by subcontractors took place.

The first serial MB. 155 was flown on April 3, 1940 and differed from the prototype by slightly extended, rounded sides of the fuselage, which made it possible to increase the fuel tank capacity from 427 to 480 liters. The canopy of the cockpit also acquired a rounded shape, and inside it was supposed to place a flat armored glass "triplex".

The armament remained the same: two 20mm cannons and two 7.5mm machine guns with drum-type magazines. Until mid-June, three MBs rolled off the assembly lines. 155, and by the end of the war the rate of production had increased to three aircraft a day.

The serial production of fighters stopped only when the German troops were already close. On June 18, two MV.155s were killed by enemy bombs at the airfield, and the remaining aircraft were evacuated to the south of France.

Photo	Description
	Drawing MB.152 C1
	Prototype Bloch MB150-1M

Bibliography

• Aviation in World War II. Aircraft of France. / Aviation collection 10 /
• French Aircraft of World War II /Aviafrance./