The Bloch MB 210, which has a family resemblance with its predecessor, the Bloch MB 200, was originally the response to a Navy requirement for a heavy torpedo bomber in 1932.
The Marcel Bloch company began working on a response to the Navy requirement in 1933, using its own funding. The MB 210 adopted the same construction principles that had been developed for the MB 200. It was an all-metal low-wing cantilever monoplane. The fuselage was built as a single assembly around four angle longerons, frames and a sheet metal skin. It had a rounded rectangular cross section. The totality of the metallic skin was stiffened by U-section stringers, giving the entire airframe its characteristic appearance.
Construction of two prototypes was started in Courbevoie. MB 210 n° 01 was transferred to Villacoublay on 27 July 1934, and the first flight, with André Curvale at the controls, took place on 24 November. The aircraft was equipped with a fixed trousered undercarriage and two 760hp Gnome-Rhône 14 Kdrs/grs engines.
Unable to identify an application for such an aircraft in its land-based form, the Navy asked the Marcel Bloch company to transform its MB 210 BN4 n° 1 into a twin-float seaplane. The prototype was sent to Marignane to be modified accordingly.
The first water takeoff reportedly occurred in January 1936 on the étang de Berre. The aircraft was then delivered to the Saint Raphaël test centre on 26 February 1937. Testing revealed that the performance of MB 210 n° 1 was inadequate and its range insufficient for a torpedo bomber.
MB 210 n° 1 was purchased by the Navy and assigned to Saint Raphaël, under the code SR-25 (SR for Saint Raphaël) until 1940.
The series production float version, designated MB 218, was never delivered despite an order for eight units from SNCASO in 1937.
Anxious to modernise its equipment in light of Germany’s rapid rearmament, the French Air Force, having monitored the tests of the first prototype, decided that the MB 210 offered substantially improved performance compared with the bombers in service at the time (LeO 20, Bloch 200, etc).
It was therefore decided to launch series production of the aircraft under Plan I, and the first MB 210 for the Air Force, though very different from the amphibious prototype, was also designated n° 1.
The aircraft made its first flight on 12 December 1935 and was handed over to the CEMA test centre on 27 January 1936.
On completion of testing, a number of series production orders were issued under several contracts in 1935-1937 and the majority of French aircraft manufacturers built the aircraft under licence. A total of 298 aircraft (including the 24 for Romania, of which only 10 were actually delivered, plus 10 whose fate is unknown) were built through 1939. It is reported that a certain number of aircraft, without factory numbers, were built by Hanriot for republican Spain. The only confirmed aerial delivery was the n° 1 aircraft, flown by Lionel de Marinier on 26 August 1936. Three other MB 210s built by Hanriot were delivered in crates at the end of October 1936. The first of these, for a time, was part of the squadron formed by André Malraux.
Flight crews had problems with the aircraft, due to its innovative features (retractable undercarriage, variable pitch propellers, landing speed), and the Gnome-Rhône 14-Kirs/jrs engines showed some notable shortcomings. The problems with the engines eventually led to the aircraft being refitted with Gnome-Rhône 14N 10/11 (or N 20/21) engines offering 910hp takeoff power. Aircraft handling was satisfactory, despite numerous accidents, highlighted by the press, which were often due to the crew, in addition to the engines.
At the outbreak of war in September 1939, the MB 210 was in service with 12 of the 33 Air Force bomber groups. GB II/21 received the first production aircraft in 1936. The other units using the aircraft were: GB I/II, II/11l, I/12, II/12, I/19, II/19, I/21, II/21, I/23, II/23, I/51 and II/51. Used for day and night operations, the aircraft were soon declared unsuitable for war missions. The units involved were progressively pulled back for conversion to the LeO-45 or Amiot-351, and the aircraft were withdrawn or redeployed to flight schools. A total of seven aircraft were lost during operations: five shot down in combat and two in accidents. Three were destroyed by German bombardments, and nine were scrapped after sustaining damage in combat.
After the armistice, a total of 120 MB 210s were present in the non-occupied zone, with 20 in North Africa. 37 were captured by the Germans in 1942, including six that went to Bulgaria, where their fate is unknown.
In parallel with MB 210 n° 1, a second prototype was built, designated MB 211 n° 1 and baptized “Verdun”. The main difference between the two aircraft was in the propulsion area; the latter was equipped with 860hp Hispano-Suiza 12Ybrs-1 engines. This all-aluminium aircraft, strangely carrying naval aviation markings, was displayed at the Air Show in November 1934. The MB 211 was ferried to Villacoublay on 8 December 1934 and made its first flight on 29 August (16 April?) 1935. The change of engine did nothing to improve performance, and the prototype did not receive a series production contract. The aircraft remained the property of the Marcel Bloch company, which replaced the engines with 940hp Hispano-Suiza 14 Aa 00/01s. Redesignated MB 212 n° 01, it was soon abandoned.