In 1928, the French Air Ministry issued a specification for a four-seat Multiplace de Combat, a multi-seat combat aircraft to act as a light bomber, reconnaissance aircraft and long-range escort fighter. Amiot received an order for two prototype Amiot 140s, to be evaluated against the competing Bleriot 137, Breguet 410 and SPCA 30.
The Amiot 140 was a high-winged cantilever monoplane of all-metal construction, with corrugated wing skinning and a fixed tail wheel undercarriage. The pilot sat in an open cockpit, with cockpits for gunners in the nose and dorsal positions. A glazed gondola under the forward fuselage carried a bombardier/gunner, ensuring that the gunners had a clear field of fire all around the aircraft.
The Amiot was intended to be powered by two 515 kW (690 hp) Lorraine 18G Orion water-cooled W engines but these were unavailable and the first prototype was fitted with Hispano-Suiza 12Nbr engines to allow flight testing, making its maiden flight on 12 April 1931. The second prototype was completed in February 1932 but the continued non-availability of its intended engines, either the original Lorraine-Dietrichs or turbocharged Hispano-Suizas, meant that it never flew. Despite this, on 23 November 1933 an order was placed for 40 Amiot 140s, to be powered by 662 kW (880 hp) Lorraine 12Q Eider engines.
The French Air Ministry had meanwhile revised its requirements, concentrating on the bombing role and asking for better performance. Amiot redesigned the aircraft to meet these requirements and incorporate lessons learned during testing of the Amiot 140.
The gondola under the fuselage was enlarged, allowing easier operation of the aircraft's guns and a fifth crew member (a radio-operator) to be carried. Manually operated gun turrets were provided in the nose and dorsal positions.
Orders were placed for two prototypes, differing only in the engines fitted, with the Amiot 142 having Hispano-Suiza 12Y engines and the Amiot 143 having Gnome-Rhone 14K radial engines. The 143 flew first, on 1 August 1934, with the 142 not flying until January 1935. As it was decided to allocate the Hispano-Suiza engines to fighters, the Amiot 143 was selected, the existing order for 40 Amiot 140s being converted to 143s.
The Amiot 143 had the same high-wing and fixed undercarriage as the Amiot 140, with the wing thick enough to allow crew access to the engines by a tunnel between the wing spars. The pilot sat in an enclosed cockpit, level with the leading edge of the wing and the navigator-bombardier, who was also provided with flying controls, sat in the extensively glazed gondola beneath the pilot. The radio operator sat towards the rear of the gondola and in early aircraft operated two 7.7 mm Lewis guns.
Nose and dorsal turrets, each carrying a Lewis gun, completed the defensive armament, while the gondola also housed an internal bomb-bay. After 40 aircraft had been completed, the design was revised, with the aircraft being fitted with a longer nose (increasing overall length from 17.94 m to 18.24 m, a revised fuel system and with the Lewis guns in the nose, dorsal turrets and ventral position replaced by single 7.5 mm MAC 1934 machine guns, with a fourth gun used by the navigator-bombardier firing through a hatch in the floor.
Deliveries of the aging design eventually began in April 1935, continuing until March 1937, with a total of 138 being built. An improved version, the Amiot 144 was built to meet 1933 requirement for a Multiplace de Combat, combining the same fuselage and a similar wing with a retractable undercarriage. First flying on 18 January 1936, only one was built.
Crew: Five (pilot, navigator/bombardier, radio operator, nose and dorsal gunners)
Length: 18.24 m
Wingspan: 24.53 m
Height: 5.68 m
Wing area: 100 m2
Empty weight: 5,455 kg
Gross weight: 8,611 kg
Max takeoff weight: 10,360 kg
Powerplant: 2 × Gnome et Rhône 14Kirs/Kjrs 14-cyl. air-cooled radial engines (counter-rotating), 640 kW (858 hp) each
Maximum speed: 295 km/h
Range: 1,300 km
Ferry range: 1,995 km
Service ceiling: 7,500 m
Time to altitude: 2,000 m in 6.8 minutes
Guns: 4× 7.5 mm MAC 1934 machine guns (one each in nose and dorsal turrets, forward gondola and rear gondola)
Bombs: 800 kg internally plus 800 kg externally
The Amiot 143M entered service in July 1935, with deliveries continuing in 1936 and 1937. About six were going to be delivered to the Spanish Republican Air Force at the beginning of the Spanish Civil War. There is no evidence, however, that these obsolete French bombers flew over Spain during the Civil War.
By the time the last deliveries were made in March 1938, the Amiot was quite out of date and began to be replaced by modern aircraft such as the Bloch MB.131. Nevertheless, at the outbreak of the Second World War, Amiot 143s equipped 5 metropolitan groupes together with a single African based groupe.
During the Phoney War, Amiot 143M groupes carried out reconnaissance and leaflet raids over Germany. 87 Amiot 143M remained in front line service on 10 May 1940, 50 equipping four metropolitan groupes: GBs I/34 and II/34 in the north, GBs I/38 and II/38 in the East and 17 equipping one African groupe, GB II/63, which was in the process of re-equipping with Martin 167Fs.
Following the start of the Battle of France, the Amiot 143M was mainly used in night attacks against German airfields and lines of communications, with losses relatively low. One notable exception was a daylight raid by 10 Amiots from GBs I/34, II/34 and II/38 led by Commandant de Laubier against German bridgeheads near Sedan on 14 May 1940. Despite fighter escort, two Amiots were shot down while a third force-landed before reaching its base.
By the Armistice, the Amiot 143M had dropped a total of 474 tonnes (523 tons) of bombs. 52 Amiot 143Ms were in the Unoccupied Zone and 25 were in French North Africa. They were reorganized into GBs I/38 and II/38 and were used until July 1941 when they were replaced by LeO 451 bombers.
Some planes of II/38 served as a transports for the French in Syria. This groupe later went over to the Allies after their landings in Africa. The last Amiot 143M was retired from service in February 1944.
A few Amiot 143M are reported to have been commandeered by the Germans and used as transports. Only 11 were left in the Unoccupied Zone when it was occupied by the Germans in 1943 and only three were flightworthy.
Had the war gone on a little longer for France, it is likely that all of the Amiot 143M would have ended up in a training role, having been replaced by more modern bombers such as the Breguet 693. The obsolete plane was never intended to have such an important role come war time, but slow French production made its use necessary - often being pulled from training squadrons to shore up bomber groupes.