Bernard AB.1 / AB.2 / AB.3 / AB.4
The Adolphe Bernard AB 1 two engine biplane medium bomber, built near the end of the First World War, was the first original design from the Adolphe Bernard factory, which had previously produced SPAD aircraft to government contracts. It was a twin engine biplane bomber, carrying 600 kg (1,323 lb) of bombs.
Designed by Louis Béchereau, the AB 1 was a wooden three bay biplane, without stagger but with greater span on the upper planes. Only the lower wings carried dihedral. The outer and mid interplane struts were outward leaning pairs but the inner bay was defined by a complex of struts supporting the engines midway between the wings. Head on, these appeared as a V based on the lower wing but had M and W arrangements seen side-on above and below the engine. The AB 1 used Hispano-Suiza V-8 piston engines, of which type there was a surplus after the Armistice. It had ailerons on both upper and lower wings, externally connected.
The fuselage of the AB 1 was flat-sided, with a narrowed but flat topped decking. There was a gunner's position in the extreme nose fitted with a 7.7 mm machine gun on a TO 4 mounting. The fuselage tapered rearwards with the cantilever tailplane, which carried separate elevators, mounted on top. The fin carried a horn balanced rudder which extended down to the bottom of the fuselage, moving between the elevators.
Its main undercarriage had a wide track, with twin wheels on short axles mounted below each engine on inverted V struts, themselves further braced to the lower fuselage longerons.
The first AB 1 was built in 1918 and flew in the late spring of that yearand testing continued into early 1919. There were plans for a variant using more powerful Hispano-Suiza 8Ba engines, the AB 2, but this was not built. Post war, two civilian variants were started, the post-carrying AB 3 and the passenger only or passenger plus post AB 4. The AB 3, one of which was completed in 1920, could carry a useful load of 905 kg (1950 lb). The AB 4, which had the same engines as the proposed AB 2, carried a maximum of seven passengers. Its fuselage was on display at the 6th Paris Aero Show in December 1919, but it was not completed.
Ten AB 1s were produced after the Armistice but do not seem to have achieved squadron service.
AB 1
The bomber version of 1918, as supplied to the Armée de l'Air. Eleven built.
AB 2
Proposed version with 200 hp (150 kW) Hispano-Suiza 8Ba engines. Not built.
AB 3
Post carrying civil version of AB 1, two Hispano 180 hp engines. One built 1920.
AB.3 M 
Large twin boom monoplane bomber with three Hispano 12 G engines, two tractor and one pusher. One example started but unfinished.
AB.3 T 
Civilian transport derivative of the AB.3 M, with three tractor engines. Project only. 
AB 4
Airliner/post carrier version of AB 3, two Hispano 200 hp. Maximum seven passengers, depending on postal load. One part built 1919.
Engine: 2 × Hispano-Suiza 8 Ab, 130 kW (180 hp)
Propellers: 2-bladed (later 4)
Upper wingspan: 18.95 m (62 ft 2 in)
Length: 11.30 m (37 ft 1 in)
Height: 3.65 m (12 ft 0 in)
Wing area: 80.0 sq.m (861 sq ft)
Empty weight: 1,570 kg (3,461 lb)
Max takeoff weight: 2,859 kg (6,303 lb)
Maximum speed: 167 km/h (104 mph; 90 kn)
Cruising speed: 135 kph
Service ceiling: 4,900 m (16,076 ft)
Rate of climb: 2.1 m/s (410 ft/min) to 2,000 m (6,560 ft)
Armament: 7.7-mm machine gun
Bombload: 600 kg / 1,323 lb
Crew: 2