Evolved in parallel with the CR.33 but completed and flown earlier owing to engine availability, the CR.40 was powered by a radial air-cooled engine, unlike the preceding Fiat fighters.

The prototype CR.40 was flown in March 1934 with a 550 hp Alfa Romeo-built Bristol Mercury I engine. Provision was made for two synchronised 12.7mm machine guns and the structure was of steel and light alloy with fabric skinning.

The CR.40 attained a maximum speed of 234 mph / 377 kph and reached an altitude of 9840 ft / 3000 m in 6.83 minutes, but climbing qualities and stability proved inferior to those of the CR.32.

A second prototype, the CR.40bis, also tested in 1934, differed only in having a Fiat A 59 R (a licence-built P&W Hornet) engine rated at 690 hp at 6560 ft / 2000 m and driving a flight-variable two-pitch propeller.

The CR.40 indirectly led to the production CR.42.

CR.40bis
Engine: Fiat A 59 R, 690 hp
Wingspan: 30 ft 6 in / 9.30 m
Length: 22 ft 10 in / 6.96 m
Height: 8 ft 6 in / 2.60 m
Wing area: 224.97 sq.ft / 20.90 sq.m
Empty weight: 2645 lb / 1200 kg
Loaded weight: 3748 lb / 1700 kg
Max speed: 241 mph / 388 kph at 6560 ft / 2000 m
Endurance: 1.83 hr

A derivative of the CR.32 designed to take the 690 hp A 33 RC 35 supercharged engine, the CR.33 differed little externally from its predecessor but had marginally larger overall dimensions and was fitted with a ground-adjustable three-blade propeller. Armament comprised two fuselage-mounted 12.7mm guns and two wing-mounted 7.7mm weapons, and an internal bay could accommodate either 12 x 4.4 lb / 3 kg anti-personnel bombs or camera equipment. Although the Fiat A 33 RC 35 engine was completed in 1935, difficulties with this engine delayed prototype trials of the CR.33 until 1937, by which time the air-cooled radial engines were officially favoured for fighter installation, and the development programme was restricted to three prototypes.

Engine: 690 hp A 33 RC 35
Span: 32 ft 2 in / 9.80 m
Length: 24 ft 9.5 in / 7.56 m
Height: 8 ft 6 in / 2.60 m
Wing area: 241.11 sq.ft / 22.40 sq.m
Empty weight: 2998 lb / 1360 kg
Loaded weight: 4211 lb / 1910 kg
Max speed: 262 mph / 422 kph
Max range: 435 mi / 700 km