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FIAT A 74 R1C 38 Ciclone
1935 - primi anni '40



The FIAT A.74 Ciclone is a twin-row, radial aircraft engine with 14 cylinders, with a max. power of 940 hp. Before the 1930’s FIAT mainly developed liquid-cooled aircraft engines so the FIAT A 74 and the FIAT A 80 have been the first high power air-cooled airplane engines produced by FIAT in the 30’s. These engines, produced in various version, have been derived from a Pratt and Whitney model and have been then developed by FIAT with several original design improvements. Despite they have been produced in a large number up to the first part of the 1940’s, due to several reasons, only few specimen survived up to nowadays. These engines have been widely used for many aircrafts up to the 1940’s, mainly in military aircrafts.

Technical specifications

ManufacturerFIAT Aviazione, Turin, Italy, from 1935 up to early 1940s
TypeA 74 R1C 38 Ciclone
Descriptiontwin-row 14-cylinder radial engine, crankcase, heads and pistons made of aluminium-alloy, streel-made cylinders screwed into the heads, hemispherical combustion chambers, crankshaft composed of two parts connected by bolts
Stroke145 mm
Bore140 mm
Displacement31250 cm³
Compression ratio6.7
Power840 hp (standard output) at 2400 rpm, at 3800 m with an absolute intake manifold pressure of 1.00 bar
Specific fuel consumption270 g/hp/h
Specific power26.9 hp/litre
Valvetrain system2 overhead valves per cylinder, operated by pushrods and rocker arms, with exhaust sodium-cooled valves
Fuel feeding systemwith one single-barrel gasoline Zenith-Stromberg carburetor, placed upstream of the compressor and equipped with pressure limiter and air-fuel mixture preheating
Supercharging systemwith a single-stage centrifugal compressor, driven by the crankshaft by means of a spur gears drive with a speed ratio of 8.78:1, for a full-throttle height of 3800 m
Ignition systemtwo spark plugs per cylinder fed by two independent Marelli magneto distributors
Cooling systemair-fed
Lubrication systemforced by gear pumps
Starting systemcompressed air type with a 12 litres tank at a max. pressure of 15 bar (sufficient for 2 starts) and a Garelli air compressor for re-charging
Weight590 kg
Mass-to-power ratio0.70 kg/hp
Propeller speed ratio0.725:1 by means of a Farman-type bevel gear epicyclic reducer (the standard version RC.38 has a reduction ratio 0.655:1)


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Testi e immagini di Giuseppe Genchi
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