Fiat AS.6
| Industry | Aerospace, Automotive |
|---|---|
| Founded | 1899 in Italy |
| Headquarters | Italy |
| Products | Aircraft engines, automobiles |
The Fiat AS.6 was a distinctive Italian liquid-cooled, V-configured piston aero engine featuring 24 cylinders, conceived and constructed by Fiat in the late 1920s specifically for participation in the Schneider Trophy air races. Despite its innovative design, persistent developmental and operational challenges prevented it from competing successfully. Nevertheless, after overcoming initial difficulties, the engine powered a seaplane to a piston-engine speed record that remains unbroken to this day.[1]
Design and development
For the 1931 Schneider Trophy competition, the Italian entrant, the Macchi M.C.72, demanded an engine capable of delivering 2,300 horsepower (1,700 kW) with potential output reaching 2,800 horsepower (2,090 kW), while keeping weight below 840 kilograms (1,850 lb). Fiat secured the contract but faced a significant challenge as their most potent V engine at that time was the 1,000-horsepower (750 kW) 12-cylinder Fiat AS.5, which had also been employed in Schneider Trophy efforts.
To meet these requirements, Fiat devised an innovative approach by coupling two AS.5 V12 engines in tandem to create a V-24 configuration. Each engine independently powered one of a pair of contra-rotating propellers via coaxial shafts.[2] Rather than a conventional V24 where all cylinders drive a single crankshaft, this setup functioned more as a "tandem V12" with two separate crankshafts rotating in opposite directions and driving independent shafts without gearing them together for a unified output. The rear engine transmitted power to the forward propeller through a reduction gearbox situated between the two engines and connected by a shaft running between the cylinder banks of the forward engine, which was mounted in reverse orientation. Conversely, the front engine's crankshaft faced rearwards and drove the aft propeller through a hollow shaft that allowed passage of the rear engine’s driveshaft.[3] A large centrifugal mechanical supercharger was installed at the rear to boost performance, with the fuel-air mixture delivered via a centrally positioned manifold located between both engines’ cylinder banks.[2]
This configuration offered benefits such as maintaining a minimal frontal area and leveraging Fiat’s prior experience with the AS.5 design. With an aggregate displacement of 50 litres (3,066 cu in), it was anticipated that the power goals would be achieved without difficulty.[4]
However, technical difficulties plagued the AS.6 during development, preventing Italy’s team from participating in the 1931 Schneider Trophy race. Eventually, on 23 October 1934, after resolving backfiring issues with assistance from British engineer "Rod" Banks, pilot Francesco Agello used the AS.6 to establish a new piston-powered seaplane speed record of 709.2 kilometres per hour (440.6 mph), which remains unbeaten.[1]
Applications
Engines exhibited
- A Fiat AS.6 engine is showcased at the Italian Air Force Museum.
- An additional AS.6 engine can be found on exhibit at the Centro Storico Fiat located in Turin, Italy.
Specifications (AS.6)
See also
Notes
Bibliography
- Eves, Edward The Schneider Trophy Story. Shrewsbury. Airlife Publishing Ltd., 2001. ISBN 1-84037-257-5.
- Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
