Beta

The Ambrosini SAI.7
Type	Piston aircraft engine
National origin	Italy
Manufacturer	Isotta Fraschini
Developed from	Isotta Fraschini Gamma

The Isotta Fraschini Beta was an air cooled aircraft engine produced by the Italian engineering company Isotta Fraschini in the 1940s. Isotta Fraschini derived the Beta inverted 6-cylinder in-line aircraft engine from the V-12 Gamma. The engine saw limited production for aircraft, including the Nardi FN.316 and Ambrosini SAI.7, but was generally unsatisfactory in service.

Design and development

Isotta Fraschini had developed V-12 Gamma aircraft engine, which gained some success, powering the Ambrosini SAI.107 lightweight fighter.^[1] The company took essentially half of the engine and created the Beta inverted 6-cylinder in-line aircraft engine. The Beta shared the larger engine's bore and stroke. The engine had a one-piece aluminium alloy crankcase with steel and aluminium cylinders, each with a single inlet and a single exhaust valve. It had a carburettor designed by Isotta Fraschini and a single speed supercharger.^[2]

The Beta was produced in small numbers and fitted to a number of Italian training aircraft, including the Nardi FN.316 used in limited quantities by the Regia Aeronautica, Aeronautica Nazionale Repubblicana and German Luftwaffe during World War II.^[3] However, the engine was unsatisfactory in service, its failure leading to the cancellation of the IMAM Ro.63 STOL reconnaissance aircraft.^[4]

Variants

Beta R.C.10 ISZ: 300 hp (224 kW) for take-off 270 hp (201 kW) at 1,500 m (4,921 ft).^[2]

Applications

Specifications

Data from Wilkinson, 1945^[2]

General characteristics

Type: 6-cylinder air cooled inverted in-line aircraft piston engine
Bore: 125 mm (4.9 in)
Stroke: 130 mm (5.1 in)
Displacement: 9.6 L (586 in³)
Length: 1,625 mm (64.0 in)
Width: 410 mm (16 in)
Height: 800 mm (31 in)
Dry weight: 225 kg (496 lb)

Components

Valvetrain: Two valves per cylinder with overhead camshaft
Supercharger: Single stage, 10.0:1
Fuel type: 87 octane petrol
Cooling system: Air-cooled
Reduction gear: 0.79:1

Performance

Power output:
- (Take-off) 300 hp (224 kW) at 2700 rpm
- (Normal) 270 hp (201 kW) at 2500 rpm at 4,600 m (15,100 ft)
- (Cruising) 210 hp (157 kW) at 2200 rpm at 4,600 m (15,100 ft)
Specific power: 23.5 kW/L (0.51 hp/in³)
Compression ratio: 6.5:1
Fuel consumption: 320 g/(hp•h) (0.53 lb/(hp•h))
Oil consumption: 9.3 g/(hp•h) (0.02 lb/(hp•h))
Power-to-weight ratio: 1.00 kW/kg (0.61 hp/lb)

References

Notes

^ Thompson 1963, p. 15.
^ ^a ^b ^c Wilkinson 1945, p. 297.
^ Arena 1996, p. 325.
^ "Plane Facts: Italian Liaison STOL". Air Enthusiast. Vol. 2, no. 3. 1972. p. 150.
^ Thompson 1963, p. 46.
^ Thompson 1963, p. 13.
^ Brotzu, Caso & Cosolo 1977, p. 68.
^ Stocchetti 2009.

Bibliography

Arena, Nino (1996). L'Aeronautica Nazionale Repubblicana: la guerra aerea in Italia 1943-1945 (in Italian). Parma: Albertelli.
Brotzu, Emilio; Caso, Michele; Cosolo, Gherardo Cosolo (1977). Aerei Italiani nella 2ª Guerra Mondiale Vol.11, Scuola-Collegamento (in Italian). Roma: Edizioni Bizzarri. ISBN 978-8-8859-0949-6.
Stocchetti, Roberto (2009). "SAI Ambrosini 7, immagini, scheda e storia". Ali e Uomini (in Italian). Retrieved 8 September 2018.
Thompson, Jonathan (1963). Italian Civil and Military Aircraft, 1930-1945. Los Angeles: Aero Publishers. ISBN 1-2584-4296-5.
Wilkinson, Paul (1945). Aircraft Engines of the World. New York: P H Wilkinson.

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