Franklin O-425
The Franklin O-425 (company designation 6AG/6V6) was an American air-cooled aircraft engine that first ran in the mid-1940s. The engine was of six-cylinder, horizontally-opposed layout and displaced 425 cu in (7 L). The power output was between 240 hp (179 kW) and 285 hp (213 kW) depending on variant. The O-405-13 (6V6-300-D16FT) of 1955 was a vertically mounted, turbocharged and fan cooled version for helicopters.
| O-425/6AG/6V6 | |
|---|---|
| Type | Piston aircraft engine |
| National origin | United States |
| Manufacturer | Franklin Engine Company |
| First run | 1944 |
Variants
- 6AG6-245
- Geared propeller drive at 0.623:1, 245 hp (183 kW) at 3,300 rpm, (XO-425-5).
- 6AGS6-245
- Supercharged and geared, 250 hp (186 kW) at 3,200 rpm, (XO-425-3).
- 6V6-245-B16F
- Vertically mounted, fan-cooled helicopter version, 245 hp (183 kW) at 3,275 rpm, (XO-425-1).
- 6V6-300-D16FT
- Vertically mounted, turbocharged, fan-cooled helicopter version, 285 hp (213 kW) at 3,275 rpm, (O-425-13).
- O-425-1
- O-425-2
- O-425-3
- O-425-5
- O-425-9
- O-425-13
Applications
- Convair XL-13
- Republic YOA-15 (intended)
- Sikorsky S-52
- Sikorsky YH-18
Specifications (O-425-5)
Data from Aircraft engines of the World 1950.[1]
General characteristics
- Type: 6-cylinder air-cooled horizontally-opposed aircraft piston engine
- Bore: 4.75 in (120.7 mm)
- Stroke: 4 in (101.6 mm)
- Displacement: 425.3 cu in (6.97 l)
- Length: 47 in (120 cm)
- Width: 33.3 in (84.6 cm)
- Height: 30 in (76 cm)
- Dry weight: 405 lb (184 kg)
Components
- Valvetrain: 1 x exhaust and inlet OHV driven by pushrods and rockers
- Fuel system: 1 x Bendix-Stromberg PS-780 up-draught carburetor with automatic mixture control
- Fuel type: 80 Octane / US Army 2-103 all-purpose motor fuel
- Oil system: Pressure system at 55 psi (380 kPa)
- Cooling system: Air-cooled
Performance
- Power output:
- Take-off: 245 hp (183 kW) at 3,300 rpm
- Normal: 240 hp (180 kW) at 3,200 rpm at sea level
- Cruise: 168 hp (125 kW) at 2,840 rpm at sea level
- Specific power: 0.58 hp/cu in (26 kW/l)
- Compression ratio: 7.4:1
- Specific fuel consumption: 0.51 lb/hp/h (0.086 kg/kW/ks)
- Oil consumption: 0.015 lb/hp/h (0.0025 kg/kW/ks)
- Power-to-weight ratio: 0.606 hp/lb (0.996 kW/kg)
- Reduction gear: Planetary reduction gearing at 0.623:1
References
- Wilkinson, Paul H. (1950). Aircraft engines of the World 1950 (8th ed.). London: Sir Isaac Pitman & Sons Ltd. pp. 156–157.
Further reading
- Gunston, Bill (2006). World Encyclopaedia of Aero Engines (5th ed.). Stroud: Sutton Publishing. ISBN 978-0-7509-4479-3.
- Gunston, Bill (1989). World Encyclopaedia of Aero Engines (2nd ed.). Cambridge, England: Patrick Stephens Limited. ISBN 978-1-85260-163-8.
- Gunston, Bill (1993). World Encyclopedia of Aircraft Manufacturers. Annapolis: Naval Institute press. ISBN 9781557509390.
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