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

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
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See also

Comparable engines

Related lists

References
  1. 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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