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

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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