Franklin O-425

{{Short description|American piston aircraft engine}} {{Use dmy dates|date=December 2022}} {{Use American English|date=December 2022}}  {{infobox aero engine |name= O-425/6AG/6V6 |image = |caption = |engine_type= [[Piston]] [[aircraft engine]] |national_origin = United States |manufacturer= [[Franklin Engine Company]] |first_run= 1944 |major_applications= |number_built = |developed_from = |developed_into = |variants_with_their_own_articles = }}

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 [[Flat-six engine|six-cylinder, horizontally-opposed layout]] and [[Engine displacement|displaced]] {{convert|425|cuin|L|abbr=on|0}}. The power output was between {{convert|240|hp|kW|abbr=on|0}} and {{convert|285|hp|kW|abbr=on|0}} depending on variant. The '''O-405-13 (6V6-300-D16FT)''' of 1955 was a vertically mounted, [[Turbocharger|turbocharged]] and fan cooled version for helicopters.

==Variants== ;6AG6-245:Geared propeller drive at 0.623:1, {{convert|245|hp|kW|abbr=on|0}} at 3,300 rpm, (XO-425-5).

;6AGS6-245:Supercharged and geared, {{convert|250|hp|kW|abbr=on|0}} at 3,200 rpm, (XO-425-3).

;6V6-245-B16F:Vertically mounted, fan-cooled helicopter version, {{convert|245|hp|kW|abbr=on|0}} at 3,275 rpm, (XO-425-1).

;6V6-300-D16FT:Vertically mounted, turbocharged, fan-cooled helicopter version, {{convert|285|hp|kW|abbr=on|0}} 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== *[[Stinson L-13|Convair XL-13]] *[[Republic RC-3 Seabee|Republic YOA-15]] (intended) *[[Sikorsky S-52]] *[[Sikorsky S-52|Sikorsky YH-18]] *[[Stinson L-13]]

==Specifications (O-425-5)== {{pistonspecs |  |ref=''Aircraft engines of the World 1950.''<ref name=AEotW50>{{cite book |last=Wilkinson |first=Paul H. |title=Aircraft engines of the World 1950 |year=1950 |publisher=Sir Isaac Pitman & Sons Ltd. |location=London |edition=8th |pages=156–157}}</ref> |type=6-cylinder air-cooled [[horizontally-opposed]] aircraft piston engine |bore={{cvt|4.75|in|1}} |stroke={{cvt|4|in|1}} |displacement={{cvt|425.3|cuin|L|2}} |length={{cvt|47|in|cm}} |diameter= |width={{cvt|33.3|in|cm|1}} |height={{cvt|30|in|cm}} |weight={{cvt|405|lb}} |valvetrain=1 x exhaust and inlet OHV driven by pushrods and rockers |supercharger= |turbocharger= |fuelsystem=1 x Bendix-Stromberg PS-780 up-draught carburetor with automatic mixture control |fueltype=[[80 Octane]] / US Army 2-103 all-purpose motor fuel |oilsystem=Pressure system at {{cvt|55|psi}} |coolingsystem=Air-cooled |power=<br> :*'''Take-off:''' {{cvt|245|hp}} at 3,300 rpm :*'''Normal:''' {{cvt|240|hp}} at 3,200 rpm at sea level :*'''Cruise:''' {{cvt|168|hp}} at 2,840 rpm at sea level |specpower={{cvt|0.58|hp/cuin|kW/L}} |compression=7.4:1 |fuelcon= |specfuelcon={{cvt|0.51|lb/hp/h}} |oilcon={{cvt|0.015|lb/hp/h}} |power/weight={{cvt|0.606|hp/lb}} *'''Reduction gear:''' Planetary reduction gearing at 0.623:1 }}

==See also== {{aircontent  |see also= |related= |similar engines= *[[Continental O-470]] *[[Lycoming O-480]] |similar aircraft= |lists= *[[List of aircraft engines]] }}

==References== {{reflist}}

==Further reading== * {{cite book |last=Gunston |first=Bill |title=World Encyclopaedia of Aero Engines |publisher=Sutton Publishing |location=Stroud |year=2006 |edition=5th |isbn=978-0-7509-4479-3 }} * {{cite book |last=Gunston |first=Bill |title=World Encyclopaedia of Aero Engines |year=1989 |publisher=Patrick Stephens Limited |location=Cambridge, England |isbn=978-1-85260-163-8 |edition=2nd }} * {{cite book |last=Gunston |first=Bill |title=World Encyclopedia of Aircraft Manufacturers |publisher=Naval Institute press |location=Annapolis |isbn=9781557509390 |url=https://archive.org/details/isbn_9781557509390 |year=1993 }}

[[Category:Franklin aircraft engines]] [[Category:1940s aircraft piston engines]] [[Category:Boxer engines]] [[Category:Six-cylinder engines]] [[Category:Air-cooled aircraft piston engines]]