Franklin, Aircooled Motors, Doman-Marks (US);
Franklin Aircraft Engines, WSK-PZL (Poland)

Part 1: Introduction and O-110 through O-300



This is the first part of the Franklin engine compilation. All of the introductory material is contained here, as well as the compilations of the engines with smaller displacement, namely from the O-110 (2A-110) through the O-300 (6AC-298). The second part of the Franklin compilation, namely from the O-315 (6AL-315) through the O-805 (12AC-596) can be reached here.


H.H. Franklin Co., of Syracuse, New York, which produced the Franklin automobiles with air-cooled engines, went out of business in 1935. From there, the story is reported somewhat differently by the aircraft-engine literature (Jane's, S, BGE, PMB, AY) and the automotive literature (K&C).

Aircraft engine sources report that a group of Franklin engineers, led by Carl T. Doman and Edward S. Marks, bought the assets at a bankruptcy sale and formed Aircooled Motors Development Co. Aircooled Motors, also located in Syracuse, developed the Franklin line of aircraft engines from 1938 through WW II. In Oct. 1945, Aircooled Motors was purchased by Republic Aircraft Corp. to ensure sufficient production of the O-500 (6A8-215) engine for the RC-3 Seabee. The acquisition was followed by an order for 5,000 engines for the Seabees (AY46). No prewar engine designs were built postwar, but late-war and early postwar designs were manufactured. Seabee production ended in 1947 after 1,060 were built. Tucker Industries purchased Aircooled in March 1948 to develop and produce the engines for the 1948 Tucker automobile discussed below. Aircooled remained busy throughout the 1950's and was the only profitable operation of Tucker. However, no completely new aircraft engine development was undertaken during the later years of Tucker ownership. Tucker sold Aircooled in 1961 to Aero Industries, Inc. which renamed it Franklin Engine Co., Inc. as part of the group that included the resurrected Waco company name to market French light planes. The Franklin organization then had the resources again to develop and produce a new series of engines that continued until 1974, when Franklin was purchased by Audi, S.A. of Brazil. Audi, in turn, sold the assets, designs, and tooling, including many of the FAA Type Certificates, to the WSK-PZL group in Poland during 1975.

Polish production of Franklin engines continued until 2002 when WSK-PZL facilities were purchased by United Technologies Corp. (UTC) of the US in order to increase production capability for Pratt & Whitney (Canada). PZL had been a production sub-contractor for P&W (Canada) for more than 25 years. Apparently, the Franklin piston-engine Type Certificates and tooling owned by WSK-PZL were not part of the UTC deal. The TCs and tooling have been sold to a Polish group headed by Roman Sadowski. This group has formed the Franklin Aircraft Engines firm in Grudziqdz, Poland. Maciej Smolinski is the Manager of the firm, which claims to have obtained Production Certification by the FAA in the US. Production Certification gives the firm itself the capability of supervising and approving all production engines and parts which they manufacture. Initial production is underway, but is limited, for now, to manufacturing much-needed spare parts for the most widely used Franklin engines, namely the O-335 and O-350. The firm has had some exposure in the US, especially at Oshkosh in 2007. Their plans are to resume production of the O-235 (4A-235), O-335 (6A-335-B2), and O-350 (6A-350-C1R) at some later time.

The new Franklin Aircraft Engines firm in Poland is developing a Website, which includes a brief history of Franklin automobiles and the later aircraft engines by Aircooled Motors. Additional contemporary information about Franklin engines and their future can be found at a Website for Stinson Model 108 owners. On that site, click first on "Stinson" and then on "Stinson Engine Options".

According to an automotive source (K&C, pp. 20-21), Doman and Marks, formerly of Franklin, formed Doman-Marks Engineering Company. In 1937, D-M designed a 126 cu.in., 50hp, horizontally-opposed air-cooled engine to be installed in Airomobile Co.'s 3-wheeled "streamlined" car. The Airomobile car was unsuccessful, but the engine was enlarged and developed further for light planes, apparently into the O-150 (4AC-150) by Doman-Marks. This source also says that Doman-Marks was purchased by Republic before WW II and then sold by Republic to the Tucker Co. post-WW II. This report (K&C) is generally consistent, but the Republic purchase date apparently is in error as described above.

It is of interest to automobile enthusiasts that the engine used as the basis for the 1948 Tucker automobile engine was the Franklin O-335 (in its 6V4-178 or 6V4-200) air-cooled helicopter-engine version. Franklin and Tucker converted the air-cooled O-335 into an engine with a fully-sealed liquid-cooling system for the 1948 Tucker. Information on the 1948 Tucker and its engine can be found in many automobile books and on the Tucker Club Website. An interesting aeronautical side light is that one of these liquid-cooled Tucker auto engines found its way into the Waterman Aerobile [N54P] flying auto [AAHSW66].

Distributor in the US for the Franklin engines built by WSK-PZL in Poland is:

Franklin Aircraft Engines, Inc. of Fort Collins, Colorado

The Franklin Aircraft Engines of Colorado is their Website. This firm holds Supplemental Type Certificates for the following (US) aircraft. The O-350 (6A-350) can be used on Cessna 170 series, 172 series, 175 series, and Stinson 108 series aircraft {see their Website for the models eligible for this engine (both landplane and floatplane versions)}. They also provide Firewall-Forward Kits for some popular experimental, homebuilt kit aircraft as follows; the O-235 (4A-235) for the (US) Skystar Kitfox Models 5, 6, and 7, and the O-350 (6A-350) for the (Canada) C.L.A.S.S. Bush Caddy L164, and the (US) Van's RV-8, -8A and Zenith CH-801.

Firms that offer Restoration, Service, and Parts for Franklin engines include:

Bobby @ Franklin Parts and Service
2756 W. Fairview Rd.
Underwood, IN 47177
(812) 752-6919

Greg Lucas' Website

Some Technical Observations:

(1) Fuel injection in the intake manifold at each cylinder of Franklin engines was offered as an option only on the later versions of the O-235 and O-335.

(2) Before WWII, many Franklin models had geared versions as an alternative to direct drive, although many of the geared versions did not receive type certificates. The gear ratio (propeller rpm divided by the engine crankshaft rpm) is presented where known. The prewar O-400 and O-595 engines had geared versions that could be shifted to direct drive for cruise. Franklin announced after WWII, when their prewar engines were discontinued, that none of their new postwar engines would be offered in geared versions. They believed that the cost at that time was too great for light commercial aircraft. They deviated from this only in offering a few geared versions of their higher-powered O-335 engine family.

(3) During WWII and throughout the 1950s and 1960s, Franklin specialized in helicopter engines. Versions of their engines were offered for horizontal mounting and vertical mounting, with or without auxiliary fan cooling.

(4) All families of Franklin horizontally-opposed aircraft engines are listed in the table of Franklin Engine Families. This table gives a compact reference to their chronological and technical development.

As an aid for those who are familiar with the various Franklin designation systems, the following Table of Equivalence is given so that the desired engines can be found easily:

Manufacturer's DesignationWebsite Designation
2A4-45, -49, 2A-110, 2AL-112O-110
2A-120O-120
4AC-150O-150
4AC-171O-170
4AC-176, 4ACG-176O-175
4AC-199, 4ACG-199O-200
4A4-75, -85, -95, -100, 4A-225, 4AL-225O-225
4A-235, Sport 4O-235
6AC-264, 6ACG-264O-265
6AC-298, 6ACG-298, 6ACT-298, 6ACTS-298, 6ACV-298O-300
6A3, 6AL-315, 6ALG-315O-315
6A4-125, -130, -135, -140, -145, -150, -165, -200, 6V4-165, -178, -200, -335, 6AG4-185, 6AL-335, 6ALV-335, 6A-335, 6AG-335, 6AGS-335, 6AS-335, 6V-335, 6VS-335O-335
6A-350, 6AS-350, 6V-350O-350
8AC-398, 8ACG-398O-400
6AC-403, 6ACSA-403, 6ACGA-403, 6ACV-403O-405
6ACV-245, 6AG6-245, 6AGS6-245, 6V6-245, -300O-425
6A8-215, 6AL-500O-500
8ACG-538, 8ACGSA-538, 8ACSA-538O-540
12AC-596, 12ACG-596O-595
12AC-806, 12ACG-806, 12ACGSA-806O-805
Sport 4, 4A-235O-235



O-110 - - {4.5 / 3.5 / 111.3} / {114.3 / 88.9 / 1824}

Same bore and stroke as O-225, O-335.
Same stroke as O-120, O-175, O-200, O-235, O-265, O-300, O-315, O-350, O-400, O-595.
2A4 series are the two-cylinder versions of the 4A4 (O-225), 6A4 (O-335) series.

2cyl; 2A4-45, 2A4-49; 45hp@2650rpm-49@3000; 1944-1947; Wt = 116#; TC = 240 in c.1945 - expired 12/5/50.
Franklin also called these the 2AL-112 for their displacement.
FAA Website.
Applications: (US) Lockheed Little Dipper [NX18935].

2cyl; 2A-110; 60hp@3000rpm; 1962; Wt = N/A; TC = none.
Relationship to the 2A4 is unknown. It was a two-cylinder engine introduced in 1962 to broaden the product range and was developed into the 2A-120 (O-120) with an increase in bore. See, also, the 4A-225 (O-225) and 6A-335 (O-335).
J62-63; W62-63.
Applications: None found.


O-120 -- {4.625 / 3.5 / 117.6} / {117.5 / 88.9 / 1927}

Same bore and stroke as O-235, O-350.
Same stroke as O-110, O-175, O-200, O-225, O-265, O-300, O-315, O-335, O-400, O-595.
Developed from 2A-110 (O-110) with an increase in bore. Sold to WSK in 1975 and produced by PZL.

2cyl; 2A-120; 60hp@3200rpm; 1964-2002; Wt = 126-133#; TC = 24EA on 4/26/71.
J64-65toJ75-76 under Franklin; J76-77 to present under WSK-PZL; S.
Applications: (Germany) Sportavia (Fournier) RF5S motorglider. (Poland) WSK-PZL Kosno KR-02; PZL-126 Mrwka light agplane. (UK) Wallis WA-116/F, WA-121/F gyroplanes. (US) Bellanca 7ACA Champion. (Yugoslovia) VTC SSV-17 motorglider.


O-150 -- {3.625 / 3.625 / 149.6} / {92.1 / 92.1 / 2452}

Same stroke as O-170.
Single- and dual-ignition versions were available.
White Truck Co. also used versions of this engine in their "White Horse" standup delivery trucks (S).

4cyl; 4AC-150; 40hp@1875rpm-60@2400; 1938-1941; Wt = 158-166#; TC = 194 on 3/10/38 - expired 7/11/41.
aerofiles.com (for applications); Ae39; AY40; Fahey USAAF; H&H (for Aeronca applications); J7, J8; S.
Applications: (UK) Clutton-Tabenor FRED Series 2 [G-ASZY]. (US) Aeronca 50-F, CF & KF Chiefs, 50-TF Trainer; Fetterman Chickadee; Payne MC-7 pusher [NX18238]; Piper J-3F-40, -50 Cubs; Rose A-2F Parrakeet [NC18252]; Taylorcraft BF, L-2E, L-2G, L-2K, L-2L.


O-170 -- {3.875 / 3.625 / 171.0} / {98.4 / 92.1 / 2802}

Same stroke as O-150.
Single- and dual-ignition versions were available.

4cyl; 4AC-171; 60hp@2350rpm; 1939-1941; Wt = 159-169#; TC = 206 on 2/10/39 - expired 7/11/41.
aerofiles.com (for applications); Ae39; H&H (for Aeronca applications); J7, J8; S.
Applications: (US) Aeronca 50-F Chief, 60-TF Trainer; Jensen 3-LW Sport [NX18157]; Piper J-3F-65 Cub, J-4B Cub Coupe, P-2 (a 1941 prototype) [NX33281]; Porterfield FP-60 Collegiate; Rose A-3F Parrakeet; Taylorcraft BF-60.


O-175 -- {4.0 / 3.5 / 175.9} / {101.6 / 88.9 / 2883}

Same bore and stroke as O-265.
Same stroke as O-110, O-120, O-200, O-225, O-235, O-300, O-315, O-335, O-350, O-400, O-595.

4cyl; 4AC-176-B, -C; 65hp@2300rpm-75@2500; 1940-1945; Wt = 182-189#; TC = 221 in c.1940 - expired 12/5/50.
Military O-175-1 was 4AC-176-BA2 (65@2300); note Military designation change between this and 4AC-176-D, -F.
aerofiles.com (for applications); Ae41toAe43; AMC; AY40, 41; Fahey USAAF; H&H (for Aeronca applications); J7, J8; J41toJ45-46; W41toW45.
Applications: (Brazil) C.A.P. 4 Paulistinha, 4B Ambulancia, 4C Paulistinha Radio; I.P.T. 7 Junior. (US) Aeronca 65-TF, 65-TAF, L-3D; Bowyer BW-1 flying wing; Harris Little Jewel [N7936A]; Interstate S1A-65 Cadet; Langley Twin 2-4-65; Piper J-3F-65 Cub, J-4B Cub Coupe, L-4D; Porterfield FP-65 Collegiate; Taylorcraft BF-65, DF-65, BF-12-65.

4cyl; 4AC-176-D, -F; 80hp@2500, 2650rpm; 1940-1945; Wt = 183-218#; TC = 221 in c.1940 - expired 12/5/50.
Military O-180-1 was 4AC-176-F3 (80@2500); note Military designation change between this and 4AC-176-B, -C.
aerofiles.com (for applications); Ae41toAe43; AMC; AY41; J7, J8; J41toJ45-46; W41.
Applications: (US) Culver LFA Cadet; Payne KT-80 Knight Twister; Rearwin 180F Skyranger; Vought-Sikorsky VS-300 (intermediate version of Sikorsky's first successful helicopter) [NX28996].

4cyl; 4ACG-176; 94hp@3100rpm; 1940-1943; Wt = N/A; TC = none.
Geared to N/A.
W41.
Applications: None found.


O-200 -- {4.25 / 3.5 / 198.6} / {108.0 / 88.9 / 3254}

Same bore and stroke as O-300, O-400, O-595.
Same stroke as O-110, O-120, O-175, O-225, O-235, O-265, O-315, O-335, O-350.

4cyl; 4AC-199; 65hp@1950rpm-90@2500; 1941-1945; Wt = 190-233#; TC = 226 in c.1941 - expired 12/5/50.
Military O-200-1, -3, -7, -9 (90@2500).
aerofiles.com (for applications); Ae41toAe43; AMC; AY41; Fahey USAAF; H&H (for Aeronca applications); J8; J41toJ47; W41toW45.
Applications: (Brazil) C.A.P. 1 (later I.P.T. 4) Planalto, C.A.P. 5 Carioca. (US) Aeronca Model 9 Arrow [NX39581]; Babcock (later Taubman) LC-11 [NR998W]; Culver LFA-90 Cadet, LAR-90, XPQ-8, PQ-8, TDC-1 Target Drones; Interstate S1A-85F, -90F Cadets; Langley Twin 29-90; Monocoupe 90-AF, L-7A; Piasecki PV-2; Rearwin 190F Skyranger; Sackett J-1 Jeanie; Stinson 10-A, L-9A, L-9B; Stout Skycar II [NX22446].

4cyl; 4ACG-199; 102hp@2500rpm-113@3500; 1941-1945; Wt = 224-256#; TC = 226 in c.1941 - expired 12/5/50.
Geared to 0.63; Military O-200-5 (102@2500).
aerofiles.com (for applications); Ae42toAe43; AMC; AY41; Fahey USAAF; J8; J41toJ45-46; W41toW44.
Applications: (US) Convair (Stinson) Model 103 Spratt Tilt-Wing [NX22448]; Goodyear GA-1 Duck [NX36280]; Interstate S1B-1 Cadet, XL-6, L-6; Piper PA-7 (also PWA-1) Sky Coupe [NX4500].


O-225 -- {4.5 / 3.5 / 222.7} / {114.3 / 88.9 / 3649}

Same bore and stroke as O-110, O-335.
Same stroke as O-120, O-175, O-200, O-235, O-265, O-300, O-315, O-350, O-400, O-595.
4A4 series are the four-cylinder versions of the 2A4 (O-110), 6A4 (O-335) series; Franklin also called this series of engines 4AL-225 for their displacement. The Type Certificate was sold to WSK-PZL in 1975, but engine was not produced subsequently.

4cyl; 4A4-75; 75hp@1950rpm; 1945-1949; Wt = 191-198#; TC = 239 on 9/27/45.
J47toJ52-53; S; W46toW49.
Applications: None found.

4cyl; 4A4-85; 85hp@2200rpm; 1945-1949; Wt = 191-198#; TC = 239 on 9/27/45.
J47toJ52-53; S; W46toW49.
Applications: None found.

4cyl; 4A4-95; 95hp@2450rpm; 1945-1949; Wt = 191-198#; TC = 239 on 9/27/45.
S; W46toW49.
Applications: None found.

4cyl; 4A4-100; 100hp@2550rpm; 1945-1953; Wt = 191-198#; TC = 239 on 9/27/45.
aerofiles.com (for applications); AY51,52; J47toJ52-53; S; W46toW53.
Applications: (Chile) Government Workshops Triciclo-Experimental. (US) Bendix Models 51 [NX34106], 51A [NX40051], 52 [NX34103], 55 [NX34110]; Dansaire Coupe; Eshelman E.F.100 Winglet.

4cyl; 4A-225; 125hp@2800rpm; 1962-1963; Wt = N/A; TC = none.
Relationship to the 4A4 is unknown. It was a four-cylinder engine introduced in 1962 to broaden the product range and was developed into the 4A-235 (O-235) with an increase in bore. See, also, the 2A-110 (O-110) and 6A-335 (O-335).
aerofiles.com (for application); W62-63.
Applications: (US) Cessna 160 [N5419E].


O-235 -- {4.625 / 3.5 / 235.2} / {117.5 / 88.9 / 3854}

Same bore and stroke as O-120, O-350.
Same stroke as O-110, O-175, O-200, O-225, O-265, O-300, O-315, O-335, O-400, O-595.
Developed from 4A-225 (O-225) with an increase in bore. Sold to WSK in 1975 and produced by PZL.

4cyl; 4A-235; 116hp@2800rpm-130hp@2800; 1964-2002; Wt = 223-244#; TC = 6EA on 7/22/64.
Fuel injection or carburetion available.
J64-65toJ75-76 under Franklin; J76-77 to present under WSK-PZL; W66-67toW70.
Applications: (France) Socata MS 884 Rallye-Club (marketed in US as Waco Minerva 125). (Germany) Kaiser Magic aerobatic aircraft. (Poland) PZL-110 Koliber (license-built Socata Rallye). (US) Firewall-Forward Kit for the Skystar Kitfox Models 5, 6, and 7 experimental, homebuilt aircraft series {see the Franklin Aircraft Engines of Colorado Website}.

4cyl; Sport 4; 125hp@2800rpm; 1970; Wt = N/A; TC = none.
Same as 4A-235 but offered to homebuilders in kit form, by which 4 separate packages could be purchased and assembled sequentially; only carburetion available. The TCDS (for TC = 6EA) does not mention the Sport 4 version, but a TC is not necessary for the engine of a homebuilt aircraft.
aerofiles.com (for applications); W70.
Applications: (Canada) Macfam (formerly K&S Aircraft) SA 102.5 Cavalier. (France) Duruble RD-03B Edelweis. (UK) Practavia Sprite prototype. (US) Hollman HA-2M Sportster gyroplane prototype; Stewart JD2FF Foo Fighter [N2123].


O-265 -- {4.0 / 3.5 / 263.9} / {101.6 / 88.9 / 4324}

Same bore and stroke as O-175.
Same stroke as O-110, O-120, O-200, O-225, O-235, O-300, O-315, O-335, O-350, O-400, O-595.

6cyl; 6AC-264; 110hp@2600rpm-120@2600; 1940-1941; Wt = 248-255#; TC = 222 in c.1940 - expired 7/10/45.
AAHSF74 (for 75C); AAHSW93 (for N-1M); aerofiles.com (for applications); Ae41; AY41; J41toJ42; W41.
Applications: (US) Bellanca 14-12-F3 Cruisair; Northrop N-1M "Jeep" [NX28311]; Vultee-Stinson Model 75C [NX27711].

6cyl; 6ACG-264; 138hp@3100rpm; 1940-1941; Wt = N/A; TC = none.
Geared to N/A.
W41.
Applications: None found.


O-300 -- {4.25 / 3.5 / 297.9} / {108.0 / 88.9 / 4882}

Same bore and stroke as O-200, O-400, O-595.
Same stroke as O-110, O-120, O-175, O-225, O-235, O-265, O-315, O-335, O-350.

6cyl; 6AC-298; 130hp@2600rpm-155@2930; 1941-1945; Wt = 260-308#; TC = 225 in c.1944 - expired 12/5/50.
Military O-300-1 was 6AC-298-F3 (125@2675). Steel Products Engineering is also listed as a builder of these engines (AMC).
aerofiles.com (for applications); Ae42toAe43; AMC; AY41; Fahey USAAF; J41toJ42; S; W41toW45.
Applications: (Brazil) C.N.N.A. HL-6. (US) Aeronautical Products A-1 [NX1270], A-3 [NX1272] helicopters; Bell Model 30 helicopter; Bellanca T-14-14 [NX28994]; Fleetwings 33 [NX29033]; Hockaday Comet [NX18993]; Piper P-1 (1941 prototype) [NX38300], PT-1 [NX4300]; Troy (later Cluett) A [NX2619]; Zodiac Libra-Det.

6cyl; 6ACT-298; 150hp@3000rpm ; 1941-1945; Wt = 282-334#; TC = 225 in c.1944 - expired 12/5/50.
Military O-300-3 was 6ACT-298-J4; O-300-11 was 6ACT-298-35 (150@2930). The significance of the "T" in the designation is unknown to the compiler.
Ae42toAe43; AMC; AY41; Fahey USAAF; J41toJ42, J47; S; W41toW45.
Applications: (US) Culver XPQ-9 (canceled), XPQ-10 (canceled), XPQ-14, YPQ-14A, XPQ-15 Target Drones; Erco XPQ-13 Target Drones.

6cyl; 6ACG-298-P5; 160hp@3200rpm; 1941-1945; Wt = N/A; TC = none.
Geared to 0.63; Military O-300-9.
Ae42toAe43; AMC; AY41; Fahey USAAF; J41toJ42, J47; W41toW45.
Applications: (US) Culver PQ-14A, -B, XPQ-14C, TD2C-1 Target Drones.

6cyl; 6ACTS-298; 160hp@3200rpm; 1941-1945; Wt = N/A; TC = none.
Supercharged; the Military O-300-5 was 6ACTS-298-K4; the O-300-7 produced 175@3000. The significance of the "T" in the designation is unknown to the compiler.
Ae42toAe43; AMC; AY41; Fahey USAAF; J41toJ42; S; W41toW45.
Applications: (US) Northwestern XPG-1 (twin-engined conversion of Waco CG-4A glider).

6cyl; 6ACV-298; 160hp@3250rpm; 1944-1946; Wt = N/A; TC = none.
Vertically-mounted and fan-cooled helicopter engine.
W44toW46.
Applications: None found.


Franklin: Part 2 (from O-315)

CONTENTS

Updated 1/20/08