Liberty L-12
Liberty L-12 aircraft engine
Type Piston aero engine
National origin United States of America
Manufacturer Lincoln, Ford, Packard, Marmon, Buick
Designer Jesse G. Vincent and Elbert J. Hall
First run c. 1917
Number built 20,748
Variants Liberty L-4, Liberty L-6, Liberty L-8

The Liberty L-12 is an American water-cooled 45° V-12 aircraft engine displacing 1,649 cubic inches (27 L) and making 400 hp (300 kW) designed for a high power-to-weight ratio and ease of mass production. It saw wide use in aero applications, and, once marinized, in marine use both in racing and runabout boats.

A single bank 6-cylinder version, the Liberty L-6, and V-8, the Liberty L-8, were derived from the Liberty L-12. It was succeeded by the Packard 1A-2500.


In May 1917, a month after the United States had declared war on Germany, a federal task force known as the Aircraft Production Board summoned two top engine designers, Jesse G. Vincent (of the Packard Motor Car Company) and Elbert J. Hall (of the Hall-Scott Motor Company), to Washington. They were given the task of designing as rapidly as possible an aircraft engine that would rival if not surpass those of Great Britain, France, and Germany. The Board specified that the engine would have a high power-to-weight ratio and be adaptable to mass production.

The Board brought Vincent and Hall together on 29 May 1917 at the Willard Hotel in Washington, where the two were asked to stay until they produced a set of basic drawings. After just five days, Vincent and Hall left the Willard with a completed design for the new engine,[1] which had adopted, almost unchanged, the single overhead camshaft and rocker arm valvetrain design of the later Mercedes D.IIIa engines of 1917–18.

In July 1917, an eight-cylinder prototype assembled by Packard's Detroit plant arrived in Washington for testing, and in August, the 12-cylinder version was tested and approved.


Major Henry H. "Hap" Arnold with the first Liberty V12 engine completed
Liberty engine production
Ford Liberty 12 data plate with firing order

In the fall of 1917, the War Department placed an order for 22,500 Liberty engines, dividing the contract among the automobile and engine manufacturers Buick, Ford, Cadillac, Lincoln, Marmon, and Packard. Hall-Scott in California was considered too small to receive a production order. Manufacturing by multiple factories was facilitated by its modular design.[2]

Ford was asked to supply cylinders for the new engine and rapidly developed an improved technique for cutting and pressing steel, which resulted in cylinder production rising from 151 per day to over 2,000; the company eventually manufactured all 433,826 cylinders produced, as well as 3,950 complete engines.[3] Lincoln constructed a new plant in record time, devoted entirely to Liberty engine production, and assembled 2,000 engines in 12 months. By the time of the Armistice with Germany, the various companies had produced 13,574 Liberty engines, attaining a production rate of 150 engines per day. Production continued after the war, for a total of 20,478 engines built between July 4, 1917, and 1919.[4]

Although it is widely reported otherwise, a few Liberty engines did see action in France as power for the American version of the British Airco DH.4.[5]

Lincoln production

As the United States entered World War I, the Cadillac division of General Motors was asked to produce the new Liberty aircraft engine, but William C. Durant was a pacifist who did not want General Motors or Cadillac facilities to be used for producing war material. This led to Henry Leland leaving Cadillac to form the Lincoln Motor Company to make Liberty engines. He quickly gained a $10,000,000 government contract to build 6,000 engines.[6] Subsequently, the order was increased to 9,000 units, with an option for 8,000 more if the government needed them.[7] (Durant later changed his mind and both Cadillac and Buick produced the engines.[8])

More than 16,000 Liberty engines were produced during the calendar year 1918. To November 11, 1918, more than 14,000 Liberty engines were produced.[9] Lincoln had delivered 6,500 of the 400 hp (300 kW) V-12 overhead camshaft engines when production ceased in January 1919.[10]


Closeup of a Liberty L-12's valvetrain details, almost matching the later Mercedes D.IIIa design

The Liberty engine was a modular design where four or six cylinders could be used in one or two banks, allowing for inline fours, V-8s, inline sixes, or the V-12.

The design was held together by a two-part cast aluminium crankcase. The two pieces formed the upper and lower halves of the completed assembly and were held together with a series of bolts running around the outside perimeter. As was common for the era, the cylinders were separately formed from forged steel tubes with thin metal jackets surrounding them to provide cooling water flow.

A single overhead camshaft for each cylinder bank operated two valves per cylinder, in an almost identical manner to the inline six-cylinder German Mercedes D.III and BMW III engines. Each camshaft was driven by a vertical driveshaft that was placed at the back of each cylinder bank, again identical to the Mercedes and BMW straight-six powerplants. Delco Electronics provided the ignition system and Zenith the carburetor. Dry weight was 844 lb (383 kg).

Fifty-two examples of a six-cylinder version, the Liberty L-6, which very closely resembled the Mercedes and BMW powerplants in overall appearance, were produced but not procured by the Army. A pair of the 52 engines produced were destroyed by William Christmas testing his so-called "Christmas Bullet" fighter.



An inverted Liberty 12-A referred to as the V-1650 was produced up to 1926 by Packard.

The same designation was later applied to the Packard V-1650 Merlin, an engine with nearly identical engine displacement. This was a World War II Packard produced version of the Rolls-Royce Merlin,[11] and is not to be confused with the earlier Liberty-based version.

Allison VG-1410

The Allison VG-1410 was an air-cooled inverted Liberty L-12, with a geared super-charger, Allison epicyclic propeller reduction gear, and bore reduced to 4+58 in (120 mm), giving a lower displacement of 1,411 in3 (23.12 L).[12][13]

Liberty L-6

Main article: Liberty L-6

A 6-cylinder version of the Liberty L-12, nicknamed the "Liberty Six", consisted of a single bank of cylinders, with the resulting engine bearing a strong external resemblance to both the Mercedes D.III and BMW III straight-six German aviation engines of World War I. 825 cubic inches (13.5 L)

Liberty L-8

Main article: Liberty L-8

An 8-cylinder V engine using Liberty cylinders in banks of four at 45°. 1,099.6 cubic inches (18.0 L)

Mikulin M-5
License production (or copies) produced in the USSR.
Nuffield Liberty
World War II Crusader Mk III, powered by Nuffield Liberty

The Nuffield Liberty tank engine was licensed and produced in World War II by the UK car manufacturer Nuffield. It was used in early cruiser tanks, the Crusader, the Cavalier, and finally Centaur tanks. It was a 27 L (1,649 in3) engine with an output of 340 hp (250 kW; 340 PS), which was inadequate for the increasing vehicle weights as the war progressed and also suffered numerous problems with cooling and reliability.[14]

The Nuffield Liberty ran through multiple versions:[15]



Airco DH.4 in flight over France during World War I
Felixstowe F5L

The primary use of the Liberty was in aircraft.

The engine was also used in the RN-1 (Zodiac) blimp.


The White Triplex

Based on aircraft use the engine provided a good power-to-weight ratio. This made it ideal for use in land speed attempt vehicles.

It was selected for two land speed record attempts.

Both attempts set new records. Both crashed during further attempts, resulting in the deaths of the drivers and a newsreel cameraman.


World War I Mark VIII "Liberty" tank

As early as 1917 the Liberty showed good potential for use in tanks as well as aircraft. The Anglo-American, or "Liberty", Mark VIII tank was designed in 1917–18. The American version used an adaptation of the Liberty V-12 engine of 300 hp (220 kW), designed to use cast iron cylinders rather than drawn steel ones. One hundred tanks were manufactured at the Rock Island Arsenal in 1919–20, too late for World War I. They were eventually sold to Canada for training in 1940, except for two that have been preserved.

Inter-war, J. Walter Christie combined aircraft engines with new suspension design, producing a rapid and highly mobile tank. Using Christie's concept, Russian forces selected and copied the Liberty in the BT-2 & BT-5 Soviet interwar tank (at least one reconditioned Liberty was installed in a BT-5)[citation needed]. Demonstration of this tank was witnessed by the British, and Christie's design characteristics were licensed and incorporated into the British A13 design specification.

World War II Centaur tank, the last type to fit the Nuffield Liberty

As World War II loomed, Nuffield, producing British cruiser tanks, licensed and re-engineered the Liberty for use in the A13 (produced as the Cruiser Mk III) and later cruiser tanks, with an output of 340 hp (410 hp from the Mark IV version). In later British tanks it was replaced by the Rolls-Royce Meteor, an engine based on the Rolls-Royce Merlin aero engine, which offered greater engine power (600 hp).

Nuffield Liberty engines were used in British tanks of immediate pre-war and Second World War:


This section needs expansion. You can help by adding to it. (June 2018)
HD-4 hydrofoil at the Alexander Graham Bell National Historic Site

HD-4 or Hydrodome number 4 was an early research hydrofoil watercraft developed by the scientist Alexander Graham Bell. In 1919, it set a world marine speed record of 70.86 miles per hour (114.04 km/h) powered by two 350 hp Liberty L-12s.

World speed record breaker and five-time Gold Cup champion Gar Wood at the helm of triple Liberty L-12-powered Miss America 2, the second of nine Packard V-12 driven Miss Americas and 1921 Harmsworth Trophy winner

Inventor, entrepreneur, and boat racer Gar Wood set a new water speed record of 74.870 miles per hour (120.492 km/h) in 1920 in a new twin Liberty V-12 powered boat called Miss America. In the following twelve years, Wood built nine more Packard V-12 driven Miss Americas and broke the record five times, raising it to 124.860 miles per hour (200.943 km/h). He also won five straight powerboat Gold Cup races between 1917 and 1921, and the prestigious Harmsworth Trophy nine times between 1920 and 1933, at the helm of his Miss Americas.

Many gentlemen's runabouts, Gold Cup, and other race-winners were built with Liberty L-12 engines.


A number of Liberty engines survive in restored operational and static display vehicles. Displays of the engine itself include:

United Kingdom
United States


Data from Janes's All the World's Aircraft 1919[20]

General characteristics



See also

Comparable engines

Related lists



  1. ^ Trout, Steven (2006). Cather Studies Vol. 6: History, Memory, and War. University of Nebraska Press. pp. 275–276. ISBN 978-0-8032-9464-6.
  2. ^ Yenne, Bill (2006). The American Aircraft Factory in World War II. Zenith Imprint. pp. 15–17. ISBN 978-0-7603-2300-7.
  3. ^ O'Callaghan, Timothy J. (2002). The Aviation Legacy of Henry & Edsel Ford. Wayne State University Press. pp. 163–164. ISBN 978-1-928623-01-4.
  4. ^ Anderson, John David (2002). The Airplane: A History of Its Technology. AIAA. p. 157. ISBN 978-1-56347-525-2.
  5. ^ Vincent 1919, p. 400.
  6. ^ Weiss 2003, p. 45.
  7. ^ Leland and Millbrook 1996, p. 189.
  8. ^ Weiss, H. Eugene (2003). Chrysler, Ford, Durant, and Sloan. McFarland. p. 45. ISBN 978-0-7864-1611-0.
  9. ^ Squier, George O. (10 Jan 1919). "Aeronautics In The United States, 1918". Transactions of the American Institute of Electrical Engineers. XXXVIII: 13. doi:10.1109/T-AIEE.1919.4765601. S2CID 51649497. Retrieved 17 September 2015.
  10. ^ Leland and Millbrook 1996, p. 194.
  11. ^ Gunston, Bill (1986). World Encyclopaedia of Aero Engines. Patrick Stephens. p. 106. ISBN 978-0-85059-717-2.
  12. ^ Grey, C.G., ed. (1928). Jane's all the World's Aircraft 1928. London: Sampson Low, Marston & company, ltd. p. 58d.
  13. ^ "Archived copy". Archived from the original on 2016-03-03. Retrieved 2009-11-09.((cite web)): CS1 maint: archived copy as title (link)
  14. ^ Foreman-Peck, James; Sue Bowden; Alan McKinley (1995). The British Motor Industry. Manchester University Press. p. 87. ISBN 978-0-7190-2612-6.
  15. ^ Neal, Robert J. (2009). A technical & operational history of the Liberty engine : tanks, ships and aircraft 1917-1960. North Branch, MN: Specialty Press. ISBN 978-1580071499.
  16. ^ "Liberty V12 Engine". Darwins Aviation Museum. Archived from the original on February 23, 2017. Retrieved January 29, 2017.
  17. ^ "Liberty 12A V-12". New England Air Museum. Archived from the original on April 15, 2013. Retrieved March 30, 2013.
  18. ^ "Cole Palen's Old Rhinebeck Aerodrome - Aircraft Engines - Page 4 - Liberty". Rhinebeck Aerodrome Museum. Archived from the original on March 4, 2016. Retrieved February 22, 2016. Produced in large numbers and used extensively in mail planes following the War, the Liberty was a significant U.S. contribution to aviation. Jesse Vincent of Packard and E.J. Hall of Hall-Scott designed the engine in five days. One month later the first prototype was built and running.
  19. ^ "Carillon Historical Park". Dayton History. Retrieved April 7, 2020.
  20. ^ Grey, C.G. (1969). Jane's All the World's Aircraft 1919 (Facsimile ed.). David & Charles (Publishing) Limited. pp. 1b to 145b. ISBN 978-0-7153-4647-1.