Into the Wild Blue Yonder: 1944 Jacobs 7-Cylinder Air Cooled Radial Engine

This exquisite aluminum engine, manufactured in 1944, features steel cylinders with aluminum-alloy cylinder heads. Jacobs Aircraft Engine Company began manufacturing its R-755, a seven-cylinder, air-cooled, radial aircraft engine, in 1933. The engine’s power output ranged between 200 and 350 horsepower.

Incorporated in 1927 as Fischer and Jacobs, one of a number of manufacturers of small radial engines founded during the years immediately after World War I, after moving to Camden. New Jersey (where it was briefly known as the Aircraft Engine Corporation), Jacobs was incorporated in Philadelphia in 1929, to design and produce a seven-cylinder radial aircraft engine with an output of 140 horsepower.

In 1934, Jacobs introduced the L-4 engine, which was rated at 225 horsepower. At the time, it was the most efficient aircraft engine produced in its power class, and was immediately competing with more established models engineered and manufactured by other companies.

The engine was the first in its power class to use forged aluminum pistons, sodium-filled exhaust valves, and a magnesium alloy crankcase. Jacobs became a leader in commercial sales of 200-400 horsepower engines. (Because the engine had a tendency at lower rpm’s to vibrate, it was nicknamed “Shakin’ Jake” and “Shaky Jake.”)

The Jacobs seven-cylinder air-cooled radial engine, the Model L-5 (or R-755 as designated for military purposes), was introduced in 1936. This military version of the engine, the R-755-9, was installed in the Waco PG-3/A, the Cessna AT-17A/B/C, and the Cessna UC-78/A/B/C. Other R-755 engine models powered military aircraft that included the Kellett YG-1 autogiro and Stearman PT-18 primary trainer.

During that time, airplanes powered with Jacobs’ engines operated in 26 countries around the world—powering more four- and five-place cabin airplanes than any other engine in its horsepower class.

In 1939, Jacobs was awarded a U.S. government contract for engines in military training aircraft. In 1940, the Canadian government contracted the company for engines in the twin-engine Avro Anson training plane. Jacobs’ Pottstown, Pennsylvania plant was one of four that supplied 330 horsepower L6-MB (R-755-A military designation) engines for the Canadian-built Avro Anson Mk. II.

As a result of its outstanding production of air-cooled engines, in 1941 the United States War Department contracted Jacobs to produce Pratt & Whitney R-985 and R-1340 engines at a government plant. Production continued until 1945.

In the 1970s, Page Industries of Oklahoma purchased the rights to Jacobs engines and for a few years manufactured limited quantities of R-755s, and the turbocharged R-755S.

A model of the Jacobs R-755 made in 1941 was transferred from the U.S. Air Force Central Museum to the National Air and Space Museum, which periodically lends their engine for museums and touring educational presentations on the history of American aviation.

This striking, perfectly restored historic aviation artifact provides an impressive element to the right living- or workspace.