Light Plane Heritage published in EAA Experimenter MARCH 1994
A Line
on In-Line by
Engines
Bob Whittier EAA 1235
T
he term “in-line engine” is encountered so infrequently today that many aviation enthusiasts are unsure of its meaning. It refers to any engine having its cylinders arranged in a row, one behind another. Many ultralight engines fit this description. The four-cylinder engines now common in light cars are the in-line type. Decades ago, many luxury cars had in-line engines that people referred to as being of the “straight-8” type to differentiate them from the vee-8 kind. Until recently, in-line six-cylinder
engines were widely used in cars. From the pioneer days up to the 1930s, in-line engines were widely used in aircraft. At fly-ins we still see Ranger in-line engines on the noses of some Fairchilds, and inline de Havilland Gipsy Majors on Tiger Moth biplanes. In museums we can see World War I in-line engines such as the German Mercedes. While most of these had six cylinders, some had eight. These were massive, rugged, dependable engines and weighed between 600 and 800 or more pounds. Because no other airplanes were
around in 1903 for the Wright brothers to look at and duplicate by “eyeball engineering,” the two were very much on their own. By dint of much study, discussion, and original thinking, they worked out their own rules of aerodynamics in order to figure out a workable size and shape for their Flyer. They calculated that at least eight brake horsepower would be needed to generate enough lift from the Flyer’s thin-airfoiled wings. Finding that no auto or marine engine manufacturer of 1903 could supply a single-cylinder en-
English Cirrus upright in-line engine, top left, powered many light civil aircraft such as the de Havilland Gipsy Moth, top right. High positioning of carburetor led to thick, gravity-feed fuel tank in center section. Engine heat and grease flew back onto occupants. Poor over-the-nose visibility. Lower right, both upright and inverted Cirrus engines were made in the United States under license. Inverted Cirrus in Great Lakes biplane, lower left, made possible a much cleaner installation. Editor’s Note: The Light Plane Heritage series in EAA’s Experimenter magazine often touched on aircraft and concepts related to vintage aircraft and their history. Since many of our members have not had the opportunity to read this series, we plan on publishing those LPH articles that would be of interest to VAA members. Enjoy!—HGF
22 AUGUST 2012
