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pay $3 per pound of mail for the first 1,000 miles and
30 cents per pound for each additional 100 miles flown.
It should be noted that the Kelly Act was not the first
attempt to provide airmail service to the public. The
United States Post Office had begun flying the mail in
the mid-1920s, using obsolete aircraft left over from
World War I. The brave pilots who flew Curtiss JN-4
and deHavilland DH-4 biplanes lacked any benefits to
help them achieve their mission. Despite the total lack
of navigational aids, dangers of weather, night flying,
mechanical failures and fatigue, these pilots flew routes
stretching from coast-to-coast with surprising success.
Lloyd Stearman and Mac Short anticipated that there
would be demand for airplanes designed specifically
for that mission, and the basic Model C2 airframe was
used to develop the C2M. The C2 airframe was designed
from the beginning to accept more powerful engines
than the ubiquitous and aging Curtiss OX-5, and with
the introduction of Wright Aeronautical Corporation’s
nine-cylinder, 200-horsepower J4 static, air-cooled
radial powerplant in 1926, the C2M would have the
horsepower necessary to haul up to 400-500 pounds
of mail. Early in 1926, before relocating to California,
Lloyd Stearman had gained experience engineering the
Wright radial into the airframe of a modified Travel Air
Model “A” to create the Model BW – the first Travel Air
to feature that powerplant as an option. By the end of
1928 the majority of Travel Air biplanes rolling off the
assembly lines were powered by Wright engines.
The Wright J4 engine originally was developed at the
request of the United States Navy. The admirals wanted
to find an alternate powerplant to the inline piston
engines that were cooled by water. The additional
weight of the large coolant heat exchangers coupled
with the required plumbing of tubing, hoses and
connections, made the engines more expensive to
maintain and operate, not to mention being prone to
leaks and other malfunctions. The Navy was searching
for an air-cooled engine to power its future fleet of
fighters, torpedo and dive bombers.
The J4 was among the first modern military and
commercial engines and helped transform the aviation in
the mid-1920s. In the early 1920s the Wright Aeronautical
Corporation hired engineer George Mead to redesign the
original Lawrence radial into a lightweight, reliable
engine. A minor disadvantage of the J4, however, was the
mounting of two magnetos on the front of the crankcase
where they were exposed to moisture, dirt and other
contaminants on the ground and in flight.
Despite its general reliability and robust design,
the J4’s potential proved limited, and by 1927 it was
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­ KING AIR MAGAZINE MARCH 2019