In the Spring 2007 Issue of
Curtiss Aviation Engines
An American Success Story
Glenn
H. Curtiss (1878-1930) was one of America’s outstanding aviation pioneers, a
self-taught engineer, and creator of a broad series of commercially successful
engines for both aviation and motorcycles. Best known for his aerial
accomplishments (from the 1908 June Bug to World War I aircraft, such as the
JN-4 “Jenny” trainer), Curtiss developed solid experience with engines long
beforehand (dating back to 1901). His early interest in bicycle racing led to
motorcycling and his motorcycle engines evolved into aero engines—first for
airships, then aeroplanes. Curtiss engines of this era (the most familiar are
his V-8 four-stroke water-cooled designs) were noted for advanced construction
materials, lighter-than-average weight, reasonable reliability and some
innovative mechanical features. Curtiss engines were not the most radical or
advanced examples of the art, but were sufficiently respected and built well
enough to capture the majority of the early U.S. aircraft engine business to the
WWI era and slightly beyond. According to a noted engine historian, Curtiss
produced “the first successful airplane engines marketed in America.”
Aero Engine Drawings by Frank Munger
Liquid-Cooled Engine Status: 1936-1938
While
working at the US National Archives in July 2006, Dave Birch of the Rolls-Royce
Heritage Trust unearthed a document that clearly elucidates both the status of
Allied liquid-cooled engine development and US Army Air Corps plans at the end
of 1936. This memorandum was written by Lt. Col. Oliver P. Echols, Chief of the
Air Corps Engineering Section for Gen. H. H. Arnold, Chief of the Air Corps, in
answer to Gen. Arnold's question, "Have we anything coming out commensurate with
the Rolls-Royce “Merlin” engine?"
It is rare to find a single document that so well summarizes the state of aircraft engine development at a moment in time. However, in hindsight this memorandum painted a rosier picture of the Allison V-1710 than was actually the case and perhaps projects a greater level of optimism than was justified. In fact, Merlin development was ahead of all US liquid-cooled engines and the first to be qualified for use in service aircraft.
A key aspect of Air Corps plans was the reliance on development and wide availability of turbo-superchargers. However, difficulties with development and reliance on materials that became scarce during wartime resulted in most turbochargers going to bombers. Only the Lockheed P-38 and Republic P-47 used turbochargers successfully in a fighter application. Allisons with engine-driven superchargers never caught up with the Merlin until the final year of the war.
The Curtiss AB Aero Engine
An Inspirational Pioneer
On
July 9th, 1915, three of the prototype Hispano-Suiza V-8 engines arrived in
Paris from Barcelona in order to be examined and tested by the French
authorities with a view to producing the engine for the war effort. To say the
engines caused a sensation amongst the military personnel is probably an
understatement. With their monoblock V-8 configuration, enclosed valve gear and
semi-concealed carburettors, the Hispano-Suizas must have looked the epitome of
a compact power unit.
Thus the monoblock aero-engine got off to a very promising start and from then
on there were, broadly speaking, two phases of development. First, everyone
wanted to license-build the Hispano-Suiza and second, everyone wanted to design
a better cast-block motor. In England and the United States, licenses to produce
the Type 34 Hispano-Suiza were granted to the Wolseley Motor Co. and Wright
Aeronautical Corporation. Both concerns got production underway after some
difficulties.
At the Curtiss Aeroplane & Motor Company in the US, the news that Wright Aero
had got the license for the Hispano-Suiza was received with some disquiet. At
the time they had nothing to match it so they embarked on their only real
option, i.e. the “phase two” approach to build a better monoblock engine. Chief
designer, Charles B. Kirkham was told to give it top priority and thus the
Curtiss AB engine came to be.
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