The GUIDE TO PRE-1930 AIRCRAFT ENGINES is offered as testimony and a source of reference for the aircraft engines of that "golden age" of aviation. It brings together under one cover the details and important information concerning the great rarity of American aircraft powerplants which contributed to America's tremendous achievements in aviation. Because of the variety of combinations possible between engines and carburetors and propellers, each engine is covered only in its basic-design model. Consequently, performances, and to some extent weights, will vary depending on the combinations employed to realize a particular power requirement The throaty roar, the staccato drumming, the grinding growl, the clatter and popping-all are sounds reminiscent of bygone days in aviation, when the engine was every bit as exciting as the airplane it powered. These sounds of yesteryear, except in a few rare instances where the aircraft and engine are preserved and operated, are merely fond memories. We can't reproduce the sounds but we have reproduced the historical information about these engines and offer it to you in this GUIDE TO PRE-1930 AIRCRAFT ENGINES. Perhaps no finer example of engineering can be found than is exhibited by the aircraft engine. It contains nothing that it does not require, and every single part of it must have a long service life and return the maximum possible output of power for its reliability has always been of greatest importance and the aircraft engine of today can run almost indefinitely. Even in the "golden age" of aviation it had remarkable reliability for transoceanic flights and endurance attempts. The power-to-weight ratio was steadily improved as was the proportionate rate of fuel consumption. The radial engine achieved a tremendously favorable power-to-weight ratio, but at the expense of frontal area. Consequently, cowling had to be provided to streamline and force the cooling, but it eliminated the weight of liquid-cooling systems along with their inherent problems. In their respective developments, the airplane engine and automobile engine each took a different course. The weight of an aircraft engine had to be kept as light as possible, and the engine had to provide a wide range of performance under a wide range of operating conditions. On the other hand, the auto engine was never critical as to weight, and this fact in turn insured a degree of safety. The auto engine operates under far worse conditions than does the aircraft engine, and suffers much abuse at the hands of careless owners and operators, and it still continues to perform with matchless reliability. This is not so with the aircraft engine.