AFTER outlining the history of development of the Packard X engine, the author states the legitimate position in aviation deserved by the water-cooled aviation-engine of this type and predicts large increases in the size, speed and carrying capacity of airplanes within the near future. Passing then to a discussion of the important features of the X-type engine, various illustrations of its parts are commented upon.
The cylinders are built-up from steel forgings, with all welds arranged so as to be subjected to no excessive alternating stresses. The novel features of this cylinder design lie in the fact that the valve seats are entirely surrounded by water and that water space is provided above the combustion-chamber and below the top plate of the cylinder. The cylinder-head is extremely rigid, resisting deflection and assuring the maximum integrity of valve seats. The valve ports are machined integrally with the cylinder-head and are not welded thereto as in the Liberty engine.
The arrangement for obtaining a controlled circulation of exhaust gases around the inlet manifold, a short passage communicating between the exhaust port and the jacket surrounding the inlet manifold, and features of the design of the piston are described. In the former, two small drilled plugs are provided which, under idling conditions, induce a considerable flow of exhaust gases around the inlet manifold and into the mixture, thereby promoting good distribution under idling and throttled operating conditions. The piston design incorporates extremely short skirts, the over-all length of the pistons being 3.164 in. for a diameter of 5.375 in.
Crankcase, crankshaft and other mechanical parts are enumerated. The engine control is illustrated and described. Mention is made of the experimental, acceptance and flight tests, with a brief description of the procedure, and a curve is presented which shows the increase in airplane speed in the last 22 years.
In conclusion, the author advocates governmental aid for airplane development work, since the Government alone possesses the needed skilled specialists and the elaborate testing-equipment required.