George J. Mead (vice president and technical director, Pratt & Whitney Aircraft Company):
Compared with the present Otto cycle engine, the Diesel powerplant weight, including fuel for a long-distance flight, would apparently be less. It is doubtful whether there would be any saving if the orthodox engine were operated on a more suitable fuel. Inherently the Diesel engine must stand higher pressures and therefore is heavier per horsepower. A partial solution of this difficulty is the two-cycle operation, which seems almost a requirement if the Diesel cycle is to be considered at all for aircraft. For any normal commercial operation in the United States there seems to be little or no improvement to be had from the Diesel. After all, it is not entirely a question of fuel cost but payloads carried for a given horsepower. It seemed at one time as though the Diesel was particularly desirable for Zeppelin work. Now that blau gas has been introduced, which obviates the need of valving precious lifting gas, the Diesel cycle seems much less interesting for this purpose. There may be a reduction in fire hazard and radio interference with the Diesel cycle, but it is doubtful whether it will be used in view of these considerations alone.
C. Fayette Taylor (professor of aeronautical engineering, Massachusetts Institute of Technology): “I believe that the compression ignition engine will continue to remain in the experimental stage during the year 1930. I should expect its first really practical installation to be in lighter-than-air craft.”
P. B. Taylor (acting chief engineer, Wright Aeronautical Corporation): “I believe the compression ignition engine is probably the type which will eventually supersede the present electric ignition units. This development will come slowly and will not be a solid injection engine.”
Henry M. Mullinnix (former chief of powerplant section, Navy Bureau of Aeronautics):
The advantages of compression-ignition, including reduced fire hazard, more efficient cycle, elimination of electrical apparatus and hence of radio interference, elimination of carburetion problems, and other benefits less evident, would seem to outweigh the difficulties encountered in metering and injecting minute quantities of fuel at the proper instant. Although the Diesel engine suffers upon comparison with the Otto cycle engine in flexibility there seems to be a definite field for employment of Diesels and a gradual extension of their use may be predicted.
John H. Geisse (chief engineer, Comet Engine Corporation): “I am firmly convinced that the Diesel engine in the future will not only maintain the advantages of Diesel engines as they are now known, but will also be lighter in pounds per horsepower than the present Otto engines.”
Lt. Cdr. C. G. McCord (U.S. Navy, Naval Aircraft Factory): “The use of compression ignition in due time appears to be assured; but increase in weights above those of present Otto cycle engines, to insure reliability, must be expected.”
L. M. Woolson (aeronautical engineer, Packard Motor Car Company): “There is no question that the compression ignition aircraft engine will in time offer severe competition to the gasoline engine. There are, however, many basic problems to be solved for the solution of which there exists no precedent.”
N. N. Tilley (chief engineer, Kinner Airplane and Motor Corp.):