The Packard diesel of 1928 was designed to compete with the Wright J-5 "Whirlwind" which powered Lindbergh's "Spirit of St. Louis" in 1927.[32] The specifications were within two percent of each other. The diesel engine's fuel consumption was far less although its price was considerably higher.
_Packard Diesel_ _Wright J-5_ _DR-980_ _"Whirlwind"_
Diameter (in.) 45-11/16 45 Horsepower 225 225 Weight (lb) 510 510 Weight-horsepower ratio 2.26 2.26 Fuel consumption (lb per hp/hr at 0.40 0.60 cruising). Cost $4025 $3000
The advantages of lower fuel cost and greater cruising range offered by the diesel engine would be relatively unimportant to a private pilot flying for pleasure, but would be vital to the commercial operator using airplanes powered by engines having several times the horsepower of the Packard diesel. Its size, moreover, was too small for the technology of fuel injectors.[33] The Packard Company realized that the production engine was too small.[34] In 1930 a 400-hp version was built but was not put into production, probably because of the unreliability of the 225-hp model.
The fourth principal reason why the engine failed is explained by the following quotation from _The Propulsion of Aircraft_, by M. J. B. Davy (published in 1936 by His Majesty's Stationery Office, London):
Although the development and adoption for transport purposes of the relatively high-speed compression ignition engine has been rapid during the last few years, there has been no corresponding advance in its adoption for aircraft propulsion. A reason for this is the recent great advance in "take-off" power in the petrol (gasoline) engine due to the introduction of 87 octane fuel (which permits higher compression ratios) and the strong probability of 100 octane fuels in the near future, still further increasing this power. The need for increased take-off power results from the higher wing loading necessitated by the modern demand for commercial aircraft with higher cruising speeds with reasonable power expenditure.
Production of the Packard diesel ceased in 1933. During that same year the Pratt & Whitney Aircraft Company and the Wright Aeronautical Corporation specified 87-octane fuel for certain of their engines. Less than 10 years later octane ratings had increased to over 100, putting the diesel at a further disadvantage.[35]