ed 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]

Although the above disadvantages sealed the Packard diesel's fate, there
were other minor reasons for its failure. The Packard diesel had the
highest maximum cylinder pressure (up to 1500 psi at peak rpm) of any
proven contemporary aircraft diesel engine. Leigh M. Griffith, vice
president and general manager, Emsco Aero Engine Company, had this to
say about the Packard diesel's high maximum cylinder pressure in the
September 1930 _S.A.E. Journal_:

The designers considered it necessary to adopt unusual but
admittedly clever expedients to counteract the great torque
irregularity caused by the excessive maximum pressure. The adoption
of the lower pressure of 800 lbs. would have eliminated the
necessity for the pivoted spring-mounted counterweights and the
shock-absorbing rubber propeller-drive.... The use of such high
pressures is in reality the quick and easy way to secure high-speed
operation and can be justified only from this standpoint, although
the resulting increased difficulty in keeping the engine light
enough was a strong offsetting factor.[36]

Insofar as the engine life was concerned it is true that 1,500-psi
peak pressures