e weight and cost of the
engine installation. Finally, the engine was ideal for aerobatics, since
the injectors, unlike carburetors, would work equally well whether right
side up or upside down.

An advantage peculiar to the Packard among aeronautical diesels was its
light weight. The English Beardmore "Tornado III" weighed 6.9 lb/hp, and
the German Junkers SL-1 (FO-4) weighed 3.1 lb/hp, while the Packard
weighed but 2.3 lb/hp. In fairness to the Beardmore, it was the only one
of the three engines designed for airship use, and part of its heaviness
was due to the special requirements of lighter-than-air craft. A
contemporary and comparable American gasoline engine, the Lycoming
R-680, weighed 2.2 lb/hp. To have designed a diesel aircraft engine as
light as a gasoline one was a remarkable achievement.

Disadvantages

There are four main reasons why the Packard diesel was not successful.
First the Packard Motor Car Company put the engine into production a
brief three years after it was created. The only successful airplane
diesel, the German Junkers "Jumo," was in development more than three
times as long (1912-1929). The following tests indicate that the
Packard diesel was not ready for production, and hence was unreliable.

Packard Motor Car Company 50-Hour Test (Feb. 15-18, 1930): This test was
identical to the standard Army 50-hour test which was used for the
granting of the Approved Type Certificate. The engine tested was
numbered 100, and was the first to be made with production tools
(approximately half a dozen engines had been handmade previously). It
had to be stopped three times, twice due to failure of the fuel pump
plunger springs and once due to the loosening of the oil connection
ring. These failures were attributed to manufacturing discrepancies. In
addition, 4 out of a total of 103 valve springs broke.[29]

U.S. Navy 50-Hour Test (Jan. 22, 1931, to March 15, 1931): The engine
used in the Navy test was numbered 120. (Apparently only 20 production
engines had been built during the preceding 12 months; Dorner in a
letter of March 3, 1962, states that the total number of Packard diesels
produced was approximately 25.) The engine had to be stopped three
times, twice due to valve-spring collar failures and once due to a valve
head breaking. Because of these failures this test was not completed.
The following significant quotations have been extracted from the test:
"The engine is not recommended for servi