Packard 3A-2500 Geared Drive, V-12 Engine

Type: Reciprocating, 12 cylinders, V-type, geared drive, liquid-cooled

Power rating: 596.6 kW (800 hp) at 2,000 rpm

Displacement: 41.6 L (2,539.55 cu in.)

Bore and Stroke: 162 mm (6.375 in.) x 165 mm (6.5 in.)

Weight: 646.4 kg (1,425 lb)

The Packard Motor Car Company of Detroit, Michigan produced the world’s first quantity-production 12-cylinder automobile in in 1916, and belief in that engine carried over to aviation in the following year. Particularly beginning with lessons learned with the World War I era Liberty engines, Packard began development of 12-cylinder aircraft engines in 1923 that would better fully meet requirements of the Army and Navy, with a resulting great step forward made in decreasing the weight per horsepower.

The engines in the Packard 2500 series were built in direct drive and geared types. The development of the 3A-2500, like its predecessors the 1A-2500 and 2A-2500, was sponsored by both the Army and the Navy. By 1927, the Model 2500 was the most powerful standard aircraft engine in existence. It powered the Huff-Daland XHB-1 Cyclops, the Martin 3-Purpose Aircraft, Dornier Superwal, and Boeing PB-1. The Packard 3A-2500 was type certificated for commercial use in January 1929.