Packard 1A-2775 X-24 Engine


Display Status:

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.

Collection Item Summary:

The Packard Motor Car Company 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. Development of the Packard X, basically two Model 1500s sharing one crank-shaft, began about 1920. A few years later, under a Navy contract, Packard built two 1A-2775 engines. The first was test flown for the 1927 Schneider Trophy race by Al Williams in a Kirkham racer, but did not compete. Williams later set an unofficial speed record of 515 kilometers (322 miles) per hour in the racer in 1927.

For the 1929 Schneider Trophy race, Williams modified the racer into a monoplane, which was designated the Mercury Racer. The aircraft was too heavy, so a second, more powerful engine was prepared. Super-charged and rated at 1,119 kW (1,500) horsepower, it was the most powerful aircraft engine in the world. However, the Navy withdrew its support, and the airplane did not race.

Collection Item Long Description:


Circa 1927

Inventory Number


Physical Description

  • Type: Reciprocating, 24 cylinders, X-type, Liquid-cooled
  • Power rating: 969 kW (1,300 hp) at 2,700 rpm
  • Displacement: 45.5 L (2,775 cu in.)
  • Bore and Stroke: 137 mm (5.375 in.) x 140 mm (5.5 in.)
  • Weight: 761 kg (1,677 lb) (Approximate)

Credit Line

Transferred from the U.S. Navy

Country of Origin

United States of America


Aluminum, Steel, Paint, Preservative coating, Textile, Rubber, Copper, Cadmium Plating, Ceramic


  • Other: 45 3/16 x 73 3/16 x 26 13/16 x 55 1/2 x 76 x 36in. (114.8 x 185.9 x 68.1 x 141 x 193 x 91.4cm)
  • Approximate (Weighed with Stand by Cat Forklift): 1043.3kg (2300lb.)
  • Approximate ((without stand)): 760.7kg (1677lb.)

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum


PROPULSION-Reciprocating & Rotary