Piaggio P.X

The Piaggio P.X, or Piaggio Stella P.X, was an Italian nine-cylinder radial aircraft engine produced by Rinaldo Piaggio S.p.A. Based on experience license-producing Gnome et Rhône designs, the engine was used to power a number of aircraft during World War II, including the IMAM Ro.37bis and IMAM Ro.43, used extensively by the Regia Aeronautica and Regia Marina respectively.

Design and development
Piaggio acquired a license from Gnome et Rhône in 1925 for their engines derived from the Bristol Jupiter. The designs proved successful and, using this experience, the company designed a range of related radial engines named "Stella", meaning star. The design was led by the engineer Renzo Spolti. The engines were initially known by their number of cylinders, so the first nine-cylinder model in the range was the P.IX of 1933. However, a progressive number in Roman numerals was used as the design progressed, so the P.IX was followed by the P.X.

The Stella P.X was a nine cylinder version of the P.VII. It retained the same bore and stroke as the original Gnome-Rhône designs, 146 mm and 165 mm respectively, but was substantially more powerful than the comparable 9K. The engine had a two piece aluminium alloy crankcase, steel barrels for the cylinders and aluminium alloy heads. A Piaggio T2-80 updraught carburettor was fitted. The basic version, the R., had reduction gear, while the R.C. was also equipped with a compressor.

The engine powered the Italian aircraft that served during World War II. The IMAM Ro.43 was particularly noteworthy for its performance in the Battles of Cape Spartivento and Cape Matapan.

Variants

 * P.X R.: Normally aspirated and geared.
 * P.X R.C.15: Supercharged and geared, rated at 1500 m.
 * P.X R.C.35: Supercharged and geared, rated at 3500 m.

Applications

 * IMAM Ro.37bis
 * IMAM Ro.43
 * IMAM Ro.44
 * Savoia-Marchetti S.73
 * Savoia-Marchetti S.74
 * Savoia-Marchetti SM.81