Lorraine Algol

The Lorraine 9N Algol was a French 9-cylinder radial aeroengine built and used in the 1930s. It was rated at up to 370 kW (500 hp), but more usually in the 220–300 kW (300–400 hp) range.

Type 9-cylinder air-cooled radial aircraft engine
National origin France
Manufacturer Société Lorraine, Argenteuil, Paris
Major applications Bloch 120
Variants Lorraine Sirius

Design and development

The Algol was a conventionally laid out radial engine, with nine cylinders in a single row. The crankcase was a barrel-shaped aluminium alloy casting, with an internal integral diaphragm which held the front crankshaft bearing. Forward of the diaphragm there was an integrally cast cam-gear case for the double track cam-ring. The reduction gear was housed under a domed casing attached to the front of the crankcase.[1]

Flange-mounted steel barrels were bolted to the crankcase and enclosed with cast aluminium alloy, screwed-on, cylinder head with integral cooling fins. The pistons were also made of aluminium alloy and had floating gudgeon pins. The nine pistons drove the single throw crankshaft via one channel-section master rod and eight circular section auxiliary rods. The master rod had an integral, split type big-end. The crankshaft was machined from a single forging, with bolt-on balance weights.[1]

The Algol had a single pair of overhead inlet and exhaust valves per cylinder. The cam-ring drove roller tappets, mounted in the cam-case, which in turn operated rocker arms, fitted with ball bearings, via pushrods. The cam-ring was concentric with the crankshaft and driven via epicyclic gears.[1]

Most Algols were conventionally aspirated via a single carburetter[1] but at least one 1938 variant used a form of fuel injection, where fuel was blown into the induction system rather than the cylinder head.[2]


9N Algol
9Na Algol
9N Algol-Junior
9N Algol-Major
9N Algol-Amelioré
Type 120 500 hp
A developed version with supercharger and reduction gear giving 500 hp (370 kW) at 3,000 m (9,800 ft)[3]



Data from Jane's All the World's Aircraft 1938[1]

General characteristics

  • Type: 9-cylinder single row supercharged radial
  • Bore: 140 mm (5.51 in)
  • Stroke: 150 mm (5.90 in)
  • Displacement: 20.78 L (1,268 cu in)
  • Length: 1.347 m (53.2 in)
  • Diameter: 1.275 m (50.2 in)
  • Dry weight: complete 390 kg (860 lb)


  • Valvetrain: one inlet and one exhaust overhead valve per cylinder, operated with rocker arms, pushrod driven via roller tappets bearing on a double track cam-ring
  • Fuel system: single Stromberg carburettor, heated by exhaust
  • Fuel type: petrol
  • Cooling system: air-cooled
  • Reduction gear: 11:17



  1. Grey, C.G. (1972). Jane's All the World's Aircraft 1938. London: David & Charles. pp. 48d–49d. ISBN 0-7153-5734-4.
  2. "To Paris". Flight. No. 8 December 1938. p. 534.
  3. Société Nationale de Constructions de Moteurs: Argentuil (in French). Argentuil: SNCM. November 1938. Archived from the original on 16 October 2014. Retrieved 11 October 2014.
  4. Parmentier, Bruno. "Sema 12". Aviafrance. Retrieved 14 October 2012.
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