The Train 2T, 4T and 6T were all low power piston engines for light aircraft, produced in France. They were inverted, air-cooled in-line engines with the same bore and stroke, differing chiefly in the number of cylinders.
In the 1930s Train introduced a series of air-cooled, inverted in-line piston engines for light aircraft. The T series all used the same cylinders, pistons, connecting rods, valve trains and ignition system, combined into 2 (2T), 4 (4T), and 6 (6T) cylinder units of the same layout. The number of crankshaft bearings (3, 5 or 7) and throws (2, 4 or 6) naturally depended on the number of cylinders, as did the number of cams (4, 8 or 12) on the underhead camshaft. Each cylinder had a swept volume of 0.5 l (30.5 cu in), so the displacements were 1 l (61.0 cu in), 2 l (122.0 cu in) and 3 l (183.1 cu in) and the rated outputs 15 kW (20.1 hp), 30 kW (40.2 hp) and 40 kW (53.6 hp) respectively. The Train 6D was a variant of the 6T with increased bore of 85 mm (3.3 in).