Download: Diesel Engine in Aviation: the Clerget 14D and 14F

Presentation of one of the first diesel aviation engines: the Clerget 14D, developed by engine engineer F. Clerget

Brief technical history of an aviation diesel engine; the Clerget 14 (variants D and F) developed in the 1930s with a weight / power ratio greater than 1!


With four years of experience acquired on star 9-cyl (Clerget 9B), and to meet the pressing demand of manufacturers who want powerful aviation engines (more than 300 hp), the Clerget group produces in 1932 the first 14-cyl star, baptized 14 D, developing 300 hp at 1500 rpm for a weight of 467 kg.

The 14 D gave birth in 1934 to the 14 E with 36,7 liters of displacement (140 x 170 mm) providing real power of 400 hp thanks to a high speed of rotation, 1 rpm, obtained by a central roller bearing. This engine, which derives from 800 C by increasing the bore, was offered to the market in 9, after having carried out a series of flight tests on the Potez 1934 of the STAé.

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Unexpectedly, from 1934, the Diesel engines developed by the Clerget team at STAé reached in power that of the best gasoline engines, the “Jupiter” at Gnome et Rhône, in its non-supercharged version1, did not exceed 420 hp and the best 12 cylinders having passed homologation at Lorraine, which develops 450 hp. The first engine powered by aviation diesel on the market in the world, the Packard Diesel, although light, 231 kg, produces only 225 hp. The greedy Jumo 204 at Junkers exceeds 500 hp but it weighs more than 800 kg, and what about the Beardmore Diesel propelling the giant British R 101 airship, with its 525 hp at 900 rpm (!) And its 2 kg!

More: 9B the Clerget, another legendary engine

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