Originating from the motorcycle and automobile industry, in 1935 Alvis started its aviation activity, within the motorization field.

-The factories were located in Coventry.

-Their engines' names came from the Greek mythology, so the first engine that was built under license from Gnôme et LeRhône was the "K", a 14-cylinder two-row radial giving 1,100 hp, known as "Pelides" and it was followed by the "Pelides Major". They also built the 14 N.

"Alvis Logo"

-In 1938, Alvis started preparations to build the 18-cylinder, two-row radial "Alcides" 1, but it did not go into mass production.

-Each model was slightly supercharged but both "Major" versions were already supercharged. They used epicyclic gearing.

-The “Maeonides” (sometimes “Maleonides” and “Malonides”) was a 14-cylinder, two-row radial engine. Just like the Alcides this engine did not go into mass production either, as there was no market for it. Not even the RAF was interested.

"Alvis Leonides”

-Success came with the development of the medium power "Leonides" 500 series with a small diameter, 9 radial cylinders and 718.6 cu. in. of total displacement.

-In 1936 the first one was tested giving 450 hp. Test flights began in 1938.

"Another view of the Leonides"

-Development continued with several models and continually increasing power: those of the 502, 503, 504, 514, 521, 523, 524 or 531 series. Most of them gave 560 hp. The Leonides Mk73 series consisted of models 125, 126, 127, 128, 130, 138, 172 or 173 , and were well known too.

-Below we can see a Leonides version that is adapted to be installed in a medium power helicopter. It gave 550 hp with a total weight of 796 lbs.

"Leonides for helicopters"

The "Leonides Major" had 14 cylinders in a two row radial. (instead of 18 that could be assumed, being in the line of 9-cylinder Leonides engines).

"Advertisement from 1957, Leonides for helicopters”

"Alvis Leonides Major”

-The power of Leonides Major was around 850 hp. There were also engines that were derived from Mk 151/155 series, the 700, 701, 751, 755, etc.

-Helicopter variants were mainly installed in Sykorsky 51s and Dragonflies.

"Leonides Major for helicopters"

-To complete the Alvis chapter, now we show photographs with a rear view of the "Pelides".

-A 14-cylinder two-row radial engine that gave about 1,050 hp.

"Alvis Pelides, accessory side"

"Alvis Pelides Major with 1000/1050 hp”

-And the 18-cylinder two-row radial "Alcides" giving 1,650 hp at 2,400 rpm.

"Alvis Alcides"

"Alcides with 1650 hp"

-Both engines had their versions Alcides Major and Pelides Major.

From Appendix 6: Leonides radial engine was mainly designed for use in helicopters. As we have seen in the main text, they were mounted inclined and there were cases where they were mounted horizontally.

-Naturally it has also been installed in fixed surface aircraft.

"Leonides plain view"

"Leonides side view"

-The Leonides gave around 550 hp. In aircraft they were used by Percival Princes, among many others.

"Alvis advertisement for helicopters”

“Alvis fairing for cooling”