Complex sentence: The initial Alvis aero-engines were licence-built Gnome-Rhone radials, with the first Alvis designed and built aero-engine being the 14-cylinder Alvis Pelides radial in 1936.
Split into simpler sentences: The initial Alvis aero-engines were licence-built Gnome-Rhone radials. The first aero-engine designed and built by Alvis was the 14-cylinder Alvis Pelides radial in 1936.