Armstrong Siddeley radials

Thanks gents

According to Alec Lumsden’s ‘British Piston Aero-Engines’:
GF=Geared Fan and PF=Plain Fan (i.e. not geared). In this case the fan provides positive flow into the carburettor(s). While not a ‘proper’ supercharger, the geared fan provides a moderate supercharge, the plain one (running at crankshaft speed) might be described as ‘normally aspirated’.
On your Lynx drawings, the extra G means the final drive is geared.

GF is geared fan and PF is plain fan (supercharging). The Lynx Major became the Cheetah. Information from British Piston Aero Engines.

John