The F4D scale class is for scale free flight rubber powered models of not more than 150 g (including motor) and a maximum wing loading of 15 g/dm².
The judging rules used for the F4D scale class are the BMFA-rules, which are also used in the IIFI and British Indoor Scale Nationals competitions:
F4D Open Scale, Rubber [69 KB]
Rules for all scale classes:
General scale rules [75 KB]
Judges guide [95 KB]