The F3P stands for:
F = Flying model
3 = Radio control
P = Indoor Aerobatic Aircraft
The FAI (Fédération Aéronautique Internationale) class of F3P (or indoor precision aerobatics or indoor pattern) involves complex aerial manoeuvres with a radio controlled model aircraft. All manoeuvres in the aerobatic schedule are judged relative to a point on the ground.
The average F3P model is around 1m long, 1m wingspan, and approximately 40 – 100 grams. Two or one-cell lipos are used for power supply, with top models using counter-rotating coaxial motor systems. They can be made out of any material, but are typically made from Depron or carbon fibre covered in Mylar.
Flights are performed directly in front of the judges and the floor, ceiling and walls of the sports hall defines the manoeuvring area. The recommended dimensions of the hall should be about 40 x 20 metres in length and width and between 8 to 12 metres in height.
Each time the model aircraft crosses the centre line, a particular manoeuvre of an aerobatic schedule has to be performed, involving components such as loops, rolls, lines, stall turns, torque rolls, knife-edges, and combinations of these. At the ends of the manoeuvring area, the model aircraft is required to do turn-around manoeuvres to enable it to reverse its direction of travel.
The competitor’s performance is assessed by a panel of judges who will award marks, independently from each other, between 0 and 10 for each manoeuvre, or figure. Manoeuvres are assigned a difficulty factor (K-factor, which is a multiplier of each manoeuvre) depending on the complexity of the particular manoeuvre. Judging is based on four basic criteria: precision (or geometry), smoothness and gracefulness, positioning (display), and size of manoeuvres. Points are subtracted for various types of defects observed by the judges, the severity of these defects, and the number of times these defects are observed.