F3B Soaring

What F3B stands for? F3B is a code according to the Sporting Code of the Federation Aeronautique Internationale (FAI) F = Model Aeroplanes 3 = Radio Controlled B = Sailplanes

F3B is the worldwide recognized class of radio controlled model sailplanes. Since 1979 world championships are held in this class. (A second RC sailplane class is added to the FAI code recently: F3J (thermal duration class with a single task))

The F3B rules.
A F3B contest is a multi-task event which includes three tasks:

A: Duration. Seven minutes (soon 10 min.) thermal flight with precision spot landing.

B: Distance. Four minutes distance flight over 150 meter closed circuit.

C: Speed. Flight over 4x150 meters

The combination of tasks A, B, and C constitutes a round. A minimum of two rounds must be flown.

All three tasks must be flown with the same model. Only the addition of ballast is allowed or an aerodynamic change of the model when applied by remote control, for instance in the form of camber changing flaps. Most current models have a combination of the aileron, camber changing and brake functions spread out over four wing control surfaces. This is possible with modern computer radio controls. Most pilots use separate flap and trim settings for the different tasks.

Every task begins with a launch with an electrical powered winch. At a maximum of 200 meters from the launch point, a turnaround pulley is fixed. The nylon monofilament starting line is thus 400 meters long, running from the winch towards the pulley and back.

Task A: Duration
The task must be completed within nine minutes from the order of the starter which includes the towing time.

One point will be awarded for each full second from the time the model aircraft is free flying to the time the model aircraft comes to rest, up to a maximum of 420 points (i.e. 7 minutes maximum), for each full second of flight within the working time. No points will be awarded for flight times in excess of working time. The free flying of the model aircraft starts when the model aircraft is released from the towline.

Landing bonus points will be awarded in accordance with the distance from the landing spot.

One point will be deducted for each full second flown in excess of 420 seconds (seven minutes).

Points will be deducted when the model flies shorter or longer than the 7 minutes and points will be deducted for every meter the model is farther removed from the landing spot. The maximum score is 420 sec. + 100 landing bonus points. This score, or the best score in the group of pilots flying at the same time is converted to 1000 points. The other pilots get a partial score.

In general it is necessary to find a region of air with thermal lift, or at least to avoid sinking air to manage the 7 minutes. The best pilots manage the time often within 2 seconds and are seldom more than 1 meter from the spot.

Task B: Distance
After the starting signal, the pilot has seven minutes working time to fly as many laps as possible within a four minute flying time. The laps are defined by two parallel planes at 150 meter distance. Each time the models pass the line (called base A and base B) a signal is given to tell the pilot to turn. The 4 minutes flying time starts each time the pilot starts the task when base A is crossed in the direction of base B. The pilot with the most laps in his group gets the 1000 points.

Task C: Speed
The speed task must be completed within four minutes from the order of the starter including towing time. After release of the tow hook, the pilot has one minute to enter the course and start the speed trial. If the one minute period expires, the model must be landed and relaunched within the original working time period.


After the launch the pilot must try to fly a 4 lap distance (4x150meter) in the shortest possible time. The fastest pilot gets the 1000 points. The pattern flown is in general direct from the launch back to the base A line. There is little time to gain extra height in thermal as only one minute is allowed between the release from the winch line and the starting of the task.

Before entering the speed course, the pilot dives the model sailplane to get the initial speed, after the dive into the speed course the glide angle is smoothly leveled out till at the end of the task the model flies almost horizontally with decreasing speed. The speed task can be flown in around 20 seconds, the better pilots fly under 20 seconds.


In this task the timing and efficient use of height are important as well as adapting the wing loading to the atmospheric circumstances. In order to fly not to much distance the model should be rolled to the appropriate bank angle before the base line is crossed. Experienced pilots will make the speed turns even before they get the audio signal from the line judges, they just know they will be over the base line only one or two meters. This task has the biggest luck factor in the F3B contests because the pilots fly one by one and the thermal lift conditions can change rapidly.

Sources:

*FAI sporting code - Class F3B - Thermal Soaring Models. FAI-CIAM

oct2002