What is the Free Flight?

Free flight is a classical discipline of aeromodelling. Free flight models flight alone without any human control. Radio control can't be used for an official contest flight, but it is allowed to send a command to end the flight (Radio DT). There are several classes which differ in model's surface area and in kind of motor. The most popular classes are F1A, F1B and F1C. Each year, there is World or European Championships and many contests of World Cup series.

Class F1A - Gliders

Surface area	32 - 34 dm^2
Minimum weight	410 g
Maximum length of launching line loaded by 5 kg	50 m

Class F1B - Model aircraft with extensible motor

Surface area	17 - 19 dm^2
Minimum weight of model aircraft less motor	200 g
Maximum weight of motor lubricated	30 g

Class F1C - Model aircraft with piston motor

Maximum swept volume of motor	2.5 cm^3
Minimum total weight	300 g/cm^3 swept volume of motor
Minimum loading	20 g/dm^2
Maximum duration of motor run	5 seconds from release of model

A Brief Introduction to Class F1A

F1A is a very nice sport class that includes running in open air nature, radio tracking and beautiful model gliders.

The F1A model is towed by flyer on 50 m long tow line. The tow line has to be very strong and stiff, but also thin. The best tow lines are made from Spectra fiber.

The model is equipped by some kind of cicrle tow hook which enables circle tow. Thanks to that, a flyer can make circles on the line. It is very important for seeking thermal. When flyer finds some thermal in the air, he accelerates the model by fast run, and then releases the line. In the moment, when the line is released, a timer begins to control the launch phase. It must to stabilize the model from vertical climb to horizontal glide. This kind of launch is called bunt. All time sequences and servo deflections are stored in the timer.

The timer has stored a flight duration time. After that period, a servo tilts stabilizer, and the model is descending to the ground. Some models are also equipped by digital radio transceiver. In that case, the flyer can send a command to end the flight prematurely.

A competition in class F1A takes usually 7 rounds. The maximal flight time is normally 180 sec. If more fliers make full score, there is a fly-off. It is an additional round with 5 or more minute maximum. The duration of one round is about 1 hour. In fly-off, it is 10 minutes.

Another aspect of free flight class is model tracking in the field. Under strong wind conditions, models can reach up to 3 km long distances. So, it is important to equip the model with some tracking system. The simplest device is an acoustic buzzer which works very good for short distances. The most commonly used system transmits pulses of carrier frequency that can be tracked some radio scanner. This system can be joined to radio transceiver, and then the model has only one antenna.

Models itself must be very strong and stiff to stand extreme load during launch. The whole construction must be invariable under different temperature and humidity conditions. Otherwise, it is not possible to trim the model for optimal flight. There is only one material that complies with these conditions. It is a carbon composite, the material with the best ratio between mass and strength.