Description
The tumbling circuit can be performed with either forward or backward tumbles. The manoeuvre should exhibit accurate positioning and height control with a consistent rate of tumbling.

Preparation
This should begin with practice of forward or backward flips – the choice is yours. Initial practice should be aimed at producing a series of consistent flips that retain altitude and position. The next step is to develop a relatively slow manoeuvre with well-defined vertical sections. This will involve an increase in overall height, but try to achieve consistent smooth flowing tumbles. Once you have developed a good rhythm of smooth flowing ‘flips’ or ‘tumbles’ it is then time to begin to introduce motion whilst the model is tumbling. Initially, begin to introduce small collective pitch changes to help push/pull the model along in the desired direction. The most effective areas for encouraging horizontal motion are during the two vertical sections of the tumble. During these periods the collective pitch inputs should be prolonged to produce the desired motion. Care should be taken to alternate the positive/negative pitch inputs that must be timed correctly to produce the desired motion. The first attempts at a continuous series of tumbles should be at a low ground speed where the pitch inputs are relatively small and give you the opportunity to experiment with timing these pitch changes. As you gain confidence, the ground speed of the tumbling model may be increased with larger pitch inputs during the vertical sections. In this case, not only will the amount of positive/negative pitch used need to be increased, but the way the pitch is applied will also be somewhat different, requiring more prolonged inputs and relatively rapid changes between positive/negative values. Care should be taken not to allow a ‘runaway’ situation to develop, but aim for a moderate ground speed where motion is fast enough to retain momentum, producing smooth and steady progress in a straight line.

Before attempting the full tumbling circuit, I would suggest flying some slow forward and backward circular circuits, both upright and inverted in the intended direction to get you into ‘circuit mode’ before introducing the tumbles. Your practice of pitch control to produce a steady, rhythmic motion is essential to keep the model moving around the circuit, but in addition, both cyclic and tail rotor inputs will be required to keep the model on a circular path. The cyclic requirements during the circuit consist of a steady elevator input, but with small alternate aileron inputs during the nose up/down sections, coupled with balancing rudder inputs to produce a circular path as the model tumbles.

Possible Problems
These usually centre on controlling the speed around the circuit and difficulties producing an accurate circle. It is important to take time to develop smooth and accurate flips that are slow enough to enable sufficient pitch inputs to be introduced during the vertical sections. This is the key to controlling the overall speed around the circuit. It is important to understand that not only timing of the pitch inputs is critical, but also the amounts used. If the tumble is too fast, you will have problems timing the pitch inputs required to move the model along. Producing an accurate tumbling circle will probably be difficult at first. The alternating aileron and rudder inputs required during each tumble are quite small, but important to guide the model in the circular path. I would recommend attempting only small segments of the circle initially, building up to the full circuit over time.