An explanation of the mechanics of control line and its
advantages compared with other kinds of flying model aircraft. A
control line model aeroplane is one that is tethered by fine
wires or cables (the lines) so that it is forced to fly in a
circle, and fitted with elevators that can be moved by a pilot
holding a control handle attached to the ends of the lines in
the centre of the flying circle. Variations on this theme
providing control by one or three lines also exist, but are
nowhere near as common as the two-line form described here:
Diagram adapted from one in the Aeromodeller Data Book published
by Model & Allied Publications. Aerobatic models are normally
fitted with large wing flaps which move in the opposite
direction from elevators. There are a few ways of achieving
this, some providing a differential action that applies more
flap to the wing nearest the flying circle centre, but a common
arrangement is shown in the following diagram: Diagram from the
Control Line Manual by R.G. Moulton, published