Page 40 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

Chapter 2: Quadcopter Flight Dynamics 19

Yoke

Throttle

Rudder
Pedals

Figure 2.8 Cessna 172S cockpit.

pulling on the yoke to climb and pushing on it to descend. Throttle changes are often needed
as part of the climb or descent maneuvers. The external, elevator-control surfaces, shown in
Figure 2.7, are the ones involved with climbing and descending.
To make coordinated turns, turn the yoke left or right, and simultaneously press on the
appropriate rudder pedal that matches the turn direction. Using the rudder alone will turn
the aircraft, but it would result in an unpleasant turn in which the aircraft would either slip
or skid throughout the turn. The external, aileron- and rudder-control surfaces, shown in
Figure 2.7, are the ones involved with turning. Turning only the yoke will roll the airplane
around the longitudinal axis without changing its direction of travel. The ailerons are used
solely as the external control surfaces.

Quadcopter Controls
Now that the basic airplane controls have been discussed, we can begin the discussion of the
quadcopter controls. The quadcopter is controlled as if it were a normal R/C guided airplane.
The difference in control happens when the quadcopter’s flight-control board intercepts the
normal flight-control commands and translates them into appropriate motor speed control
signals. That is all that can be controlled on a quadcopter, which lacks the wings, ailerons,
rudder, and flaps found on a normal aircraft. Figure 2.9, taken from the Spektrum DX-8
user’s manual, shows the transmitter I used to control the Elev-8.
The stick on the left controls both the throttle and the rudder, while the stick on the right
controls the ailerons and the elevator. Pushing the left stick forward and back increases or
decreases the motor speed to all motors, respectively. Increasing all motor speeds
simultaneously will send the quadcopter into a vertical flight path that is equivalent to a
climb in a normal aircraft. Obviously, an equal simultaneous reduction in power causes it to
descend. A somewhat more interesting control action happens when the right stick is moved
left or right, a movement that ordinarily controls the elevator of a normal airplane. Changing