Stability, trim and the further effects of the controls is taught to gain an understanding of how the aircraft maintains stable flight and how the trim and other controls may be used to affect the vertical, longitudinal and lateral stability. The student must have the confidence in controlling the aircraft at this point, such that they can now explore stability and the further effects of controls, primarily the rudder, and have the skills to practise level flight. They should be introduced to the yaw string indicator, and start using their co-ordination skills to advantage. The outline for this exercise is:
- Instructor coaches student’s attempt at Pre-Takeoff Checks.
- Student does not have hands on controls during launch until after 300 feet.
- Instructor directs the student’s attention to the towplane until just before 300 feet.
- Instructor directs students attention to objects that will help judgement of 300 feet, gets student to call out 300 feet, and then check the altimeter.
- Student’s attention directed to the towplane again. If conditions are not turbulent is allowed to follow through on the controls for the remainder of the aerotow. Instructor’s actions during the aerotow are simply described to the student.
- Instructor coaches lookout, release, and turn. Student performs with instructor following through on controls.
- Instructor coaches student attempt to locate the airfield, making sure that the aircraft is in level flight when doing so. Coach the lookout before turns.
- Instructor demonstrates directional stability with student not on the controls. Picks a point closeto the horizon, yawing the aircraft just enough to easily detect the yaw, then centralizes the rudder and allows the nose to swing back. Student does not practise this to avoid ingraining steering with the rudder.
- Instructor demonstrates pitch stability with student following through on the controls. Starts with the normal gliding attitude and coaches the student to raise the nose slightly. The student is then asked to let go of the control stick and observe what happens.
- Student coached to raise the nose slightly above the normal gliding attitude, and then move the trim lever such that the aircraft can be flown hands free in the new pitch attitude. Airspeed noted after aircraft trimmed.
- Instructor demonstrates the further effects of the rudder with the student not on the controls. Starts with level flight in the normal gliding attitude, keeps the ailerons centralized, yaws the aircraft and gets the student to observe the roll.
- Student practises turns as instructor directs flight to the circuit.
- Instructor takes control with student following through and coaches the downwind checks.
- Instructor takes control from the base leg onward with student not on the controls, and provides simple descriptions of the actions taken during the landing.
Once some firm idea is gained of control and stability we can take the opportunity to play with the controls a bit and see how they interact. From level flight we can get student to apply only the rudder. As with our illustration, the aircraft should yaw and since the forward moving wing will meet the wind at a higher angle of attack than the trailing one the aircraft should start to bank. This is a good time to point out the effect on the yaw string. The student can induce aileron drag in the same way. In both cases these should be done in moderate amounts. As an extension to the exercise, a normal, coordinated turn can be established, and then these controls can be used independently to see the effects. Using only the rudder to correct the yaw will be seen to affect the roll and using only the ailerons will affect the yaw as well. As a caution, at this stage these effects should only be done for short periods to illustrate the problem. The main thrust of the student practice should still be co-ordinated turns. Students should be encouraged to find the trim lever, and make all changes while looking ahead. The proper sequence is to change the attitude while looking at the horizon, re-trim, check the airspeed indicator.