Principles of Flight Leading Cadet Training Stability and

Principles of Flight Leading Cadet Training Stability and Control Lecture 3

Planes & Axes There are 3 AXES that an aircraft rotates on, (all at 90 o to one another) The Longitudinal Axis The Lateral (or Horizontal) Axis and the Normal (or Vertical) Axis All 3 Axes pass through The Centre of Gravity Longitudinal Normal (Vertical) Lateral (Horizontal)

Planes & Axes There are 3 PLANES that an aircraft moves in, (rotating on an axis) The Pitching Plane about its Lateral (Horizontal) Axis (moving the nose up or down) The Rolling Plane about its Longitudinal Axis (moving the wings up or down) The Yawing Plane about its Normal (Vertical) Axis (moving the body left or right) Pitch Yaw Centre of Gravity Longitudinal Roll Normal (Vertical) Lateral (Horizontal)

Planes & Axes The 3 AXES and the 3 PLANES give STABILITY to the aircraft. Axis Plane Stability Lateral Pitching Longitudinal Rolling Lateral Normal Yawing Directional Pitch (Longitudinal) Roll (Lateral) Yaw (Directional) Centre of Gravity Longitudinal Normal (Vertical) Lateral (Horizontal)

The Pitching Plane The tailplane meets airflow at an Angle of Attack of 0° Regardless if the nose pitches UP or DOWN the tailplane will still have an Angle of Attack to the oncoming air. This produces lift which puts the aircraft back into a level flight position. ft Li This means that the tailplane produces Oncoming air in the pitching plane. stability α Oncoming Air Oncoming air α Lif t Tailplane

The Rolling Plane If the wing drops in turbulent air the aircraft begins to slip sideways, and a sidewind strikes it. Because of the angle of the wings they meet the sidewind at an ‘angle of attack’ which is greater on the lower wing than the upper. This produces lift rolling the aircraft until the wings are level. α Sidewind α Lift Slip

The Yawing Plane If an aircraft Yaws to one side by an air disturbance, it continues to ‘crab’ in its original direction, with a sidewind blowing on its fin surfaces. On areas to the rear of the centre of gravity, this sidewind produces a sideways force which, will tend to yaw the aircraft back to its original heading. Large sufficient fin area therefore produces stability in the Yawing Plane. Sidewind Force Centre of Gravity

Stability Aircraft movements such as pitching, rolling and yawing are always described in relation to the pilot. Rolling Pitching Yawing

Control Ailerons Elevators Rudder

Pilot Controls A pilot has 3 main controls to move the aircraft about its 3 axes. Elevators, Ailerons and a Rudder Using these controls the pilot can: Pitch – make the nose rise or fall Roll – make one wing rise and the other fall Yaw – make the nose move left or right Elevators Ailerons Rudder

The Elevators Are hinged to the trailing edge of the tailplane. Moving the control column forwards lowers the elevators, and gives an angle of attack which creates lift, and the aircraft is tail-up, nose–down, pitching about its lateral axis. Lateral Axis Lift Angle of Attack α Moving the stick backwards raises the elevators, creating the opposite effect.

The Ailerons Are hinged to the trailing edge of each wing. Moving the control column to the left raises the LEFT aileron and depresses the RIGHT aileron. The left aileron has a reduced angle of attack and reduced lift The right aileron has an increased angle of attack and increased lift Moving the stick to the right Lift creates the opposite effect, Ailerons therefore control Lift the aircraft in the rolling plane.

The Rudder Is hinged to the trailing edge of the fin. Moving the LEFT rudder pedal forwards moves the rudder to the left, this produces a sideways force to the right. The tail is now pushed to the right and the nose moves to the left. Moving the RIGHT pedal forwards creates the opposite effect. Original The rudder therefore controls the aircraft in the Yawing plane Flight Path New Flight Path Force

Check of Understanding Aircraft movements such as pitching, rolling and yawing are always described in relation to what? The Horizon The Pilot The Ground The Centre of Gravity

Check of Understanding What are three Axes about which an aircraft can move? Longitudinal, Lateral and Pitching Yawing, Rolling and Pitching Longitudinal, Lateral and Normal Pitching, Yawing and Normal

Check of Understanding What sort of movement is shown in the diagram? Diving Yawing Rolling Pitching

Check of Understanding In order to control an aircraft in the pitching plane, the pilot of an aircraft fitted with conventional controls uses? The Tail Fin The Rudder The Ailerons The Elevators

Check of Understanding The movement of an aircraft about its lateral axis is called? Yawing Pitching Rolling Stalling

Check of Understanding Which of these gives an aircraft high directional stability in the Yawing plane? A large fin area A low centre of gravity A small fin area A high centre of gravity

Check of Understanding The movement of an aircraft about its normal axis is called? Pitching Yawing Rolling Damping

Check of Understanding In position 1 the aircraft is climbing vertically. To make the aircraft move to position 2 and then 3, Which way must the pilot move the control column? To the right To the left Backward Forward

Check of Understanding For a particular aircraft, which of these will reduce the stalling speed? A reduction in weight A reduction in power Putting the aircraft into a turn Raising the flaps An Anhedral Angle

Check of Understanding All the axes of rotation of an aircraft pass through? Its centre of pressure A point halfway between the tail and the nose Its centre of gravity A point halfway between a line between the wing tips

Principles of Flight Leading Cadet Training End of Presentation