01.08 Principles of Operation – Flight Controls


At the end of this lesson, you should be able to correctly:

  • Understand the longitudinal, lateral and vertical axes;
  • Understand roll, pitch, and yaw angles
  • Understand the effects of skid and slip
  • Understand the effect of changes in power on vertical and horizontal speed
  • Understand the relationship between control inputs and aircraft movements
  • Understand the concepts of angle of climb and rate of climb; Understand how trim controls operate

Axes, Planes of Movement & Flight Controls

The three cardinal axes

Skid & Slip

In straight flight, the tail of an aircraft aligns the fuselage into the relative wind. However, in the beginning of a turn, when the ailerons are being applied in order to bank the aircraft , the ailerons also cause an adverse yaw of the aircraft.

For example, if the aircraft is rolling clockwise (from the pilot point of view), the aircraft yaws to the left. It assumes a crab-like attitude relative to the wind. This is called a slip. The air is flowing crosswise over the fuselage.

In order to correct this adverse slip, the pilot must apply rudder (right rudder in this example). If the pilot applies too much rudder, the aircraft will then slip to the other side. This is called a skid.

Side Slip

Power + Attitude = Performance

Power Available Vs Airspeed

Effects of Controls

  • Primary Effects
  • Secondary Effects
  • Further Effects

The Axes

The ‘Normal’ Axes
The ‘Longitudinal’ Axes
The ‘Lateral’ Axes

Angle and Rate of Climb

Climb gradient is the ratio between distance travelled over the ground and altitude gained, and is expressed as a percentage.

The angle of climb can be defined as the angle between a horizontal plane representing the Earth’s surface and the actual flight path followed by the aircraft during its ascent.

Angle of Climb

Best angle of climb (BAOC) airspeed for an airplane is the speed at which the maximum excess thrust is available. Excess thrust is the difference between the total drag of the aircraft, and the thrust output of the powerplant.

Maximum angle of climb is where the aircraft gains the most altitude in a given distance, regardless of the time needed for the maneuver. This is important for clearing an obstacle, and therefore is the speed a pilot uses when executing a “short field” takeoff.

The speed of an aircraft type at which the angle of climb is largest is called Vx.

Rate of Climb

The quickest way for gaining altitude, regardless of the distance covered during such a maneuver, is called best rate of climb and the speed for this is called Vy.

Vx increases with altitude and Vy decreases with altitude until they converge at the airplane’s absolute ceiling.

Trim Controls

Use portion of the control surface to alter airflow over the control and hence reduce or neutralise the force required to hold the control at the given (desired) position.