Controls

Introduction

The principle structure of an aircraft consists of:

• Fuselage: main structural unit
• Wings: airfoils to produce lift
• Flight Control Surfaces:
  • Primary: ailerons, elevator, rudders
  • Secondary: movable trim tabs located on the primary flight control surfaces
  • Auxiliary: wing flaps, spoilers, speed brakes and slats

Trim

• Trim refers to employing adjustable aerodynamic devices on the aircraft to adjust forces so the pilot does not have to manually hold pressure on the controls
• This is done either by trim tabs (small movable surfaces on the control surface) or by moving the neutral position of the entire control surface all together
  • Trim tabs are likely to be on the aileron, elevator and rudder
• Trimming is accomplished by deflecting the tab in the direction opposite to that in which the primary control surface must be held
• The force of the airflow striking the tab causes the main control surface to be deflected to a position that corrects the unbalanced condition of the aircraft
• Because the trim tabs use airflow to function, trim is a function of speed. Any change in speed results in the need to re-trim the aircraft
• An aircraft properly trimmed in pitch seeks to return to the original speed before the change due to its stability
• Trimming is a constant task as soon as you change any power setting, airspeed, altitude, or configuration
• Proper trimming decreases pilot workload allowing for attention to be diverted elsewhere, especially important for instrument flying
• In the pattern, if you have trimmed appropriately, you shouldn't have to use back stick at all, which should also prevent you from exceeding approach speed/on-speed

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