Primary & secondary controls, balance

Each primary control rotates the aircraft about a different axis. Name the axis by the motion around it.

• All three rotations pivot about the aircraft's centre of gravity.
• Axis names fixed to aircraft and pilot, not horizon.

Mechanism:

• Ailerons (camber):
  • Wheel/stick toward a wing: that wing's aileron up (less camber, less lift); opposite aileron down (more camber, more lift).
  • Low-lift wing drops: rolls toward wheel/stick.
• Elevator:
  • Hinged to horizontal stabilizer trailing edge.
  • Aft column: elevator up, less camber, tail pushed down harder than normal tail-down force, nose rises.
  • Forward column: reverse.
• Rudder:
  • Hinged to vertical stabilizer trailing edge, linked directly to pedals.
  • Left pedal: rudder left, fin cambered, tail pushed right, nose yaws left. Right pedal mirrors.
  • Effectiveness increases with airspeed.
  • On ground, pedals steer a linked nose or tail wheel toward pedal direction.

Secondary controls (not a fourth axis):

• Trim tabs: see trim-technique.
• Flaps: see flaps.
• Spoilers: reduce lift, add drag when raised (PHAK ch.6).
  • One wing only (some aircraft): roll, no adverse yaw.
  • Both wings: steeper descent, no speed gain.

Control balancing:

Trap: roll is about the longitudinal axis (not lateral), pitch the lateral (not longitudinal), yaw the vertical (TP 1102).

Practice