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Forces During Flight

Objective​

To understand the effects of the balance of forces on the airplane in different scenarios, and how turning tendencies impact the control of the airplane.

Motivation​

Helps a student develop an intuitive understanding of the turning forces present when flying so they can better anticipate and compensate for these forces.

Timing​

45 minutes

Format​

Elements​

Turning Tendencies​

  1. Torque reaction of the propeller: torquing the airplane to roll to the left
  2. Propeller slipstream/Spiraling slipstream
  3. Gyroscopic precession
  4. P-factor / Asymmetric Loading
    • With a high AOA, the "bite" of the downward moving blade is greater than the "bite" of the upward moving blade
    • Note this can reverse at low AoA, like in a decent

p-factor propeller

Forces​

  • Forces in straight and level, unaccelerated flight [force vector diagram]
  • Forces in a climb [force vector diagram]
  • Forces in a decent [force vector diagram]
  • Concept: Acceleration towards center of turn
    • "Centrifugal" force as a fictitious force
    • Constantly accelerating towards middle of turn
  • Forces in a turn
    • Lift vector tilts towards center of turn
    • Need more lift to remain level
    • This lift means more load factor
    • For a level turn: Higher bank angle, higher load factor, and thus higher stalling speed
    • Stall speed vs bank angle graph
      • Beyond 50 degrees load factor in a level turn increases at a huge rate
  • Adverse yaw in a turn
    • Downward aileron producing less lift, up aileron producing more
    • Slip vs skid: Too much rate of turn, too little rate of turn

References​