Controls Chapter 6 Lecture 13

Control Pitch- Trim- Yaw & Roll-

Directional Stability The vertical stabilizer (fin) provides directional stability to the airplane in the same way the horizontal stabilizer acts in the longitudinal case. Figure 6-13 p. 171 weathercock stability

Lateral Stability Lateral stability- is the stabilizing motion about the roll axis 1. Dihedral- one of the most effective ways of stabilizing against slide-slipping 2. Vertical tail provides some lateral stability 3. Fuselage Effect

Considerations for lateral 4. Swept Wing-contributor to lateral stability figure 6-16 p. 175 figure 6-17 p. 175

Directional-Lateral Coupling Coupling-the interaction between rotating motion in one plane and rotating motion in another plane Adverse Yaw- Figure 6-18 p. 177

Lateral Dynamic Motion Spiral Divergence- a yaw will continue gradually until recognized & corrected by the pilot uncorrected the airplane could be in a significant turn of yaw instability & gradually increasing turn of decreasing radius or spiral motion. This motion can end up as a spiral dive called a graveyard spiral

Lateral Dynamic Motion Dutch Roll- oscillating movement from side to side The resulting motion is a series of uncoordinated turns alternating in opposite directions. Airplanes with small vertical tails often exhibit significant Dutch roll motion. Increased dihedral will reduce spiral instability, but will increase Dutch roll tendencies.

Anatomy of the Turn The airplane banks through an angle The lift vector is tilted Enough lift must be generated for the vertical component of lift to equal the weight & keep the plane in level flight. Figure 6-20 p. 180 The tilted vector also has a horizontal component of lift Figure 6-21 p. 181

Radius & Rate of Turn When a body is moving in a circular path, it is subject to a centrifugal force This force is equal to its mass times the square of the forward velocity at any point, divided by the radius of the circle The centrifugal force must be equal & opposite to the inward component of the lift, by Newton’s third law Figure 6-22 p. 182

Load Factor & Stall Speed The total lift on the wing in a bank, must be greater than that in level flight. This means that the wing is experiencing a G-force greater than one, in a level turn. Figure 6-23 p. 184 Figure 6-24 p. 185

Power Limits on Turn Performance When the airplane is banked into a turn it requires more power than wing-level condition. Figure 6-25 p. 186

Please take out a sheet of paper Include today’s date & your name Quiz on Chapter 6 Please take out a sheet of paper Include today’s date & your name

Quiz on chapter 6 List and explain three considerations in lateral stability.