323 - Block 12

What is Adverse yaw? (Yaw due to roll)

Airplane tends to yaw opposite direction of a turn because of a differential in lift and drag from the ailerons.

→ The up-wing aileron travels downward increasing camber, which increases the amount of lift which also increases induced drag creating a yawing moment in that direction

What is overbanking tendency?

When entering a turn, the outside wing travels faster than the inside wing, it produces more lift than the inside wing, causing the aircraft to overbank

What is load factor?

Ratio of the load supported by the airplane’s wing to the actual weight of the aircraft

→ Increases with AOA, Bank, turbulence, etc

What is limit load factor?

The greatest load factor an airplane can sustain without any risk of permanent deformation, where metal first begins to bend.

What is safety/ultimate load factor?

The load factor that will result in catastrophic failure/damage of components

What is the relationship between static and dynamic stability?

For an aircraft to be dynamically stable it first needs to have positive static stability

→ A statically stable airplane may not always be dynamically stable

What is static stability?

Aircrafts initial response to a disturbance:

• Positive → Returns to equilibrium

• Neutral → Stays at new attitude

• Negative → Continuous beyond the new attitude

What is dynamic stability? (think oscillations)

Aircraft’s response to a disturbance overtime

• Positive → Oscillations decrease overtime

• Neutral → Oscillations remain consistent

• Negative → Oscillations become more extreme

What are the axes of an aircraft?

Lateral: Roll moves about, pitch moves around

Longitudinal: Pitch moves about, roll moves around

Vertical: Yaw moves around and about

What is longitudinal stability?

Stability around the lateral axis and along the longitudinal axis

→ pitch stability

What is lateral stability?

Stability about the longitudinal axis and along the lateral axis

→ Roll stability

What is directional stability?

Only stability about and around the same axis (vertical axis)

→ Yaw tendencies

What is the dihedral effect?

Wing design feature that enhances later stability (Roll stability)

→ wing canted upwards so the down wing in a slip is more perpendicular to the relative wind and generates more lift, creating a rolling restoring moment

What is wing sweep?

• wing more perpendicular to relative wind creates restoring moments after displaced from a roll or yaw

Horizontal stabilizer and it’s relation to stability:

Provides necessary tail down force to counteract aircraft’s natural tendencies to drop the nose

What is a dorsal fin?

Increases lateral and directional stability in a sideslip because it adds more surface area to the vertical stabilizer for wind to deflect off of.

→ increases surface area behind the C.G

What is a Dutch roll?

A combination of rolling and yawing oscillations that normally occur when the dihedral effects of an aircraft are more powerful than the directional stability

→ Dutch roll tendency = positive static stability

What is spiral instability?

Negative static stability tendency, as a result of weak dihedral, negative lateral stability, and positive directional stability

→ results in a slow downward spiral, and can progress to a steep spiral

How does a 60-degree bank correlate to G forces?

60-degree bank = 2G’s and increases drag by 300%

How does speed affect a constant bank turn?

Increases speed

• Rate of turn → Decreases

• Radius of turn → increases

Decrease speed

• Rate of turn → increases

• Radius of turn → decreases

How does bank affect a constant speed turn?

Increase in bank

• Rate of turn → increases

• Radius of turn → decreases

Decrease in bank

• Rate of turn → decreases

• Radius of turn → increases

What does high speed aerodynamics assume?

1. The air is compressible

2. Density is variable

What is the 1 variable that changes the Mach number?

Temperature ONLY

What is a shockwave?

As aircraft velocity approaches 1.0 Mach, particles group and form a disturbance

What is Mach tuck?

Shockwave can create blanketing over control surface, can reduce downwash effectiveness of tail

What is coffin corner?

TAS approaches speed of sound: any decrease in speed/increase in angle of attack can cause a stall, any increase in speed/decrease in angle of attack can result in an overspeed