8.4- Flight Stability and Dynamics Flashcards
What limits the flight paths and altitudes of the aircraft?
Aerodynamic characteristics of the aircraft, propulsion and its structural strength.
What is the vertical axis of movement?
Yaw
What is the lateral axis of movement?
Pitch
What is the longitudinal axis of movement?
Roll
What direction does the nose go in a positive yaw?
To the right.
What is positive pitch?
Raises the nose.
What is the type of stability associated with roll?
Lateral
What is the type of stability associated with pitch?
Longitudinal
What is the type of stability associated with Yaw?
Directional
What is static stability?
Initial tendency of an aircraft to return back to a position of equilibrium.
What are the three types of static stability?
Positive
Negative
Neutral
What is positive static stability?
Return to original state of equilibrium after being disturbed.
What is neutral static stability?
Stay at new attitude when disturbed.
What is negative static stability?
Continues to worsen after being disturbed.
What is dynamic stability?
Aircraft response over time when disturbed from a given position.
What is positive dynamic stability?
Oscillations that dampen out over time and it returns to normal.
What is neutral dynamic stability?
Oscillations that never dampen out.
What is negative dynamic stability?
Oscillations that get worse over time.
What happens to a longitudinally unstable aircraft?
Tend to dive or climb progressively
What is the result of the distance between CoG and aerodynamic centre being far away?
Longitudinal stability is high.
What happens when a gust hits the lower front part of the nose?
Nose up rotation.
When does positive longitudinal stability occur?
When the centre of gravity as the result of all aircraft weights is forward of the aerodynamic centre.
What is directional stability ‘wethercock’?
Stability around the vertical axis.
What happens in directional stability if the turning moment behind the centre of gravity is greater than in front?
The aircraft turns back to its original flight path.
What design do some aircraft have aft of the centre of gravity to improve directional stability?
Increased surface area.
What methods are there of increasing the surface aircraft aft of the centre of gravity?
Dorsal fin or keel surface.
What else helps improve directional stability?
Sweep back of the wing.
Which wing always produces more lift?
Forward going wing.
What is lateral stability?
Stabilize the rolling effect.
What four design effects give lateral stability?
Dihedral
Sweepback
Keel effect
Weight distribution
What is the effective angle of attack?
The angle between the resultant velocity and the chord line.
What do dihedral angles do?
Restore level flight.
What is always at right angles to the lateral axis?
Lift
In disturbed flight the lift is inclined in the direction of?
The lower wing.
What is slideslip?
The aircraft glides to one side without changing flight direction.
What is sideslip opposite too?
Relative wind.
What is keel effect?
Type of lateral stability.
What would strong keel effect result in?
Difficult to roll left and right.
What part of the aircraft acts as a keel?
Fuselage.
Which wing has greater keel effect, high or low?
High wing.
What happens if an aircraft is designed with more stability in one direction more than the other?
Spiral dive or dutch roll.
When does spiral dive exist?
When there is a greater effect on the directional stability than the lateral.
What is dutch roll?
Lateral directional oscillation
When does dutch roll occur?
Greater effect on lateral stability than on the directional stability.
How is dutch roll partially overcome?
Reducing the sweep angle and improving the directional stability.
How can dutch roll be anticipated and supressed?
Yaw dampening system.
What is used to sense the degree of yaw and rate?
Rate gyro.
What else can a yaw damper system assist with?
Single engine failure and coordinated turns.
What systems are considered passive stability control?
Dihedral
Swept wing
Large vertical stabs
Keel surfaces
THS
What is relaxed stability?
Systems that have opposing features that give neutral or negative stability.
What does relaxed stability allow?
The aircraft to be designed purely for aerodynamic efficiency.
What changed the equation of using active flight control systems?
Auto flight controls and fly-by-wire systems.
