Stability Flashcards
What is static stability
Ability of aircraft to self correct for upsets
The tendency of an aircraft to return to a condition of steady flight by itself after a disturbance
What is dynamic stability
How an aircraft responds over time to a disturbance
The behaviour of the aircraft during the response from the static stability correction
Aircraft may oscilate up and down until it settles down
Define positive static stability
Object returns to its original start position following a disturbance
Define neutral static stability
Object continues to move from its original position without accelerating or decelerating
Define negative static stability
Object continues to diverge (accelerate) from its original start position
Draw and define positive dynamic stability
Aircraft is disturned
Ocilations up and down
Oscilations reduce in size until aircraft returns to normal
Aircraft eventually flying straight and level
See diagram here
Draw and define neutral dynamic stability
Aircraft is disturbed
Ocilations up and down
Ocilations neither increase or decrease
Aircraft continues to oscilate continuously at a steady rate
See diagram here
Draw and define dynamic instability
Aircraft is disturbed
Oscillations up and down
Oscillations grow in size
Aircraft continues to oscillate, growing increasingly unstable
See diagram here
Pitching is achieved around ____ axis?
Lateral
Rolling is achieved around ____ axis?
Longitudinal
Yawing is achieved around ____ axis?
Normal (vertical)
The fin/rudder movement creates ____ and controls the aircraft around ____ axis?
Yaw
Normal (vertical)
The elevator creates ____ and controls the aircraft around ____ axis?
Pitch
Lateral
The aileron creates ____ and controls the aircraft around the ____ axis?
Roll
Longitudinal
In general, CoG is FORWARD or AFT of the CoL?
What effect does this have on the nose pitch tendancy?
Forward
Pitch nose down
Assuming no elevator input
What is the effect of of power on pitch where power is INCREASED
General nose up pitch attitude
Faster airflow occurs over tailplane
Tailplane has more downforce, forcing tail down and nose up
Assuming no elevbator input
What is the effect of power on pitch where power is DECREASED
General nose down pitch attitude
Slower airflow occurs over tailplane
Tailplane has less downforce, tail raises up, pitching nose down
Assuming no elevator input
What is the effect of airspeed on pitch if airspeed is changed
Lift force produced will change
How should a pilot trim to compensate for higher airspeed effects on pitch
TRIM ELEVATOR DOWN
Higher airspeed result in more “lift”
Tailplane “lift” is a downforce
Trimming DOWN reduces the AoA, reducing the lift effect
How should a pilot trim to compensate for lower airspped effects on pitch
TRIM ELEVATOR UP
Lower airspeed results in less “lift”
Tailplane “lift” is a downforce
Trimming UP increases the AoA, increasing the lift effect
If CoG is below the thrust line, which way will the nose pitch when power is applied
DOWN
If CoG is above the thrust line, which way will the nose pitch when power is applied
UP
What angles are Dihedral and Anhedral wing designs
Dihedral
Angled upwards
Positive degree slope from wing base
Anhedral
Angled downwards
Negative degree slope from wing base
How does Dihedral wing design help with stability when aircraft is banked
Lift is perpendicular to wing
Upgoing wing has reduced vertical lift component to downgoing wing
Downgoing wing has more vertical lift vector to support weight of aircraft
Inreases lateral stability
What are the components of the lateral and directional stability couple
Yaw disturbance generates roll moment
Roll disturbance generates yaw moment
What is washout and what effect does it have on AoA
Gradual reduction of AoA from wing root to wing tip
Ensures AoA is smaller at wing tip
Stall occurs at wing root before wing tip
In a stall, how does airflow separation propargate
Starts at the trailing edge on upper surface
Propagates forward towards leading edge
What are stall strips
Attached to leading edge
At high AoA interfer with airflow
Wing behind stall strips stall first
What are vortex generators
Re-energize boundary layer
prolong separation
