8.4 stability Flashcards
what is maneuverability?
how easily the aircraft and ability to withstand stresses imposed by maneuvers
what is controllability?
ability to respond to pilots control regardless of stability characteristics
the aircraft is free to rotate about what axis?
yaw
pitch
roll
what axis is yaw, pitch, roll on?
yaw is vertical axis
pitch is lateral axis
roll is longitudinal axis
what is a positive yaw?
positive yaw is right
what is the primary control of yaw?
rudder
what is a positive pitch?
nose up
what is the primary control of pitch?
elevators
what is a positive roll?
left wing up
right wing down
what is the primary control of roll what is also the secondary control?
ailerons are primary control
rudder also has effect
what movement, rotation and stability does aileron do?
movement - roll
rotation - longitudinal
stability - lateral
what movement, rotation and stability does elevators/ stabilizers do?
movement - pitch
rotation - lateral
stability - longitudinal
what movement, rotation and stability does rudder do?
movement - yaw
rotation - vertical
stability -directional
what does static stability refer to?
initial tendency of an aircraft to return back to equilibrium
what are the three types of static stability?
positive negative and neutral
what is positive stability?
tendency to return to original state of equilibrium after being disturbed
what is neutral stability?
once disturbed it will remain in its new altitude
what is negative stability?
aircraft will continue to move away from its original altitude once disturbed
what is dynamic stability?
refers to aircraft response over time when given pitch, yaw or bank
what are the three types of dynamic stability?
positive
negative
neutral
what is positive dynamic stability?
has oscillations that dampen over time as it returns to its equilibrium stage
what is neutral dynamic stability?
have oscillations that never dampen out
what is negative dynamic stability?
have oscillations that worsen over time
what is longitudinal stability?
tendency for the nose to pitch up or pitch down around the lateral axis
what does a longitudinal unstable aircraft do?
dive or climb progressively or into a deep dive or stall
what are the three factors of longitudinal stability?
location of the wing with respect to the center of gravity
location of horizontal tail surface with respect to center of gravity
area or size of the tail surface
what is stability?
a body free to rotate always turns about its center of gravity
what does a horizontal stabilizer produce during level flight?
downward force acting with the center of gravity
if the moment arm is balanced between what there will be no change in altitude?
force acting on the horizontal stabilizer and the force from the wings
when does positive longitudinal stability occur?
when the center of gravity as a result of the aircrafts weight is forward of the aerodynamic center
when will the longitudinal stability be high or low?
will be high when the distance between CoG and aerodynamic center is great
will be negative when the distance between CoG and aerodynamic center is small
what is directional stability?
stability around vertical axis
what can improve directional stability?
increase the surface behind the center of gravity by using a dorsal fin
sweep back of a wing
what happens when an aircraft is deflected from its original flight path?
the forward going wing has a larger frontal area to the airflow
what are the 4 factors that make an aircraft latterly stable?
dihedral
sweep back
keel effect
weight distribution
more specifically what is lateral stability determined by?
AOA
dihedral angle
sweep back angle
during level flight the AOA is equal to what?
to the weight
what is the effective AOA?
angle between resultant velocity and the chord line
when there is a gust one one side of the aircraft what will happen?
the wing the gust is on will rise and have a up going velocity and the other wing will have a down going velocity
what do dihedral angles do?
help restore level flight
what creates a resultant force?
lift and weight
what does the resultant force create?
a sideslip
what does a sideslip cause?
flow of air in opposite direction to the relative wind
what stops the slide slip?
difference in lift
what affects lateral stability?
directional stability
what is sideslip?
angle between the aircraft centerline and direction of side slip
what is relative wind opposite to?
sideslip direction
in slide slip what brings the aircraft back to level flight?
difference in lift on wings
what is the keel effect?
type of lateral stability
an aircraft with a positive static stability with a strong keel effect would make what difficult?
to roll left and right
what acts as the keel?
the fuselage as it keeps aircraft pointed in desired direction
what aircraft have a higher keel effect?
high wing aircraft
what is a spiral dive?
exits when there is a grater effect on directional stability on the lateral stability
the rate of divergence in the spiral motion is usually what?
so gradual that the pilot can control it without difficulty
what type of oscillation is Dutch roll?
lateral directional oscillation
what is Dutch roll?
exits when there is a grater effect on lateral stability than directional stability
how can Dutch roll be partially overcome?
by reducing the sweep angle of the wing to improve directional stability
how can directional stability be improved?
by increasing the size of the vertical stabilizer
what can a yaw dampener assist with in terms of Dutch roll?
assist during single engine failure and coordinated turns
what is relaxed stability?
allows the aircraft to be designed for aerodynamic efficiency opposed to handling
stability increases with what?
with speed
to keep an aircraft level what has to be done?
tail has to apply torque to trim out the tendency to pitch down
what system do most modern aircraft use?
fly by wire
