AC FLIGHT CONTROLS Flashcards
control the forces of flight and the aircraft’s
direction and attitude
flight control systems
2 Subdivided of flight control systems
primary flight controls
secondary flight controls
basic rotation controls : 3 AXES
Longitudinal axis
Lateral axis
Vertical axis
Longitudinal Axis
controlled by the AILERONS
ROLLING
yoke to the left, right wing??
UP
yoke to the right, left wing??
DOWN
Lateral Axis
controlled by elevators
PITCHING
PUSHING the yoke, airplane’s nose goes??
UP
PULLING the yoke, airplane’s nose goes??
DOWN
Vertical Axis
controlled by the rudder
YAWING
3 Aircraft Flight Control System Design
Mechanically
Hydraulically
Electrically
The control surfaces
are connected directly to the cockpit
controls by a system of cables, rods,
levers and chains.
Mechanically
The control surfaces
are moved by hydraulic power.
Hydraulically
Movement of the cockpit
control sends an electrical signal to
the control surface
Electrically
2 parts hydro-mechanical flight control system
mechanical circuit
hydraulic circuit
The circuit which links
the cockpit controls with the
hydraulic circuits.
mechanical circuit
The circuit which has
hydraulic pumps, reservoirs, filters,
pipes, valves and actuators.
hydraulic circuit
It use computers to process the flight control
inputs made by the pilot or autopilot, and
send corresponding electrical signals to the
flight control surface actuators.
Fly-By-Wire (FBW)
Airbus strategy
hard limits
Boeing strategy
soft limits
3 Terms stability and control
stability
maneuverability
controllability
It is the ability of an aircraft to correct
for conditions that act on it, like turbulence
or flight control inputs.
Stability
It is the characteristic
of an aircraft to be directed along a desired
flightpath and to withstand the stresses
imposed.
Maneuverability
It is the quality of the
response of an aircraft to the pilot’s
commands while maneuvering the aircraft.
Controllability
2 Flight Control Stability
Static Stability
Dynamic Stability
3 kinds of static stability
positive static stability
neutral static stability
negative static stability
It exists when the
disturbed object tends to return to
equilibrium
Positive static stability
It exists when the
disturbed object has neither tendency, but
remains in equilibrium in the direction of
disturbance.
Neutral static stability
It exists when the disturbed object
tends to continue in the direction of
disturbance
Negative static stability, or Static Instability
if you hit turbulence and your
nose pitches up, and then immediately
continues pitching up
Negative static stability, or Static Instability
if you hit turbulence and your nose pitches up 5
degrees, and then immediately after that it
stays at 5 degrees nose up,
Neutral static stability
you hit some turbulence, and the
nose pitches up. Immediately after that
happens, the nose lowers and returns to its
original attitude.
Positive static stability
It is the initial tendency of an
aircraft to return to its original position when
it’s disturbed.
Static stability
It is how an airplane
responds over time to a disturbance.
Dynamic stability
3 kinds of dynamic stability
positive dynamic stability
neutral dynamic stability
negative dynamic stability
Oscillations decrease in amplitude with time
positive dynamic stability
Oscillations are constant in amplitude with
time
Neutral Dynamic Stability
Oscillations increase in amplitude with time
Negative Dynamic Stability
It is the quality that
makes an aircraft stable about its
lateral axis.
Longitudinal stability
It involves the pitching motion as the
aircraft’s nose moves up and down in
flight.
Longitudinal stability
It has tendency to dive or climb progressively
into a very steep dive or climb, or even a
stall and sometimes dangerous to fly.
longitudinally unstable aircraft
3 factors of Static longitudinal stability, or
instability
- Location of the wing with respect to the CG
- Location of the horizontal tail surfaces with respect to the CG
- Area or size of the tail surfaces
Most aircraft are designed so that the
wing’s CL (center of lift) is to the ____________________.
rear of the CG
aircraft’s speed decreases
the speed of the airflow over the wing is
decreased
As the aircraft continues in the nose low attitude and its speed increases,
the downward force on the horizontal
stabilizer is once again increased.
LOW SPEED
PITCH UP
LESSER DOWNWARD TAIL LOAD
HIGH SPEED
PITCH DOWN
GREATER DOWNWARD TAIL LOAD
Stability about the aircraft’s
longitudinal axis, which extends from
the nose of the aircraft to its tail.
lateral stability
Stability around the longitudinal axis
lateral stability
4 main design factors
that make an aircraft laterally stable
dihedral
sweepback
keel effect
weight distribution
It is the upward angle of an aircraft’s
wings with the wing tip higher than
the wing root.
Dihedral
Down going wing = greater angle of
attack = increased lift
Down going wing = greater angle of
attack = increased lift
When disturbed, weight of the aircraft
acts like a pendulum, weight under
the wings, to swing aircraft back into
position
Keel Effect
When one wing is dropped, the
lowered wing produces more lift than
the raised wing and the original
position is restored
Sweepback
Stability around the vertical or normal
axis
Directional Stability
Known as yaw stability
Directional Stability
3 Aerodynamic Forces in Flight Maneuvers
Forces in Turns
Forces in Climb
Forces in Descents
all of your lift is acting vertically, and
no lift is acting horizontally
Forces in Turns
an object at rest
or moving in a straight line remains at
res
Newton’s First Law of Motion, the Law
of Inertia
If you roll into a turn using only
ailerons, your vertical lift decreases
and your horizontal lift increases.
If you roll into a turn using only
ailerons, your Vertical lift DECREASES
and your Horizontal lift INCREASES.
As apply back pressure, it actually
raising the nose and getting a higher
angle of attack during a turn.
As apply back pressure, it actually
RAISING the nose and getting a HIGHER
angle of attack during a turn.
As increase the wing’s angle-of-attack with back pressure, it starts approaching the airplane’s
critical angle-of-attack and risk entering an accelerated stall.
As increase the wing’s angle-of-attack with back pressure, it starts approaching the airplane’s
critical angle-of-attack and risk entering an accelerated stall.
After the flightpath is stabilized on the
upward incline, the angle of attack
and lift again revert to about the level
flight values.
Forces in Climb
If the climb is entered with no change
in power setting, the airspeed
gradually diminishes
If the climb is ENTERED WITH NO CHANGE
in power setting, the AIRSPEED GRADUALLY DIMINISHES.
The total drag is greater than the power, and the
airspeed decreases.
The total drag is GREATER THAN the power, and the airspeed DECREASES.
To descend at the same airspeed as
used in straight-and-level flight, the
power must be reduced as the
descent is entered.
Forces of Descents
They are carefully
designed to provide adequate
responsiveness to control inputs while
allowing a natural feel.
Aircraft control systems
The controls usually feel soft and sluggish, and
the aircraft responds slowly to control
applications.
At low airspeeds
The controls become increasingly firm and
aircraft response is more rapid.
At higher airspeeds
The ailerons are attached
to the __________________ of each wing.
outboard trailing edge
Moving the control wheel, or control
stick, to the right causes the right aileron to
deflect upward and the left aileron to
deflect downward.
Moving the control wheel, or control
stick, to the RIGHT causes the RIGHT AILERON to
DEFLECT UPWARD and the LEFT AILERON to
DEFLECT DOWNWARD.
upward deflection of the right
aileron = decreases the camber =
decreased lift on the right wing
upward deflection of the right
aileron = decreases the camber =
decreased lift on the right wing
downward deflection of the left
aileron = increases the camber =
increased lift on the right wing
downward deflection of the left
aileron = increases the camber =
increased lift on the right wing
produces more drag and becomes more
pronounced at low airspeeds.
Adverse Yaw
the increase in aileron
deflection causes an increase in adverse
yaw.
the increase in aileron
deflection causes an increase in adverse
yaw.
3 Ailerons Designed to Counteract Adverse
Yaw
- Differential ailerons
- Frise-type ailerons
- Coupled ailerons and rudder
It is a type of empennage where
the tail plane (horizontal stabilizer) is
mounted to the top of the fin.
T-tail
they are extremely
sensitive to control inputs and aerodynamic
loads
stabilators pivot
4 Secondary Flight Control Surfaces
Flaps
Leading Devices
Spoilers
Trim Systems
It help your wing adapt to your
current phase of flight.
Flaps
It hinge to the back of the wing,
and they pivot down when you extend
them.
MOST SIMPLE FLAPS
Plain flaps
It is deflected from the
lower surface of the airfoil and produces a
slightly greater increase in lift than the plain
flap.
Split flap
most popular flap on aircraft today
Slotted flap
This flap design not only changes the
camber of the wing, it also increases the
wing area. Instead of rotating down on a
hinge, it slides backwards on tracks.
Fowler Flaps
High-lift devices also can be applied
to the leading edge of the airfoil.
Leading Edge Devices
It is a portion of the leading edge
that moves down and forward when it is
deployed, opening a slot behind it and
increasing the camber of the leading edge.
Slat
It is a adjustable opening
between either the leading edge of an
aileron and the rest of a wing or the leading
edge of a wing and a cap fitting over it.
Slot
4 Types of Leading Edge Devices
Fixed Slots
Leading Edge Cuffs
Movable Slats
Leading Edge Flaps
It direct airflow to the upper
wing surface and delay airflow separation
at higher angles of attack.
Fixed slots
As the AOA increases, the high pressure area moves aft below the lower
surface of the wing, allowing the slats to
move forward.
Movable Slats
This type of leading edge device is frequently used in
conjunction with trailing edge flaps and
can reduce the nose-down pitching
movement produced by the latter.
Leading Edge Flaps
It extends the leading
edge down and forward.
Leading Edge Cuffs
It deployed from the wings to spoil the smooth
airflow, reducing lift and increasing drag.
SPOILERS
They are used to relieve
the pilot of the need to maintain constant
pressure on the flight controls.
Trim systems
The most common installation on
small aircraft that is attached to
the trailing edge of the elevator.
single trim tab
ELEVATOR UP = TRIM TAB DOWN = NOSE UP TRIM
ELEVATOR DOWN = TRIM TAB UP = NOSE DOWN TRIM
Those are attached to the control surface
linkage, so when the control surface is
moved in one direction, it
moves in the opposite direction.
Balance Tabs
It is a small
portion of a flight control surface that
deploys in such a way that it helps to move
the entire flight control surface in the
direction that the pilot wishes it to go
Servo Tab
they move in the same direction as the trailing
edge of the stabilator.
Anti-Servo Tabs
It functions as a trim device to relieve control
pressure and maintain the stabilator in the
desired position.
Anti-Servo Tabs
It linkages pivot the horizontal stabilizer about its rear spar.
Adjustable Stabilizer
This tab is bent in one direction or the
other while on the ground to apply a trim
force to the rudder.
Ground Adjustable Tabs
