tutorial 5 flight controls this flight
training tutorial will discuss flight
controls to control an aircraft a pilot
must manipulate the aircraft's control
surfaces to maintain a desired
trajectory or assigned vector learning
how control surfaces affect the attitude
of the aircraft is important for safe
and efficient flight
flight controls are what allow the pilot
to control the forces of flight and the
aircraft's direction and attitude
different flight control systems exist
for different types of aircraft the most
basic control systems are mechanical and
date back to early aircraft they are
used today on sport and small general
aviation aircraft in which the
aerodynamic forces are not excessive
they operate by mechanical connections
between the control stick and the
control surface in this case the control
stick is attached by pulleys to the
elevator
as flight control systems become more
complex mechanical circuits were
developed to reduce the weight and
limitations of mechanical systems the
control stick is used to move control
valves on the mechanical circuit which
controls cylinders which move the
control surfaces as technology
progressed even further modern aircraft
are controlled by electric motors
digital computers or fiber optic cables
called fly-by-wire systems this flight
control system replaces the physical
connection between pilot controls and
the flight control surfaces with an
electrical interface
there are two types of flight control
systems primary systems and secondary
systems primary systems consist of
ailerons elevator and rudder secondary
systems consist of wing flaps spoilers
and trim systems the primary control
system changes the pressure of the air
flow around the airfoil these changes in
the air flow allow a pilot to move the
aircraft around its three axes of
rotation the ailerons control role about
the longitudinal axis the ailerons are
located on the outboard trailing edge of
the wings they work opposite to one
another if the pilot moves the control
stick to the right the aileron on the
right side of the plane will move up and
the aileron on the left will move down
this combined motion causes the plane to
roll to the right
adverse yaw is caused when a plane rolls
to the left or right in a roll to the
left as illustrated by the picture the
right aileron moves down to provide more
lift and roll the airplane to the left
during this process the aileron also
produces more drag as a result the plane
yaws toward the raised wing or to the
outside of the bank as seen by the pilot
the pilot must apply rudder pressure to
account for the adverse yaw this effect
is magnified at slower speeds because of
the decreased effectiveness of the
vertical stabilizer and rudder
there are four major systems that are
used to counteract adverse yaw the first
system is coupling the ailerons with the
rudder pictured on the left when the
rudder moves in conjunction with the
ailerons to correct for aileron drag the
second system is differential ailerons
pictured on the right the aileron that
deflects downward does not move as much
as the aileron that deflects up this
helps by increasing drag on the
descending wing thus eliminating most of
the yawing effect
the third system is called the freeze
type ailerons pictured on the left these
ailerons move on an offset pivot which
causes them to be pushed into the air
stream when deflected upward which
causes drag these aliens also have slots
which allow for smoother air flow over
the lowered aileron making it more
effective at high angles of attack the
fourth and last system is called
flaperons pictured on the right
flaperons combined the aspects of the
ailerons and the flaps the pilot can
move the flapper ons like conventional
ailerons or the pilot can lower both
simultaneously like flaps
the elevator controls pitch about the
lateral axis of the airplane the
elevator which is located on the
trailing edge of the horizontal
stabilizer is controlled by pushing the
control stick either forward which
causes the elevator to move down and the
nose to pitch down or back which causes
the elevator to move up and the nose to
pitch up pitching the aircraft happens
about the planes center of gravity
labeled CG on the right
the elevator on this plane is the T tail
type this means the elevator is
positioned high on the vertical
stabilizer so as to remove the
horizontal stabilizer from exhaust blast
and prop wash because it is removed from
prop wash and therefore not receiving
constant airflow the pilot of a t-tail
aircraft must make large control
movement when flying slowly to control
the nodes
a stable later works in much the same
way as an elevator but instead of a
trailing edge control surface the entire
horizontal stabilizer moves up and down
along a pivot point as shown above a
stable a door down spring may be used to
increase nose down pressure if the
center of gravity was placed aft also an
addi servo tab is placed on the back of
the stabilator to decrease the effect of
moving the control surface this
decreases pilot induced over-controlling
the cunard design places a horizontal
stabilizer in the front of the plane
before the main wings the canard
actually produces lift to keep the nose
up which is theoretically more efficient
than using the horizontal stabilizer
surface to lift the nose up which
results in less drag for a given amount
of lift
the rudder controls the aircraft
movement around the vertical axis this
movement is called yah the rudder is
connected to the vertical stabilizer and
is controlled by the rudder pedals in
the aircraft if the left pedal is
depressed then the nose of the aircraft
will yaw to the left
the Beechcraft Bonanza shown above has a
V tail design this design incorporates
rudder vader's which are a combination
of the rudder and the elevator and they
work much like flaperons the pilot is
able to control the rudder and elevator
separately but the control surface acts
as both
secondary flight controls may consist of
wing flaps leading edge devices spoilers
and trim systems flaps are the most
common hi lift devices on an aircraft
they are attached to the trailing edge
of the wing and increase both lift and
drag for any angle of attack there are
four main types of flap plane split
slotted and fowler flaps the plane flap
is the most simple of the flat designs
this design increases the camber of the
wing which causes greater lift but also
greatly increases drag the split flaps
deploy from the lower surface of the
wing and increase lift slightly more
than the plane flap both the plane and
split flap designs cause high drag for a
little lift the slotted flap is the most
popular flap used today the slotted flap
allows high energy air to flow from the
bottom of the wing to the top of the
wing this movement of the air causes a
much greater lift force than either the
plane or split flap the fowler flaps
work much like slotted flaps but they
not only change the wing camber they
also increase the wing surface area they
slide back and down rather than just
down
hi-lift devices may also be added to the
leading edge of the wing the four most
common types are fixed slot movable slot
leading edge flap and leading edge cuff
fixed slots delay air flow separation
until a higher angle of attack this does
not increase the wings camber but still
increases lift the movable slot works in
the same way as fixed slots but either
open when the angle of attack is
increased or by the pilot at any angle
of attack leading-edge flaps work to
increase the camber of the wing and are
commonly used with trailing edge flaps
to reduce the nose down pitching
tendency leading edge cuffs work to
increase the wings camber and lift the
front edge of the wing is pushed down
and forward allowing for more air to
connect with the upper surface of the
wing at higher angles of attack thus
reducing the aircraft stall speed
spoilers helped by reducing lift and
increasing drag over the wing surface
spoilers are used in gliders to
controlled descent and also in large
aircraft to control adverse yaw because
when they are deployed they increase
drag on the lower wing which stops the
plane from yoing to the outside of the
bank also deploying both spoilers at the
same time increases drag and are used to
slow down and reduce ground rule by
transferring weight to the wheels and
thus increasing braking efficiency
trim systems are used to relieve the
pilot of the need to maintain constant
pressure on the flight controls and
usually consists of controls in the
airplane and small hinge devices
attached to the trailing edge of one or
more of the primary flight control
surfaces such as the elevator rudder and
ailerons in small aircraft they are
usually manually controlled by a small
vertically mounted control wheel in
small aircraft the wheel moves the trim
tab on the elevator causing the planes
nose to pitch up or down the pilot
usually establishes a desired power
setting pitch attitude and configuration
and then trims the controls to relieve
the pressure required on the controls
shown above is a balanced tab this tab
automatically moves opposite the control
input to automatically relieve some of
the pressure required to be held by the
pilot the linkage of the flight controls
and the tab is controllable from the
flight deck
anti servo tabs pictured on the left
work in much the same way as balanced
tabs by opposing the force of the pilot
and making the stabilizer less sensitive
ground adjustable tabs as seen on the
right can be adjusted from the ground
and stop the aircraft from skidding left
or right during cruising flight
rather than using a movable tab on the
trailing edge of the elevator some
aircraft have an adjustable stabilizer
this set up connects the stabilizer to a
jack screw and is controlled by either a
trim wheel or crank on a smaller
aircraft and a motor on larger aircraft
auto pilot is an automatic flight
control system that keeps an aircraft in
level flight or on a set course it can
be directed by the pilot or it may be
coupled to a radio navigation signal the
autopilot reduces the physical and
mental workload of a pilot by
controlling the aircraft about one two
or three of its axes during flight a
simple autopilot as shown above might be
able to only keep the nose of the
aircraft in level pitch up or pitch down
flight another autopilot system might
only be able to keep the wings level or
be able to turn to a certain heading
more complex autopilot systems can
control the aircraft about all three
axes and even more advanced auto pilots
will have a feature that allows for
specific vertical speeds or air speeds
the autopilot system works with inertial
navigation systems global positioning
systems gps and flight computers to
control the aircraft to maintain safety
the autopilot incorporates a disconnect
feature to disengage the system
automatically or manually we hope you
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