1. FLIGHT CONTROL SYSTEMS
Flying controls are hinged or movable airfoils designed to change the attitude of the aircraft during
flight.
PURPOSE
1. TO ENABLE THE PILOT TO EXERCISE CONTROL OVER THE AIRCRAFT DURING ALL PORTIONS
OF FLIGHT.
2. IT ALLOWS TO MANOEUVRES IN PITCH,ROLL AND YAW.
These can be divided in to 3 groups such as:
(a) PRIMARY CONTROLS
(b) SECONDARY CONTROLS
(c) AUXILARY CONTROLS
PRIMARY FLIGHT CONTROL SRUFACES
Ailerons, Elevators and Rudder are the primary controls. These controls are used to
maneuver the aircraft about its 3 axes.
1. ELEVATOR
2. AILERON
3. RUDDER
2. FLIGHT CONTROL SYSTEMS
SECONDARY FLIGHT CONTROL SYSTEMS:
Flaps, Spoilers, Slats or Leading edge flaps come under this category.
Flaps and slats are the lift augmenting device.
Spoiler again grouped as Ground spoiler and Flight spoiler. Ground spoiler extended only after
the aircraft lands thereby assisting in braking action. The flight spoiler assists in lateral control by
extending whenever aileron on the wing is moved up.
⮚ FLAPS
⮚ SLATS
⮚ SPOILERS
⮚ SPEED BRAKES
AUXILLARY FLIGHT CONTROL SYSTEMS:
Tabs come under this category. Tabs are the small airfoils attached to the trailing edges of
primary control surfaces.
Its purpose is to enable the pilot to trim out any unbalanced condition which may exist during
flight.
3. FLIGHT CONTROL SYSTEMS
COMBINATION FLYING CONTROLS :
STABILATOR:
It combines the function of a horizontal
stabilizer and an elevator. Stabilator normally
equipped with an anti-servo tab, which
doubles as a trim tab. The anti-servo moves in
the same direction that the control surface is
moved to aid the pilot in returning the
stabilator to the trimmed neutral position.
6. • A stabilator vs stabilizer, are both horizontal stabilizers, they look
almost identical and they both control the pitch movement of an
aircraft, however, how they go about doing so is different in one key
way. Horizontal stabilizers, in many aircraft, are fixed and the pitch
movement is controlled by up and down deflection of elevators on the
trailing edge. Stabilators, on the other hand, are fully movable
horizontal stabilizers.
7. • On many modern commercial airliners the horizontal stabilizers are
designed to also move, like a stabilator. There is one key difference,
the movement of a horizontal stabilizer is used for pitch trim. In the
case of a stabilator, trim is usually controlled through elevators and
pitch control is directly input through the yolk or control stick by the
pilot.
8. FLIGHT CONTROL SYSTEMS
COMBINATION FLYING CONTROLS :
RUDDERVATORS:
These flying control surfaces serve the function of the rudder and elevators. The
surfaces are mounted at an angle above horizontal.
When serving as elevators, the surfaces on each side of the tail move in the same
direction, either up or down.
When serving as rudder, the surfaces move in opposite direction, one up and one
down.
When combined rudder and elevator control movements are made, a control-mixing
mechanism moves each surface the appropriate amount to get the desired elevator
and rudder effect.
11. FLIGHT CONTROL SYSTEMS
COMBINATION FLYING CONTROLS :
FLAPERONS:
These are the surfaces combine the operation of flaps and
ailerons.
These types of control surfaces are found on some aircraft
designed to operate from short runways.
The flaperon allows the area of the wing normally reserved for
aileron to be lowered and creates a full span flap.
From the lowered position the flaperon can move up or down to
provide the desired amount of roll control while still contributing
to the overall lift of the wing.
15. FLIGHT CONTROL SYSTEMS
COMBINATION FLYING CONTROLS :
ELEVONS:
Elevons are aircraft control surfaces that combine the functions of the elevator (used
for pitch control) and the aileron (used for roll control).
It is found on Delta wing aircraft. On this type of aircraft the wings are enlarged and
extend to the back of the plane.
There is no separate horizontal stabilizer where you would find the elevators on
conventional straight-wing aircraft.
18. FLIGHT CONTROL SYSTEMS
METHODS:
1. PUSH-PULL CONTROL ROD SYSTEM
2. CABLE AND PULLY SYSTEM
FLIGHT CONTROL SYSTEM COMPONENTS OR COMPONENTS OF
MECHANICAL LIKAGES FLIGHT CONTROL SYSTEM:
1. CABLES
2. PULLEYS
3. TURNBUCKLES
4. PUSH PULL RODS
5. BELL CRANKS
6. QUANDRANTS.
7. TORQUE TUBES
8. CABLE GURARDS
19. FLIGHT CONTROL SYSTEMS
COMPONENTS OF MECHANICAL LINKAGES
1. PUSH PULL ROD:
• Many airplanes and almost all helicopter use push pull rods rather
than control cables for control system.
• Made of heat treated aluminum alloy tubing with threaded ends
riveted to its ends.
• End fittings which have a drilled hole are screwed on to these
threads and to be sure that the rod ends are screwed far enough
in to fitting a safety wire when inserted in to the hole it should not
pass through the fittings.
• A check nut is screwed on to the rod end and when the length of
the push pull rod is adjusted the nut to be screwed up tight
against the end fitting.
• Push pull rods are extensively used along with bell cranks to
change direction and to gain or decrease the mechanical
advantage of control movement.
22. FLIGHT CONTROL SYSTEMS
TORQUE TUBE:
Torque tube is a hollow shaft by which the linear motion of
cable or push pull rod is changed to rotary motion.
A torque arm or horn is attached to the tube by welding or
bolting and imparts motion to the tube as the arm is moved back
and forth.
23. FLIGHT CONTROL SYSTEMS
BELL CRANK:
It is used to transmit force and permit a change in direction of force.
Normally a push pull rod is used with bell crank lever.
24. FLIGHT CONTROL
SYSTEMS
QUADRANT :
• A quadrant serves the same
purpose as a wheel.
• It moves through a small arc
(as much as 100 deg).
• Often employed at the base of
a control column or control stick to
impart force and motion to a
cable system.
FAIRLEADS
• It serves as a guide to prevent
wear and vibration of a cable.
• Made of phenolic material,
fiber, plastic or soft aluminum.
• It is of either split or slotted to
install a cable.
26. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
BLOWN FLAPS:
Systems that blow engine air over the upper surface of the flap at certain
angles to improve lift characteristics.
27. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
KRUEGER FLAP :
It is hinged flap on the leading edge and is often called a "droop."
28. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
PLAIN FLAP: It is attached to the trailing of main plane and rotates on a
simple hinge.
29. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
SPLIT FLAP: It is hinged at the bottom part of the wing near the trailing edge.
The lower surface operates like a plain flap, but the upper surface stays
immobile or moves only slightly.
30. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
FOWLER FLAP: It slides backwards on tracks before hinging downwards,
thereby increasing both camber and chord, creating a larger wing surface
better tuned for lower speeds. It also provides some slot effect. The
Fowler flap was invented by Harlan D. Fowler.
31. FLIGHT CONTROL SYSTEMS
TYPES OF FLAPS:
SLOTTED FLAP: A slot (or gap) between the flap and the wing enables high
pressure air from below the wing to re-energize the boundary layer over
the flap. This helps the airflow to stay attached to the flap, delaying the
stall.
32. FLY BY WIRE CONTROL SYSTEMS
IT IS ONE IN WHICH WIRE CARRYING
ELECTRICAL SIGNALS FROM THE FLIGHT
CONTROLS BY REPLACING MECHANICAL
LINKAGES.
TYPES OR THE WAYS OF USING FBW:
• ANALOG FBW
• DIGITAL FBW
33. FLY BY WIRE CONTROL SYSTEMS
ANALOG FBW:
In analog fly by wire system operation, movements of the control
column and rudder pedals, and the forces exerted by the pilot, are
measured by electrical transducers, and the signals produced are then
amplified and relayed to operate the hydraulic actuator units which are
directly connected to the flight controls surfaces.
The fly by wire control employed in the Boeing 767 (spoiler) as illustrated in
the figure is appended in the next slide:
The main components involved in this system are as follows:
1. POSITION TRANSDUCER (RVDT)
2. SIGNAL CONTROL MODULE
3. LINEAR VARIABLE DIFFERENTIAL TRANSFORMER (LVDT)
4. POWERED FLYING CONTROL UNIT (PFSCU)
35. FLY BY WIRE CONTROL SYSTEMS
DIGITAL FBW:
• A digital FBW system is similar to its analogue counterpart. However
the signaling processing is done by digital computers.
• The pilot can literally say “fly-via-computer”. This increases flexibility
as the digital computers can receive input from any aircraft sensor.
• It also increases stability, because the system is less dependent on
the values of critical electrical components as in analogue controller.
36. FLY BY WIRE CONTROL SYSTEMS
DIFFERENCE BETWEEN ANALOG AND DIGITAL FBW
SL.
NO.
ANALOGUE FBW DIGITAL FBW
01 The FBW eliminates the
complexity, fragility and
weight of the mechanical
circuit of the hydromechanical
flight control systems and
replaces it with an electrical
circuit.
This increases flexibility as the digital
computers can receive input from any
aircraft sensor. It also increases
electronic stability, because the system
is less dependent on the values of
critical electrical components in an
analog controller.
02 The hydraulic circuits are
similar except that mechanical
servo valves are replaced with
electrically-controlled servo
valves, operated by the
electronic controller. This is
the simplest and earliest
configuration of an analog fly-
by-wire flight control system,
The computers "read" position and force
inputs from the pilot's controls and
aircraft sensors. They solve differential
equations to determine the appropriate
command signals that move the flight
controls in order to carry out the
intentions of the pilot.
37. FLY BY WIRE CONTROL SYSTEMS
DIFFERENCE BETWEEN ANALOG AND DIGITAL FBW
SL.
NO.
ANALOGUE FBW DIGITAL FBW
03 In this configuration, the flight
control systems must simulate
"feel". The electronic controller
controls electrical feel devices
that provide the appropriate "feel"
forces on the manual controls.
The programming of the digital
computers enable flight envelope
protection. In this aircraft designers
precisely tailor an aircraft's handling
characteristics, to stay within the
overall limits of what is possible given
the aerodynamics and structure of the
aircraft. Software can also be used to
filter control inputs to avoid pilot-
induced oscillation.
04 In more sophisticated versions,
analog computers replaced the
electronic controller. Analog
computers also allowed some
customization of flight control
characteristics, including relaxed
stability.
Side-sticks, center sticks, or
conventional control yokes can be used
to fly such an aircraft. While the side-
stick offers the advantages of being
lighter, mechanically simpler, and
unobtrusive,
38. FLY BY WIRE CONTROL SYSTEMS
DIFFERENCE BETWEEN ANALOG AND DIGITAL FBW
SL.
NO.
ANALOGUE FBW DIGITAL FBW
05 -----------------------
As the computers continuously "fly" the aircraft,
pilot workload can be reduced. It is now
possible to fly aircraft that have relaxed stability.
The primary benefit for military aircraft is more
manoeuvrable flight performance and so-called
"carefree handling" Digital flight control
systems enable
06 --------------------------
Improves combat survivability because it avoids
hydraulic failure. With a fly-by-wire system,
wires can be more flexibly routed, are easier to
protect and less susceptible to damage than
hydraulic lines.
07 Digital fly-by-wire systems is reliability, even
more so than for analog systems.
39. FLY BY WIRE CONTROL SYSTEMS
ADVANTAGES:
1. WEIGHT SAVING
2. REDUCED MAINTENANCE TIMES
3. LESS SPACE
4. IMPROVED HANDLING
5. Fuel saving:
6. Automatic maneuver envelope protection
7. Gust load alleviation (lessening)
40. ADVANTAGES OF FBW:
1. WEIGHT SAVING
2. REDUCED MAINTENANCE TIMES
3. LESS SPACE
4. IMPROVED HANDLING
41. AUTOPILOT SYSTEM ACTIVE CONTROL TECHNOLOGY:
AUTOPILOT IS A SYSTEM OF AUTOMATIC CONTROLS
WHICH HOLDS THE ARICRAFT
ON ANY SELECTED MAGNETIC HEADING AND
RETURNS THE
AIRCRAFT TO THAT HEADING WHEN IT IS
DISPLACED FROM IT.
PURPOSE:
TO REDUCE THE WROK STRAIN AND FATIQUE OF
CONTROLLING THE AIRCRAFT IN FLIGHT BY THE PILOT.
42. COMPONENTS:
1. GYROS (TO SENSE WHAT
AIRPLANE IS DOING)
2. SERVOS (TO MOVE CONTROL
SURFACES)
3. AMPLIFIER (TO INCREASE THE
STRENGTH OF
GYRO SIGNALS TO OPERATE
SERVOS)
THREE CHANNELS.
1. RUDDER CHANNELS
2. AILERON CHANNES.
3. ELEVATOR CHANNELS
