Flight Controls Flashcards
What are the five major stresses all aircraft are subject to?
- tension
- compression
- torsion
- shear
- bending
Describe Tension
- the stress that resists a force that tends to pull something apart
- tensile strength is measured in psi
- calculate by dividing the load (in pounds) required to pull the material apart by its
cross-sectional area (in sq inches)
Describe Compression
- the stress that resists a crushing force
- the compression strength of material is measured in psi
- it is the stress that tends to shorten or squeeze aircraft parts
Describe Torsion
- the stress that produces twisting
- the torsion strength of a material is its resistance to twisting or torque
Describe Shear
- the stress that resists the force tending to cause one layer of a material to slide
over an adjacent layer - screws, bolts, and rivets are especially subject to shearing force
- the shearing strength of a material is equal to or less than its tensile or
compressive strength
Describe Bending
- a combination of compression and tension
What are Flight Control Surfaces?
- hinged or movable surfaces through which
the attitude of an aircraft is controlled
during takeoff, flight, and landing
What are the two major groups of flight control surfaces?
- Primary or main flight control surfaces
- Secondary or auxiliary control surfaces
What is included in the primary flight control surfaces?
- ailerons
- elevators
- rudder
Describe Ailerons
- ailerons are attached to the trailing edge of
both wings - rotates the aircraft around the longitudinal
axis
Describe the Elevator
- attached to the trailing edge of the horizontal
stabilizer. - it alters aircraft pitch, which is the attitude
about the horizontal or lateral axis
Describe the Rudder
- hinged to the trailing edge of the vertical
stabilizer. - when the rudder changes position, the aircraft
rotates about the vertical axis
Describe some characteristics of primary control surfaces
- usually similar in construction to one another
- vary only in size, shape, and methods of
attachment - must be balanced so they don’t vibrate or
flutter in the wind
Describe primary control surfaces on light aluminum light aircraft
- construction is often similar to an all-metal
wing - typically made from aluminum alloy structure
built around a single spar member or torque
tube to which ribs are fitted and a skin is
attached - ribs are usually stamped out from flat
aluminum sheet stock - holes in ribs lighten
assembly - aluminum skin is attached with rivets
Describe primary flight control surfaces on heavy and high performance aircraft, including gliders, home-built, and light-sport aircraft
- primary control surfaces commonly made
from composite materials - weight and strength advantages over
traditional construction can be significant
Describe the primary control surfaces of a fabric covered aircraft
control surfaces of fabric covered aircraft often have fabric covered surfaces
Describe the primary control surfaces of aluminum skinned aircraft
typically have all aluminum control surfaces
Failure to property balance a control surface could lead to what?
catastrophic failure
Describe Ailerons
- the primary flight control surfaces
- move the aircraft about the longitudinal axis -
movement of ailerons in flight causes plane to
roll - usually located on the outboard trailing edge
of each of the wings - built into the wings and calculated as part of
the wings surface area - controlled by side to side motion of the
control stick in cockpit or rotation of the
control yoke
Where are Ailerons located?
usually located on the outboard trailing edge of each of the wings
How are Ailerons controlled
controlled by side to side motion of the control stick in the cockpit or rotation of the control yoke
When the aileron on one wing deflects down, what happens to the aileron on the opposite wing?
it deflects upward
The pilot’s request for aileron movement and roll are transmitted from the cockpit to the actual control surface in what ways?
system of cables and pulleys, push-pull tubes, hydraulics, electric, or a combination of these
Hydraulic or electric fly-by-wire aileron controls can be found on what type of aircraft?
heavy and high performance aircraft
A second set of ailerons located inboard on the trailing edge of the wings can be found on what type of aircraft?
heavy and high performance aircraft
Why do heavy or high performance aircraft have a second set of ailerons on the trailing edge of the wing?
to provide lateral control and stability in flight
What is an Elevator?
- moves the aircraft around the horizontal or
lateral axis - causes the nose of the aircraft to pitch up or
down - elevator is hinged to the trailing edge of the
horizontal stabilizer - controlled in the cockpit by pushing or pulling
the control stick or yoke forward or aft - light aircraft use a system of control cables
and pulleys or push-pull tubes to transfer info
from the cockpit to the elevator - heavy and high performance aircraft use
hydraulic power to transfer info from the
cockpit to the elevator
Describe the Rudder
- causes an aircraft to yaw or move about the
vertical axis - provides directional control and points the
nose in the direction desired - most aircraft have a single rudder hinged to
the trailing edge of the vertical stabilizer - controlled by a pair of foot operated rudder
pedals in the cockpit
What happens when the right rudder pedal is pushed forward?
it deflects the rudder to the right which moves the nose to the right - the left pedal is rigged to simultaneously move aft
What happens when the left rudder pedal is pushed forward?
the nose of the aircraft moves to the left
Name some dual purpose flight control surfaces
- Elevons - perform combined functions of
ailerons and the elevator - Stabilator - combines the action of both the
horizontal stabilizer and the elevator - Ruddervator - combines the action of the
rudder and elevator(possible on aircraft with V
tail empennages
Describe Flaps
- secondary/auxiliary flight control surface
- found on the inboard trailing edge of wings
- extends the camber of the wing for greater lift
and slower flight. - allows control at low speeds for short field
takeoffs and landings - typically can extend 45-50 degrees
- light aircraft - aluminum skin and structure
flaps - heavy aircraft - aluminum or composite
structures used
Describe Trim Tabs
- secondary/auxiliary flight control surface
- found on the trailing edge of primary flight
surfaces - reduces the force needed to move a primary
control surface
Describe Balance Tabs
- secondary/auxiliary flight control surface
- located on the trailing edge of primary flight
control surfaces - reduces the force needed to move a primary
control surface
Describe Anti-balance tabs
- secondary/auxiliary flight control surface
- located on the trailing edge of primary flight
control surfaces - increases feel and effectiveness of primary
control surface
Describe Servo tabs
- secondary/auxiliary flight control surface
- located on the trailing edge of primary flight
control surfaces - assists or provides the force for moving a
primary flight control
Describe Spoilers
- secondary/auxiliary flight control surface
- located in upper and/or trailing edge of wing
- decreases(spoils) lift. can augment aileron
function
Describe Slats
- secondary/auxiliary flight control surface
- located mid to outboard leading edge of wing
- extends the camber of the wing for greater lift
and slower flight - allows control at low speeds for short field
takeoffs and landings
Describe Slots
- secondary/auxiliary flight control surface
- located outer leading edge of wing, forward of
ailerons - directs air over upper surface of wing during
high angle of attack - lowers stall speed and provides control during
slow flight
Describe Leading edge flap
- secondary/auxiliary flight control surface
- located inboard leading edge of wing
- extends the camber of the wing for greater lift
and slower flight - allows control at low speeds for short field
takeoffs and landings
Describe plain flaps
- form the trailing edge of the wing when the
flap is retracted - plain flap is hinged so the trailing edge can be
lowered - increases wing camber and provides greater lift
Describe a split flap
- housed under the trailing edge of the wing
- a braced flat metal plate hinged at several
places along the leading edge - when deployed, the split flap trailing edge
lowers away from trailing edge of the wing - airflow follows the camber created by the
lowered split flap, increasing lift
Describe Fowler flaps
- when deployed, lower the trailing edge of the
wing and slides aft - increasing the area of the
wing - creates more lift via increased surface area
and wing camber - when stowed, the fowler flap retracts under
the wing trailing edge
Describe Slats
- leading edge device which extends wing
camber - can be operated independently of the flaps -
has own switch in cockpit - gives ability to fly aircraft slower with a
reduced stall speed
List some characteristics of Spoilers
- a device found on the upper surface of many
heavy and high performance aircraft - it is stowed flush to the wings upper surface
- when deployed - it raises up into the
airstream and disrupts the laminar airflow of
the wing - reducing lift - often honeycomb core flat panels
- at lows speeds operates when ailerons
operate to assist in lateral movement and
stability - can also be deployed on both wings to act as
speed brakes
Describe Speed Brakes
- found on the upper surface of the wings of
heavy and high performance aircraft - designed to increase drag and reduce speed
- speed brake control is located in the cockpit
List the different types of flight control tabs
- Trim
- Balance
- Servo
- Anti-balance/Anti-Servo
- Spring
Describe a Trim tab
- moves opposite the control surface
- set by pilot from cockpit - uses independent
linkage - statically balances the aircraft in flight - allows
“hands off” maintenance of flight condition
Describe a Balance tab
- moves opposite the control surface
- moves when pilot moves control surfaces -
coupled to control surface linkage - aids pilot in overcoming the force needed to
move the control surface
Describe a Servo tab
- moves opposite the control surface
- directly linked to flight control input devices
- can be primary or back-up means on control
4 aerodynamically positions control surfaces
that require too much force to move manually
Describe a Anti-balance/Anti-Servo tab
- moves in same direction as control surface
- directly linked to flight control input device
- increases force needed by pilot to change
flight control position / de-sensitizes flight
controls
Describe Spring tabs
- moves opposite of control surface
- located in line of direct linkage to servo tab
- spring assists when control forces become too
high in high speed flight - enables moving control surface when forces
are high - inactive during slow flight
List structures visible on wings that contribute to performance
- Winglets
- Vortex generators
- stall fences
- gap seals
What is a Winglet?
- an obvious vertical upturn of the wing’s tip
resembling a vertical stabilizer - designed to reduce the drag created by wing
tip vortices in flight - usually made from aluminum or composite
materialsW
What is a Vortex generator?
- small airfoil sections usually attached to the
upper surface of a wing - designed to promote positive laminar airflow
over the wing and control surfaces - usually made of aluminum and installed in a
spanwise lines - can also be found on the fuselage and
empennage
What is a stallfence?
- a chordwise barrier on the upper surface of
the wing - used to halt the spanwise flow of air
- reduces tendency for wing to stall in light
aircraft - usually made of aluminum
What is a gap seal?
- used to promote smooth airflow in the gap
areas found between the stationary trailing
edge of a wing or stabilizer and the movable
control surface - made from a variety of materials from
aluminum, impregnated fabric, to foam and
plastic
