Flight Controls Flashcards

1
Q

FLIGHT CONTROLS

A

Primary and Secondary Flight Controls

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2
Q

Primary Flight Controls

A

Ailerons, Elevator, and Rudder

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3
Q

Secondary Flight Controls

A

Wing flaps, leading edge devices, spoilers, and trim systems

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4
Q

Airfoil Nomenclature

A

Airfoil
Chord Line
Chord
Mean Camber Line
Maximum Camber
Thickness/Chord Ratio
Leading Edge Radius

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5
Q

a shape capable of producing lift with
relatively high efficiency.

A

Airfoil

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6
Q

a straight line joining the centers of
curvature of the leading edge and trailing edges of
an airfoil.

A

Chord Line

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7
Q

the distance between the leading edge and
trailing edge measured along the chord line.

A

Chord

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8
Q

a line joining the leading edge
and trailing edge of an airfoil, equidistant from the
upper and lower surfaces.

A

Mean Camber Line

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9
Q

the maximum distance of the
mean camber line from the chord line. Maximum
camber is expressed as a percentage of chord, with
its location as a percentage in tenths of the chord aft
of the leading edge. When the camber line lies above
the chord line, it is said to have a positive camber.
When the camber line is below the chord line, it is
said to have negative camber. A symmetrical airfoil
has no camber because the chord line and camber
line are co-incidental.

A

Maximum Camber

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10
Q

the maximum thickness
or depth of an airfoil section expressed as a
percentage of chord, with its location as a
percentages of the chord aft of the leading edge. The
thickness and thickness distribution of the airfoil
section have a great influence on its airflow
characteristics.

A

Thickness/Chord Ratio

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11
Q

the radius of curvature of
the leading edge. The size of the leading-edge radius
can significantly affect the initial airflow
characteristics of the airfoil section.

A

Leading Edge Radius

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12
Q

also known as relative wind or
free stream flow.

A

Relative Airflow

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13
Q

Relative airflow has three qualities:

A

Direction, Condition, Magnitude

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14
Q

air parallel to, and in the opposite
direction to the flight path of the aircraft, in fact the
path of the CG; the direction in which the aircraft is
pointing is irrelevant.

A

Direction

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15
Q

air close to, but unaffected by the
presence of the aircraft; its pressure, temperature,
and velocity are not affected by the presence of the
aircraft through it.

A

Condition

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16
Q

the magnitude of the relative airflow is
the true airspeed (TAS).

A

Magnitude

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17
Q

If airflow does not possess all three qualities, it is
referred to as ___________.

A

effective airflow

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18
Q

can also be referred
to as aerodynamic incidence. It is the angle formed
between the chord line and the relative airflow. The
angle between the chord line and the effective
airflow is referred to as the effective angle of attack.

A

Angle of Attack (α or alpha)

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19
Q

the angle between the chord
line and the horizontal datum of the aircraft. (This
angle is fixed for the wing, but may be variable for
the tail plane.)

A

Angle of Incidence

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20
Q

the aerodynamic force which acts 90 degrees
to the relative airflow.

A

Lift

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21
Q

the aerodynamic force which acts parallel to
and in the same direction as the relative airflow (or
opposite to the aircraft flight path).

A

Drag

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22
Q

the resultant of all aerodynamic
forces acting on the airfoil section.

A

Total Reaction

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23
Q

the point on the chord
line, through which lift is considered to act.

A

Center of Pressure (CP)

24
Q

For steady flight, the aircraft must be in a state of
_________ and the
controls enable this to be achieved for all possible
configurations and center of gravity (CG) positions.

A

balance (zero moments around the axes)

25
Q

the controls will be required to maneuver
the aircraft around its three axes. What are those?

A

Longitudinal, Lateral, Normal or Vertical Axis

26
Q

The __________ used on
tail-less aircraft gives both pitching and
rolling.

A

elevon (elevator and aileron)

27
Q

The __________ gives both pitching
and yawing.

A

ruddervator (V tail)

28
Q

The _______ or a movable tailplane
combining the dual function of horizontal
stabilizer and elevator in which gives both
longitudinal stability and control.

A

stabilator

29
Q

The moment around an axis is produced by
changing the aerodynamic force on the
appropriate airfoil (wing, tail or fin) and this may
be done by:

A

Changing the camber of the airfoil
Changing the angle of attack (incidence)
Decreasing the aerodynamic force by spoiling the airflow

30
Q

The increased lift on the up-going wing gives
an increase in the induced drag, whereas the
reduced lift on the down going wing gives a
decrease in induced drag. The difference in
drag on the two wings produces a yawing
moment which is opposite to the rolling
moment, that is, a roll to the left produces a
yawing moment to the right. This is known as
_________.

A

adverse yaw

31
Q

Various methods have been adopted to
reduce the adverse yaw, the main ones in use
are:

A

Differential Aileron
Frise Ailerons
Aileron-rudder coupling

32
Q

The aileron linkage causes the up-going aileron to move through a larger angle than the down-going aileron.

This increases the drag on the up aileron, and
reduces it on the down aileron, and so
reduces the difference in drag between the
two wings.

A

Differential Aileron

33
Q

The _______ has an
asymmetric leading edge. The leading edge of
the up-going aileron protrudes below the
lower surface of the wing, causing high drag.
The leading edge of the down-going aileron
remains shrouded and causes less drag.

A

Frise aileron

34
Q

In this system,
the aileron and rudder systems are
interconnected, so that when the ailerons are
deflected the rudder automatically moves to
counter the adverse yaw.

A

Aileron-rudder coupling

35
Q

The ailerons are normally situated at the
wing tip, to give the greatest moment for the
force produced. However, this also means
that they cause the maximum twisting and
bending loads on the wing. This can cause a
loss of effectiveness or even reversal of the
aileron.

To reduce these effects, the ailerons can be
mounted further inboard. Alternatively, two
sets of ailerons may be fitted, one set at the
wing tip for use at low speeds when the
forces involved are low, and one set inboard
for use at high speeds when the forces are
greater and could cause greater structural
distortion.

A

Inboard Ailerons

36
Q

The flaps and the ailerons both occupy part of
the trailing edge of the wing. For good
take-off and landing performance the flaps
need to be as large as possible, and for a good
rate of roll, the ailerons need to be as large as
possible.

Another system is to use the trailing edge
moveable surfaces to perform the operation
of both flaps and ailerons.

A

Flaperons

37
Q

if the space available is limited, and
one solution is to ______ the ailerons
symmetrically to augment the flap area. They
then move differentially from the _____
position to give lateral control.

A

droop ; drooped

38
Q

________ may be used to give lateral control, in
addition to, or instead of ailerons. The _______
consists of part of the upper surface of the
wing which can be raised.

A

Spoilers

39
Q

Raising the spoiler will disturb the ____
over the wing and reduce the lift. To function
as a lateral control, the spoiler is ______ on the
wing which is required to move downwards
and remains in its retracted position on the
other wing.

A

airflow ; raised

40
Q

Advantages of spoilers compared to the aileron

A

There is no adverse yaw.

Wing twisting is reduced.

At transonic speed, its effectiveness is not
reduced by shock induced separation.

It cannot develop flutter.

Spoilers do not occupy the trailing edge

41
Q

The aerodynamic force acting on a control
surface through its center of pressure will
tend to rotate the control around its hinge, in
the direction of the force. The moment will be
the force multiplied by the distance from the
hinge to the center of pressure. This is called
the ___________. The force may be due to
the angle of attack of the airfoil or the
deflection of the control surface. It is assumed
that the total _________ is the sum of the
separate effects of angle of attack and control
surface deflection.

A

hinge moment

42
Q

The aerodynamic force on the control
at a given deflection will depend on
the_____ of the control surface, and the
speed squared.

A

size

43
Q

_________ involves using the
aerodynamic forces on the control surface, to
reduce the hinge moment

A

Aerodynamic balance

44
Q

Aerodynamic balance may be done in several ways, those are?

A

Set back hinge line
Horn Balance
Internal Balance

45
Q

The moment arm of
the control surface force is the distance from
the hinge to the center of pressure on the
control surface. If the hinge is moved back
into the control surface, the arm and the
hinge moment will be reduced. Setting the
hinge back does not reduce the effectiveness
of the control, only the hinge moment of the
force is reduced, not the force itself.

A

Set Back Hinge Line

46
Q

The principle of the
_________ is similar to that of the
set-back hinge, in that part of the
surface is forward of the hinge line,
and forces on this part of the surface
give hinge moments which are in the
opposite direction to the moments on
the main part of the surface. The
overall moment is therefore reduced,
but not the control effectiveness.

A

horn balance

47
Q

This balance works on the same principle as the set-back hinge, but
the balancing chamber area is inside the rear
of the main airfoil section. Movement of the
control causes pressure changes on the
airfoil, and these pressure changes are felt on
the balance area.

A

Internal Balance

48
Q

The balance tab causes a
force to act on the control surface trailing
edge, which is opposite to the force on the
main control surface. The tab is geared to
move in the opposite direction to the control
surface whenever the control surface is
deflected. Unlike the previous types of
balance, the balance tab will give some
reduction in control effectiveness, as the tab
force is opposite to the control force.

A

Balance Tab

49
Q

The ________ is geared to move in the
same direction as the control surface, and so
will increase the control effectiveness, but of
course will increase the hinge moment and
give heavier stick forces.

A

anti-balance tab or anti-servo tab

50
Q

The purpose of the ________ is
to enable the pilot to move the control
surface easily. In this system, there is no
direct movement of the control surface as a
result of moving the cockpit control.

A

servo tab

51
Q

The_______ is a modification
of the balance tab, such that the tab
movement is proportional to the applied
stick force. Maximum assistance is therefore
obtained when the stick forces are greatest.
This is achieved by putting a spring in the
linkage to the tab. The spring tab is used
mainly to reduce control loads at high
airspeeds.

A

spring tab

52
Q

________ is a weight attached to the
control surface forward of the hinge. Most
control surfaces are __________. The
purpose of this is to prevent control surface
flutter.

A

mass balance ; mass balanced

53
Q

______ is an oscillation of the control surface
which can occur due to the bending and
twisting of the structure under load. If the
center of gravity of the control surface is
behind the hinge, its inertia causes it to
oscillate about its hinge when the structure
distorts. In certain circumstances the
oscillations can be divergent, and cause
failure of the structure.

A

Flutter

54
Q

The _____________ consist of lift
augmentation devices (flaps and slats), lift
dumping devices (spoilers except when they
are used for roll control), and air brakes and
trimming controls. Some or all of these
devices may be fitted to a particular aircraft

A

secondary flight controls

55
Q

The purpose of __________ is to
increase the lift generated by the wings at
low speed. They are normally only used for
takeoff and initial climb out, and approach
and landing.

A

trailing edge flaps

56
Q

These may consist of slats, Krueger flaps, or
variable camber flaps or some combination
as on the Boeing 747 which uses Krueger
flaps for the inboard section and variable
camber for the outboard and Boeing 737
which also uses Krueger flaps for the inboard
section and slats for the outboard section.

A

High Lift Devices Leading Edge