The axes of an aircraft are three imaginary lines that pass through an aircraft’s CG. The axes can be considered as imaginary axles around which the aircraft turns. The three axes pass through the CG at 90° angles to each other. The axis passes through the CG and parallel to a line from nose to tail is the longitudinal axis, the axis that passes parallel to a line from wingtip to wingtip is the lateral axis, and the axis that passes through the CG at right angles to the other two axes is the vertical axis. Whenever an aircraft changes its flight attitude or position in flight, it rotates about one or more of the three axes.
2. c
c
Forces Acting on the
Aircraft
AGENDA Axes of anAircraft
01 02 03
c
Stability
and Control
3. Thrust - It is the force produced by the power
plant/propeller or rotor . It is the force that
acts opposite to overcome the force of
drag/weight..
01
Lift - It is the force that acts opposite to the
downward force of weight, is produced by
the dynamic effect of the air that moves
over the propeller airfoil.
02
Weight - It is the combined load of the
aircraft, weight pulls the aircraft
downward because of the force of gravity.
It opposes lift and acts vertically downward
through the aircraft's center of gravity (CG)
.
03
Forces Acting on
the Aircraft
01 02 03 04
Drag- Drag is the force that resists
movement of an aircraft through the
air.
04
4. c
The aircraft’s motion about its longitudinal axis
resembles the roll of a ship from side to side. In
fact, the names used to describe the motion about
an aircraft’s three axes were originally nautical
terms.
Axes of anAircraft
The axes of an aircraft are three imaginary lines that pass through
an aircraft’s CG. The axes can be considered as imaginary axles
around which the aircraft turns. The three axes pass through the CG
at 90° angles to each other. The axis passes through the CG and
parallel to a line from nose to tail is the longitudinal axis, the axis
that passes parallel to a line from wingtip to wingtip is the lateral
axis, and the axis that passes through the CG at right angles to the
other two axes is the vertical axis. Whenever an aircraft changes its
flight attitude or position in flight, it rotates about one or more of the
three axes.
01 02 03
5. M o t i o n s o f a c t
THE THREE MOTIONS ACTING ON
MULTIROTOR
1. ROLL – controlled by the ailerons,
2. PITCH – controlled by the elevators,
3. YAW – controlled by the rudder,
4. HEAVE – raise or decent of an aircraft
vertically,
5. LIST – tilting of aircraft side by side,
01 02 03
6. Stability and Control -
Discussion on Static and
Dynamic Stability
IStatic Stability if an airplane disturbed from equilibrium
state has “Initial Tendency” to return to its equilibrium state,
then the aircraft is assumed to have static stability.
Dynamic Stability Not only initial tendency, but also the
amplitudes of the response due to disturbance decay in
finite time to attain the equilibrium state.
In general, when aircraft is being referred to be in
stable equilibrium, we mean dynamic stability.
01 02 03
7. c
Static Stability
Static stability is the initial tendency of an aircraft to
return to its original position when it's disturbed.
There are three kinds of static stability:
Positive
Neutral
Negative
Positive Static Stability
An aircraft that has positive static stability tends to return
to its original attitude when it's disturbed. Let's say you're
flying an aircraft, you hit some turbulence, and the nose
pitches up. Immediately after that happens, the nose
lowers and returns to its original attitude. That's an
example positive static stability, and it's something you'd
see flying an airplane like a Cessna 172.
01 02 03
8. c
Neutral static stability
An aircraft that has neutral static stability tends to stay
in its new attitude when it's disturbed. For example, if
you hit turbulence and your nose pitches up 5
degrees, and then immediately after that it stays at 5
degrees nose up, your airplane has neutral static
stability.
Negative static stability
Finally, an aircraft that has negative static stability
tends to continue moving away from its original
attitude when it's disturbed. For example, if you hit
turbulence and your nose pitches up, and then
immediately continues pitching up, you're airplane has
negative static stability. For most aircraft, this is a very
undesirable thing.
01 02 03
c
9. c
Dynamic Stability
a)Dynamic stability refers to the aircraft response over a
period of time when disturbed from a given pitch, yaw, or
bank. This type of stability also has three subtypes and
are given below:
1.Positive dynamic stability - over a period of time, the
motion of the displaced object decreases in
amplitude and because it is positive, the object
displaced returns toward the equilibrium state.
2.Neutral dynamic stability - once displaced, the
displaced object neither decreases
nor increases in amplitude. A worn automobile shock
absorber makes this tendency.
3.Negative dynamic stability - over a period of time,
the motion of the displaced object increases and
becomes more divergent
01 02 03
