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### Vision at night. Disorientation. Hypoxia. 21. Night Vision ... making abilities, and cause a breakdown in scanning techniques and night vision. ... – PowerPoint PPT presentation

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Title: Weight

1
Lecture 13
• Weight Balance (Contd)
• Chapters 8, Jeppesen Sanderson
• Human Factors
• Chapters 10, Jeppesen Sanderson

2
Determining Total Weight CG
• Three ways to determine the center of Gravity
• Computation method
• Table method
• Graph method
• What we have gone through is the computation
method. It is the most accurate and thorough
approach. However calculation can make careless
mistakes, even with the calculator.
• Manufacturers provide tables and/or graphs to do
estimations to simplify things.

3
Computation method for finding CG
• The normal procedure is to find the total weight
first.
• If the total weight is already more than the
maximum weight limit, you will have to leave
• Once the total weight is within limit, calculate
the moments of the different items.
• The POH provides the approximate values for each
of the arms. (Fig 8-33a).
• Then complete a form (Fig 8-33b) listing the
calculations for the CG arm.
• Then check the CG range from the chart provided
in POH to see that the CG is within range.

4
Information for approximate arm lengths (8-33a)
5
Information for approximate arm lengths (8-33b)
6
Table method for finding CG
• The POH also provides moment tables with the
moments of typical items of the useful load
already calculated for you, assuming those items
are placed in their respective common locations.
Thus when you know the weights of those items you
can find their moments from the tables and do not
have to do the multiplication (Fig 8-34a).
• You still have to do the additions in finding the
total weight and the total moment.
• Once the total weight and the total moment are
known, you can again check from a table to see
that the total moment falls within the forward
and aft limits provided on the table (Fig 8-34b).

7
Moment table to find moments (8-34a)
8
Moment table to find moments (in 100 lb-in)
(8-34b)
9
Graph method for finding CG
• Similar to Table Method, however the values in
the tables are plotted in graphs.
• Values are therefore continuous instead of
discrete as in a table.
specific load item, e.g., pilot (and front seat
passenger or copilot), fuel, rear passengers,
baggage). Once you know the weights of those
items the graphs give you the moments of them
(Fig 8-35a).
• You still have to add up for the total weight and
the total moment.
• From the CG Moment Envelope graph you find out if
the total weight and moment you found would fall
into the accepted envelope (Fig 8-35b).

10
11
Checking if total moment is acceptable from CG
Moment Envelope graph (8-35b)
12
Weight Shifting (1)
• After finding the CG arm (or the CG moment) and
if it falls out of the acceptable limits you
might want to move some of the load in order to
move the CG into acceptable range.
• You can, of course, do this by trial and error
and repeat the whole process of finding the CG
arm with the new arrangement. However there are
quicker ways.
• If you move a certain weight (Weight Moved) by a
certain distance (Distance Between Arms), it will
produce a shift (change) of moment (Moment
Changed) equal to
• Moment Changed Weight Moved x Distance Between
Arms
• However this change is also equal to the total
Weight of the Airplane times the Distance the CG
has moved
• Moment Changed Weight of Airplane x Distance
CG Moves

13
Weight Shifting (2)
• Therefore
• Weight Moved x Distance Between Arms
• Weight of Airplane x Distance CG Moves
• From this, we get the Shift Equation
• Weight Moved Distance CG
Moves .
• Weight of Airplane Distance Between Arms
• Knowing any 3 of the values in the Shift
Equation, you can find the forth.

14
Weight Shifting (3)
• Fig 8-37 shows an example where you know that you
have to move the CG back by 2 inches in order to
bring the CG into the acceptable range. You also
know that you want to move a passenger from the
front seat to the back seat, which are 36 inches
from the front seat. The total weight of the
airplane is 2500 pounds. The question is about
how heavy a passenger you want to choose to move
from the front to the back.

15
Finding the weight you need to shift (8-37)
16
Weight Shifting (4)
• If after finding the CG, you decided that you
have to move a certain weight like a passenger or
a luggage, you can use the weight-shift formula
to find how much the CG will shift as shown in
Fig. 3-38.
• Notice that the formula does not tell you which
direction the CG will move so you have to keep
track of its direction by noting which direction
the weight has shifted.

17
Shifting an object with known weight (8-38)
18
Weight Shifting (5)
• With the Shift Equation, you can also calculate
the distance a certain weight you would need to
move in order to shift the CG by a certain
amount.
• Figure 8-39 is an example where the CG needs to
be moved by 1.5 inches. You decide to move a
piece of luggage which weighs 156 pounds. The
entire airplane weighs 2500 pounds. The question
is how far a distance the luggage has to be moved.

19
Finding how far a weight has to be moved to
produce a desired move in the CG (Fig 8-39)
20
Human Factors
• Factors of the human body that is affected by
aviation operation, or have an effect on flying
includes
• Vision at night
• Disorientation
• Hypoxia

21
Night Vision
• When we focus on an object in front of our eyes
we use some visual cells in the middle of our
retina called cones.
• However cones are not very sensitive if the light
is dim, like at night.
• Cells on the retina around the cones are much
more sensitive at night. These cells, which are
called rods, are up to 10,000 time more sensitive
than cones at night.
• However, you use rods to see things that are off
center.
• Therefore, at night, a pilot should look for
outside traffic by looking 5 to 10 degrees off
the center of his/her visual field, by scanning
for traffic instead of staring straight in front.

22
Disorientation (1)
to the environment.
• During flight, you may encounter situations where
the information is wrong or conflicting.
• Disorientation is an incorrect image of ones own
position, attitude, or movement.

23
Disorientation (2)
• Fatigue, anxiety, heavy workloads, and alcohol
increase your chances of having disorientation
and visual illusions.
• These factors increase response times, reduce
decision-making abilities, and cause a breakdown
in scanning techniques and night vision.
• We rely on three kinds of input for our
orientation
• Vision
• Kinesthetic sense
• Vestibular system in your inner ear

24
Disorientation (3)
• Kinesthetic sense is the feeling of pressure or
stretch from your skin, joints, and muscles.
• Kinesthetic sense can be unreliable because, for
example, it cannot tell the difference between
senses caused by gravity or by G-loads.
• During the day, the most important input for your
sense of orientation is from your vision, and you
supplement it with kinesthetic and vestibular
senses.
• But at night, or in IFR flight conditions, visual
sense is very limited. You have to rely more on
the other two less reliable senses, and therefore
scanning at your flight instruments often becomes
very important.

25
Disorientation (4)
• Vestibular senses come from the semi-circular
canals in your inner ears. It gives you a sense
when you are accelerating, decelerating, or
turning, including the motions of roll, pitch,
and yaw.
• However, the vestibular system also give some
people motion sickness.
• Passengers are especially affected more than
pilots because they often focus their attention
inside the plane instead of outside.
• Common symptoms of airsickness are general
discomfort, paleness, nausea, dizziness, and
vomiting.

26
Disorientation (5)
• If you are a flight crew member you can suggest
back of the chair and attempt to relax.

27
Hypoxia (1)
• Hypoxia is a condition when cells in your body
does not have enough oxygen supply.
• This comes as a result of high altitude flying
where air density gets low.
• Hypoxia is considered the most dangerous of all
physiological causes of accidents.
• It can come very suddenly at high altitudes, or
slowly at low altitudes for long period of
insufficient oxygen.

28
Hypoxia (2)
• If you suffer from hypoxia your judgment and
rationality may be seriously affected.
• At high altitude, when you suffer from hypoxia,
if you do not put on an oxygen mask within 10 to
20 seconds, you might not be able to put it on to
• You can increase your tolerance to hypoxia by
• Maintaining good physical condition
• Eating a nutritious diet
• Avoiding alcohol and smoking
• Avoid heavy physical activities
• Avoid temperature extremes

29
Hypoxia (3)
• If you are flying over 12,000 feet you should
check for the need of supplemental oxygen.
• Supplemental oxygen uses oxygen masks.
• Aircraft cabin pressurization increase air
pressure in the cabin using compressed air.
• However, at high altitude, if the pressurization
system fails, hypoxia occurs very fast unless you
use supplementary oxygen.