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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

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

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.

Computation method for finding CG
  • The normal procedure is to find the total weight
  • If the total weight is already more than the
    maximum weight limit, you will have to leave
    something behind in your loading list.
  • 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.

Information for approximate arm lengths (8-33a)
Information for approximate arm lengths (8-33b)
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).

Moment table to find moments (8-34a)
Moment table to find moments (in 100 lb-in)
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.
  • Each curve on the Loading Graph represents a
    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).

Finding moments from loading graph (8-35a)
Checking if total moment is acceptable from CG
Moment Envelope graph (8-35b)
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
  • 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

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.

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.

Finding the weight you need to shift (8-37)
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.

Shifting an object with known weight (8-38)
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
  • 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.

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

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
  • 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.

Disorientation (1)
  • Sensory organs of your body provide your brain
    with information about your orientation , i.e.,
    about your body position and motion in relation
    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.

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
  • Vision
  • Kinesthetic sense
  • Vestibular system in your inner ear

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
  • 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.

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

Disorientation (5)
  • If you are a flight crew member you can suggest
    that your passengers put their heads back on the
    back of the chair and attempt to relax.

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.

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
    your face.
  • 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

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.
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