Lesson 14: Weight And Balance

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Lesson 14 Weight And Balance
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Importance Of Weight And Balance

• Forward CG
• Increases tail down force which increases
  effective weight (real weight tail down force)
• All parameters of aircraft performance will
  decrease except maximum power off glide distance.

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Importance Of Weight And Balance

• Forward CG
• Take off and landing distance and stall speed
  will increase, cruising speed and rate of climb
  will decrease.
• Control pressures for pitch changes will be
  greater.
• Pitch trim nose up
• Most dangerous part of flight with forward CG is
  landing (ground effect).

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Importance Of Weight And Balance

• Aft CG
• Decreases the need for tail down force so
  effective weight is less.
• Control changes for pitch changes will be light.
• Pitch stability will be poor.
• Stall speed decreases.

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Importance Of Weight And Balance

• Aft CG
• All performance parameters improve, except
  maximum power off glide distance.
• Most dangerous part of flight with aft CG occurs
  in slow flight (stall/spin may lead to flat
  spin).

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Importance Of Weight And Balance

• Who has the final responsibility for accurate,
  up-to-date aircraft empty weight and Balance?

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Importance Of Weight And Balance

• Who has the final responsibility for accurate,
  up-to-date aircraft empty weight and Balance?
• Pilot

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Importance Of Weight And Balance

• Any time equipment is added or removed, or any
  repair or alteration is made, this change must be
  recorded in the weight and balance information.
• Weight and balance information used by the pilot
  must be kept up to date.
• Done by maintenance technician.
• Referenced by the pilot for weight and balance
  calculations.

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Terminology

• Arm The horizontal distance of any object from
  the datum. Expressed in inches and may be or
  .
• Center of Gravity - The point at which the nose
  and tail moments are of equal magnitude (CG).
• Datum An imaginary vertical line from which all
  horizontal measurements are made or indicated.

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Terminology

• Moment A rotational force caused by a weight
  acting on an arm. The product of the weight
  multiplied by the arm.
• Weight X Arm Moment
• W X A M

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Determining the CG
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Determining the CG

• Moment Index
• Loading graph is used to determine the moment
  index
• Advantage No multiplication.
• Disadvantage Shows only the loaded CG.
• Figure 16-14 Loading graph
• Figure 16-15

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Terminology

• Ballast Weight used to obtain a favorable
  center of gravity location. It is often made of
  lead. It may be movable or permanent and must be
  marked as such.
• TOTAL WEIGHT X DISTANCE NEEDED TO SHIFT BP
• ARM OF BALLAST ARM OF NEW BP
• Figure 16-25 (Temporary Ballast)
• Figure 16-26 (Shifting Weight)

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Weight And Balance Changes

• An AP maintenance technician will have to find
  the new empty weight and empty weight center of
  gravity after an alteration to the aircraft has
  been performed.

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