Lesson 14: Weight And Balance
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.
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).
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.
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).
Importance Of Weight And Balance
• Who has the final responsibility for accurate, up-to-date aircraft empty weight and Balance?
Importance Of Weight And Balance
• Who has the final responsibility for accurate, up-to-date aircraft empty weight and Balance?
Pilot
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.
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.
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
Determining the CG
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
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)
Weight And Balance Changes
• An A&P 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.
Top Related